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PDF file - 8K, Table S1. TERT promoter mutation status in 59 pTa and 17 carcinoma in situ (CIS) patients.

A real-time trial of a cancer blood test Cancers diagnosed early are often more responsive to treatment. Blood tests that detect molecular markers of cancer have successfully identified individuals already known to have the disease. Lennon et al. conducted an exploratory study that more closely reflects the way in which such blood tests would be used in the future. They evaluated the feasibility and safety of incorporating a multicancer blood test into the routine clinical care of 10,000 women with no history of cancer. Over a 12-month period, the blood test detected 26 cancers of different types. A combination of the blood test and positron emission tomography–computed tomography (PET-CT) imaging led to surgical removal of nine of these cancers. Use of the blood test did not result in a large number of futile follow-up procedures. Science , this issue p. eabb9601

Aneuploidy is a feature of most cancer cells, and a myriad of approaches have been developed to detect it in clinical samples. We previously described primers that could be used to amplify ∼38,000 unique long interspersed nucleotide elements (LINEs) from throughout the genome. Here we have developed an approach to evaluate the sequencing data obtained from these amplicons. This approach, called Within-Sample AneupLoidy DetectiOn (WALDO), employs supervised machine learning to detect the small changes in multiple chromosome arms that are often present in cancers. We used WALDO to search for chromosome arm gains and losses in 1,677 tumors and in 1,522 liquid biopsies of blood from cancer patients or normal individuals. Aneuploidy was detected in 95% of cancer biopsies and in 22% of liquid biopsies. Using single-nucleotide polymorphisms within the amplified LINEs, WALDO concomitantly assesses allelic imbalances, microsatellite instability, and sample identification. WALDO can be used on samples containing only a few nanograms of DNA and as little as 1% neoplastic content and has a variety of applications in cancer diagnostics and forensic science.

ObjectiveFor patients with locally advanced rectal cancer (LARC), adjuvant chemotherapy selection following surgery remains a major clinical dilemma. Here, we investigated the ability of circulating tumour DNA (ctDNA) to improve risk stratification in patients with LARC.DesignWe enrolled patients with LARC (T3/T4 and/or N+) planned for neoadjuvant chemoradiotherapy. Plasma samples were collected pretreatment, postchemoradiotherapy and 4–10 weeks after surgery. Somatic mutations in individual patient’s tumour were identified via massively parallel sequencing of 15 genes commonly mutated in colorectal cancer. We then designed personalised assays to quantify ctDNA in plasma samples. Patients received adjuvant therapy at clinician discretion, blinded to the ctDNA results.ResultsWe analysed 462 serial plasma samples from 159 patients. ctDNA was detectable in 77%, 8.3% and 12% of pretreatment, postchemoradiotherapy and postsurgery plasma samples. Significantly worse recurrence-free survival was seen if ctDNA was detectable after chemoradiotherapy (HR 6.6; PConclusionPostoperative ctDNA analysis stratifies patients with LARC into subsets that are either at very high or at low risk of recurrence, independent of conventional clinicopathological risk factors. ctDNA analysis could potentially be used to guide patient selection for adjuvant chemotherapy.

Current non-invasive approaches for detection of urothelial cancers are suboptimal. We developed a test to detect urothelial neoplasms using DNA recovered from cells shed into urine. UroSEEK incorporates massive parallel sequencing assays for mutations in 11 genes and copy number changes on 39 chromosome arms. In 570 patients at risk for bladder cancer (BC), UroSEEK was positive in 83% of those who developed BC. Combined with cytology, UroSEEK detected 95% of patients who developed BC. Of 56 patients with upper tract urothelial cancer, 75% tested positive by UroSEEK, including 79% of those with non-invasive tumors. UroSEEK detected genetic abnormalities in 68% of urines obtained from BC patients under surveillance who demonstrated clinical evidence of recurrence. The advantages of UroSEEK over cytology were evident in low-grade BCs; UroSEEK detected 67% of cases whereas cytology detected none. These results establish the foundation for a new non-invasive approach for detection of urothelial cancer.

Somatic activating mutations in the promoter of the telomerase reverse transcriptase (TERT) gene are the most common genetic alterations in urothelial carcinoma (UC) of the bladder and upper urinary tract. Little is known, however, about TERT-mutation status in the relatively uncommon but clinically aggressive micropapillary (MPC) variant. We evaluated the presence of TERT promoter mutations in MPC of the bladder and upper urinary tract. A retrospective search of our archives for MPC and UC with micropapillary features (2005–2014) was performed. All slides were reviewed to confirm the histologic diagnosis. Thirty-three specimens from 31 patients had FFPE blocks available for DNA analysis and were included in the study. Intratumoral areas of non-micropapillary histology were also evaluated when present. Samples were analyzed with Safe-SeqS, a sequencing error reduction technology, and sequenced using the Illumina MiSeq platform. TERT promoter mutations were detected in all specimens with pure MPC (18 of 18) and UC with focal micropapillary features (15 of 15). Similar to conventional UC, the predominant mutations identified occurred at positions −124 (C228T) (85 %) and −146 (C250T) (12 %) bp upstream of the TERT ATG start site. In heterogeneous tumors with focal variant histology, intratumoral concordant mutations were found in variant (MPC and non-MPC) and corresponding conventional UC. We found TERT promoter mutations, commonly found in conventional UC, to be frequently present in MPC. Our finding of concordant intratumoral mutational alterations in cases with focal variant histology lends support to the common oncogenesis origin of UC and its variant histology.

TERT promoter mutations (TERT-mut) have been detected in 60% to 80% of urothelial carcinomas. A molecular urine-based screening assay for the detection of TERT-mut is currently being pursued by our group and others. A small but significant number of bladder carcinomas are adenocarcinoma. The current study assesses the incidence of TERT-mut in primary adenocarcinomas of urinary bladder. A retrospective search of our institutional pathology records identified 23 cystectomy specimens with a diagnosis of adenocarcinoma (2000–2014). All slides were reviewed by a senior urologic pathologist to confirm tumor type and select a representative formalin-fixed, paraffin-embedded block for mutational analysis. Adequate material for DNA testing was available in 14 cases (7 enteric type and 7 not otherwise specified). TERT-mut sequencing analysis was performed using previously described SafeSeq technique. Overall, 28.5% of primary adenocarcinoma harbored TERT-mut. Interestingly, 57% of nonenteric adenocarcinomas were mutation positive, whereas none of the enteric-type tumors harbored mutations. Similar to urothelial carcinoma, we found a relatively higher rate of TERT-mut among nonenteric-type adenocarcinomas further supporting the potential utility of TERT-mut urine-based screening assay for bladder cancer.

Purpose Type II ovarian cancer (OC) and endometrial cancer (EC) are generally diagnosed at an advanced stage, translating into a poor survival rate. There is increasing evidence that Müllerian duct cancers may exfoliate cells. We have established an approach for lavage of the uterine cavity to detect shed cancer cells. Patients and Methods Lavage of the uterine cavity was used to obtain samples from 65 patients, including 30 with OC, five with EC, three with other malignancies, and 27 with benign lesions involving gynecologic organs. These samples, as well as corresponding tumor tissue, were examined for the presence of somatic mutations using massively parallel sequencing (next-generation sequencing) and, in a subset, singleplex analysis. Results The lavage technique could be applied successfully, and sufficient amounts of DNA were obtained in all patients. Mutations, mainly in TP53, were identified in 18 (60%) of 30 lavage samples of patients with OC using next-generation sequencing. Singleplex analysis of mutations previously determined in corresponding tumor tissue led to further identification of six patients. Taken together, in 24 (80%) of 30 patients with OC, specific mutations could be identified. This also included one patient with occult OC. All five analyzed lavage specimens from patients with EC harbored mutations. Eight (29.6%) of 27 patients with benign lesions tested positive for mutations, six (75%) as a result of mutations in the KRAS gene. Conclusion This study proved that tumor cells from ovarian neoplasms are shed and can be collected via lavage of the uterine cavity. Detection of OC and EC and even clinically occult OC was achieved, making it a potential tool of significant promise for early diagnosis.

Background & Aims The management of pancreatic cysts poses challenges to both patients and their physicians. We investigated whether a combination of molecular markers and clinical information could improve the classification of pancreatic cysts and management of patients. Methods We performed a multi-center, retrospective study of 130 patients with resected pancreatic cystic neoplasms (12 serous cystadenomas, 10 solid pseudopapillary neoplasms, 12 mucinous cystic neoplasms, and 96 intraductal papillary mucinous neoplasms). Cyst fluid was analyzed to identify subtle mutations in genes known to be mutated in pancreatic cysts ( BRAF , CDKN2A , CTNNB1 , GNAS , KRAS , NRAS , PIK3CA , RNF43 , SMAD4 , TP53 , and VHL ); to identify loss of heterozygozity at CDKN2A , RNF43 , SMAD4 , TP53 , and VHL tumor suppressor loci; and to identify aneuploidy. The analyses were performed using specialized technologies for implementing and interpreting massively parallel sequencing data acquisition. An algorithm was used to select markers that could classify cyst type and grade. The accuracy of the molecular markers was compared with that of clinical markers and a combination of molecular and clinical markers. Results We identified molecular markers and clinical features that classified cyst type with 90%−100% sensitivity and 92%−98% specificity. The molecular marker panel correctly identified 67 of the 74 patients who did not require surgery and could, therefore, reduce the number of unnecessary operations by 91%. Conclusions We identified a panel of molecular markers and clinical features that show promise for the accurate classification of cystic neoplasms of the pancreas and identification of cysts that require surgery.

Summary Activating mutations in the promoter of the telomerase reverse transcriptase (TERT) gene are the most common genetic alterations in urothelial carcinoma (UC) of the bladder and upper urinary tract. Although the cadherin 1 (CDH1) gene is commonly mutated in the clinically aggressive plasmacytoid variant of urothelial carcinoma (PUC), little is known about their TERT promoter mutation status. A retrospective search of our archives for PUC and UC with plasmacytoid and/or signet ring cell features (2007-2014) was performed. Ten specimens from 10 patients had archived material available for DNA analysis and were included in the study. Intratumoral areas of nonplasmacytoid histology were also evaluated when present. Samples were analyzed for TERT promoter mutations with Safe-SeqS, a sequencing error-reduction technology, and sequenced using a targeted panel of the 10 most commonly mutated genes in bladder cancer on the Illumina MiSeq platform. TERT promoter mutations were detected in specimens with pure and focal plasmacytoid features (6/10). Similar to conventional UC, the predominant mutation identified was g.1295228C>T. In heterogeneous tumors with focal variant histology, concordant mutations were found in plasmacytoid and corresponding conventional, glandular, or sarcomatoid areas. Co-occurring mutations in tumor protein p53 (TP53, 2 cases) and kirsten rat sarcoma (KRAS) viral proto-oncogene (1 case) were also detected. TERT promoter mutations are frequently present in PUC, which provides further evidence that TERT promoter mutations are common events in bladder cancer, regardless of histologic subtype, and supports their inclusion in any liquid biopsy assay for bladder cancer.

We report the detection of endometrial and ovarian cancers based on genetic analyses of DNA recovered from the fluids obtained during a routine Papanicolaou (Pap) test. The new test, called PapSEEK, incorporates assays for mutations in 18 genes as well as an assay for aneuploidy. In Pap brush samples from 382 endometrial cancer patients, 81% [95% confidence interval (CI), 77 to 85%] were positive, including 78% of patients with early-stage disease. The sensitivity in 245 ovarian cancer patients was 33% (95% CI, 27 to 39%), including 34% of patients with early-stage disease. In contrast, only 1.4% of 714 women without cancer had positive Pap brush samples (specificity, ~99%). Next, we showed that intrauterine sampling with a Tao brush increased the detection of malignancy over endocervical sampling with a Pap brush: 93% of 123 (95% CI, 87 to 97%) patients with endometrial cancer and 45% of 51 (95% CI, 31 to 60%) patients with ovarian cancer were positive, whereas none of the samples from 125 women without cancer were positive (specificity, 100%). Finally, in 83 ovarian cancer patients in whom plasma was available, circulating tumor DNA was found in 43% of patients (95% CI, 33 to 55%). When plasma and Pap brush samples were both tested, the sensitivity for ovarian cancer increased to 63% (95% CI, 51 to 73%). These results demonstrate the potential of mutation-based diagnostics to detect gynecologic cancers at a stage when they are more likely to be curable.

Current non-invasive approaches for detection of urothelial cancers are suboptimal. We developed a test to detect urothelial neoplasms using DNA recovered from cells shed into urine. UroSEEK incorporates massive parallel sequencing assays for mutations in 11 genes and copy number changes on 39 chromosome arms. In 570 patients at risk for bladder cancer (BC), UroSEEK was positive in 83% of those who developed BC. Combined with cytology, UroSEEK detected 95% of patients who developed BC. Of 56 patients with upper tract urothelial cancer, 75% tested positive by UroSEEK, including 79% of those with non-invasive tumors. UroSEEK detected genetic abnormalities in 68% of urines obtained from BC patients under surveillance who demonstrated clinical evidence of recurrence. The advantages of UroSEEK over cytology were evident in low-grade BCs; UroSEEK detected 67% of cases whereas cytology detected none. These results establish the foundation for a new non-invasive approach for detection of urothelial cancer.

Current non-invasive approaches for bladder cancer (BC) detection are suboptimal. We report the development of non-invasive molecular test for BC using DNA recovered from cells shed into urine. This “UroSEEK” test incorporates assays for mutations in 11 genes and copy number changes on 39 chromosome arms. We first evaluated 570 urine samples from patients at risk for BC (microscopic hematuria or dysuria). UroSEEK was positive in 83% of patients that developed BC, but in only 7% of patients who did not develop BC. Combined with cytology, 95% of patients that developed BC were positive. We then evaluated 322 urine samples from patients soon after their BCs had been surgically resected. UroSEEK detected abnormalities in 66% of the urine samples from these patients, sometimes up to 4 years prior to clinical evidence of residual neoplasia, while cytology was positive in only 25% of such urine samples. The advantages of UroSEEK over cytology were particularly evident in low-grade tumors, wherein cytology detected none while UroSEEK detected 67% of 49 cases. These results establish the foundation for a new, non-invasive approach to the detection of BC in patients at risk for initial or recurrent disease.

Upper tract urothelial carcinomas (UTUC) of the renal pelvis or ureter can be difficult to detect and challenging to diagnose. Here, we report the development and application of a non-invasive test for UTUC based on molecular analyses of DNA recovered from cells shed into the urine. The test, called UroSEEK, incorporates assays for mutations in eleven genes frequently mutated in urologic malignancies and for allelic imbalances on 39 chromosome arms. At least one genetic abnormality was detected in 75% of urinary cell samples from 56 UTUC patients but in only 0.5% of 188 samples from healthy individuals. The assay was considerably more sensitive than urine cytology, the current standard-of-care. UroSEEK therefore has the potential to be used for screening or to aid in diagnosis in patients at increased risk for UTUC, such as those exposed to herbal remedies containing the carcinogen aristolochic acid.

Early indicators of treatment response in metastatic colorectal cancer (mCRC) could conceivably be used to optimize treatment. We explored early changes in circulating tumor DNA (ctDNA) levels as a marker of therapeutic efficacy.This prospective study involved 53 mCRC patients receiving standard first-line chemotherapy. Both ctDNA and CEA were assessed in plasma collected before treatment, 3 days after treatment and before cycle 2. Computed tomography (CT) scans were carried out at baseline and 8-10 weeks and were centrally assessed using RECIST v1.1 criteria. Tumors were sequenced using a panel of 15 genes frequently mutated in mCRC to identify candidate mutations for ctDNA analysis. For each patient, one tumor mutation was selected to assess the presence and the level of ctDNA in plasma samples using a digital genomic assay termed Safe-SeqS.Candidate mutations for ctDNA analysis were identified in 52 (98.1%) of the tumors. These patient-specific candidate tissue mutations were detectable in the cell-free DNA from the plasma of 48 of these 52 patients (concordance 92.3%). Significant reductions in ctDNA (median 5.7-fold; P0.001) levels were observed before cycle 2, which correlated with CT responses at 8-10 weeks (odds ratio = 5.25 with a 10-fold ctDNA reduction; P = 0.016). Major reductions (≥10-fold) versus lesser reductions in ctDNA precycle 2 were associated with a trend for increased progression-free survival (median 14.7 versus 8.1 months; HR = 1.87; P = 0.266).ctDNA is detectable in a high proportion of treatment naïve mCRC patients. Early changes in ctDNA during first-line chemotherapy predict the later radiologic response.

Cell-free DNA shed by cancer cells has been shown to be a rich source of putative tumor-specific biomarkers. Because cell-free DNA from brain and spinal cord tumors cannot usually be detected in the blood, we studied whether the cerebrospinal fluid (CSF) that bathes the CNS is enriched for tumor DNA, here termed CSF-tDNA. We analyzed 35 primary CNS malignancies and found at least one mutation in each tumor using targeted or genome-wide sequencing. Using these patient-specific mutations as biomarkers, we identified detectable levels of CSF-tDNA in 74% [95% confidence interval (95% CI) = 57-88%] of cases. All medulloblastomas, ependymomas, and high-grade gliomas that abutted a CSF space were detectable (100% of 21 cases; 95% CI = 88-100%), whereas no CSF-tDNA was detected in patients whose tumors were not directly adjacent to a CSF reservoir (P0.0001, Fisher's exact test). These results suggest that CSF-tDNA could be useful for the management of patients with primary tumors of the brain or spinal cord.

To investigate whether tumor cells could be detected in the vagina of women with serous ovarian cancer through TP53 analysis of DNA samples collected by placement of a vaginal tampon.Women undergoing surgery for a pelvic mass were identified in the gynecologic oncology clinic. They placed a vaginal tampon before surgery, which was removed in the operating room. Cells were isolated and DNA was extracted from both the cells trapped within the tampon and the primary tumor. In patients with serous carcinoma, the DNA was interrogated for the presence of TP53 mutations using a method capable of detecting rare mutant alleles in a mixture of mutant and wild-type DNA.Thirty-three patients were enrolled. Eight patients with advanced serous ovarian cancer were included for analysis. Three had a prior tubal ligation. TP53 mutations were identified in all eight tumor samples. Analysis of the DNA from the tampons revealed mutations in three of the five patients with intact tubes (sensitivity 60%) and in none of the three patients with tubal ligation. In all three participants with mutation detected in the tampon specimen, the tumor and the vaginal DNA harbored the exact same TP53 mutation. The fraction of DNA derived from exfoliated tumor cells ranged from 0.01% to 0.07%.In this pilot study, DNA derived from tumor was detected in the vaginas of 60% of patients with ovarian cancer with intact fallopian tubes. With further development, this approach may hold promise for the early detection of this deadly disease.

Importance For patients with resected, nonmetastatic colorectal cancer (CRC), the optimal surveillance protocol remains unclear. Objective To evaluate whether serial circulating tumor DNA (ctDNA) levels detected disease recurrence earlier, compared with conventional postoperative surveillance, in patients with resected CRC. Design, Setting, and Participants This study included patients (n = 58) with stage I, II, or III CRC who underwent radical surgical resection at 4 Swedish hospitals from February 2, 2007, to May 8, 2013. Eighteen patients received adjuvant chemotherapy at the discretion of their clinicians, who were blinded to the ctDNA results. Blood samples were collected at 1 month after the surgical procedure and every 3 to 6 months thereafter for ctDNA analysis. Patients were followed up until metachronous metastases were detected, or for a median of 49 months. Data analysis was performed from March 1, 2009, to June 23, 2018. Main Outcomes and Measures Sensitivity and timing of ctDNA positivity were compared with those of conventional surveillance modalities (computed tomographic scans and serum carcinoembryonic antigen tests) for the detection of disease recurrence. Results This study included 319 blood samples from 58 patients, with a median (range) age of 69 (47-83) years and 34 males (59%). The recurrence rate among patients with positive ctDNA levels was 77% (10 of 13 patients). Positive ctDNA preceded radiologic and clinical evidence of recurrence by a median of 3 months. Of the 45 patients with negative ctDNA throughout follow-up, none (0%; 95% CI, 0%-7.9%) experienced a relapse, with a median follow-up of 49 months. However, 3 (6%; 95% CI, 1.3%-17%) of the 48 patients without relapse had a positive ctDNA result, which subsequently fell to undetectable levels during follow-up. Conclusion and Relevance Although these findings need to be validated in a larger, prospective trial, they suggest that ctDNA analysis could complement conventional surveillance strategies as a triage test to stratify patients with resected CRC on the basis of risk of disease recurrence.

Bone and soft tissue sarcomas are a group of histologically heterogeneous and relatively uncommon tumors. To explore their genetic origins, we sequenced the exomes of 13 osteosarcomas, eight myxoid liposarcomas (MLPS), and seven synovial sarcomas (SYN). These tumors had few genetic alterations (median of 10.8). Nevertheless, clear examples of driver gene mutations were observed, including canonical mutations in TP53, PIK3CA, SETD2, AKT1, and subclonal mutation in FBXW7. Of particular interest were mutations in H3F3A, encoding the variant histone H3.3. Mutations in this gene have only been previously observed in gliomas. Loss of heterozygosity of exomic regions was extensive in osteosarcomas but rare in SYN and MLPS. These results provide intriguing nucleotide-level information on these relatively uncommon neoplasms and highlight pathways that help explain their pathogenesis.

We present the bottleneck sequencing system (BotSeqS), a next-generation sequencing method that simultaneously quantifies rare somatic point mutations across the mitochondrial and nuclear genomes. BotSeqS combines molecular barcoding with a simple dilution step immediately before library amplification. We use BotSeqS to show age- and tissue-dependent accumulations of rare mutations and demonstrate that somatic mutational burden in normal human tissues can vary by several orders of magnitude, depending on biologic and environmental factors. We further show major differences between the mutational patterns of the mitochondrial and nuclear genomes in normal tissues. Lastly, the mutation spectra of normal tissues were different from each other, but similar to those of the cancers that arose in them. This technology can provide insights into the number and nature of genetic alterations in normal tissues and can be used to address a variety of fundamental questions about the genomes of diseased tissues.

We determined whether the mutations found in ovarian cancers could be identified in the patients' ovarian cyst fluids. Tumor-specific mutations were detectable in the cyst fluids of 19 of 23 (83%) borderline tumors, 10 of 13 (77%) type I cancers, and 18 of 18 (100%) type II cancers. In contrast, no mutations were found in the cyst fluids of 18 patients with benign tumors or non-neoplastic cysts. Though large, prospective studies are needed to demonstrate the safety and clinical utility of this approach, our results suggest that the genetic evaluation of cyst fluids might be able to inform the management of the large number of women with these lesions. DOI: http://dx.doi.org/10.7554/eLife.15175.001, eLife digest More than a third of women develop ovarian cysts during their lifetimes. The vast majority of these cysts are harmless, but a small number are caused by ovarian cancers. These cancers often produce no symptoms until the disease has spread throughout the abdomen or to other organs, so many women go undiagnosed until their chances of being successfully treated are low. Currently, there is no reliable way to determine whether an ovarian cyst is cancerous without performing surgery. As a result, many women undergo unnecessary, invasive surgeries for harmless ovarian cysts. Tumors shed cells and cell fragments into any fluid that surrounds them. Fluids from cysts in the pancreas, kidney, and thyroid are routinely examined to identify whether they contain cancerous cells. Now, Wang, Sundfeldt et al. show that ovarian cancers also shed DNA into the surrounding cyst fluid. Furthermore, mutations found in this DNA can provide valuable information about whether the cysts are cancerous. The study was performed by extracting DNA from the fluid in ovarian cysts that had been surgically removed from 77 women. Of these cysts, 10 were harmless cysts, 12 were benign tumors, 31 were invasive cancers, and 24 were so-called borderline tumors, which fall somewhere between the benign tumors and invasive cancers. Only cysts associated with the borderline tumors and invasive cancers need to be surgically removed. Here, Wang, Sundfeldt et al. report that DNA mutations that are characteristic of ovarian cancers were found in 87% of the cysts associated with borderline tumors and invasive cancers. In contrast, these mutations were not found in any of the cysts that do not require surgery. Fluid can be extracted from an ovarian cyst with a needle during an outpatient visit. Therefore, the results presented by Wang, Sundfeldt et al. suggest a relatively straightforward way of testing the DNA from ovarian cysts before deciding whether surgery is really necessary. First, however, larger studies that follow women with cysts over time will be necessary to confirm that this type of testing is effective and safe. DOI: http://dx.doi.org/10.7554/eLife.15175.002

Detection of circulating tumor DNA (ctDNA) after resection of stage II colon cancer may identify patients at the highest risk of recurrence and help inform adjuvant treatment decisions. We used massively parallel sequencing–based assays to evaluate the ability of ctDNA to detect minimal residual disease in 1046 plasma samples from a prospective cohort of 230 patients with resected stage II colon cancer. In patients not treated with adjuvant chemotherapy, ctDNA was detected postoperatively in 14 of 178 (7.9%) patients, 11 (79%) of whom had recurred at a median follow-up of 27 months; recurrence occurred in only 16 (9.8 %) of 164 patients with negative ctDNA [hazard ratio (HR), 18; 95% confidence interval (CI), 7.9 to 40; P < 0.001]. In patients treated with chemotherapy, the presence of ctDNA after completion of chemotherapy was also associated with an inferior recurrence-free survival (HR, 11; 95% CI, 1.8 to 68; P = 0.001). ctDNA detection after stage II colon cancer resection provides direct evidence of residual disease and identifies patients at very high risk of recurrence.

TERT promoter mutations (TERT-mut) are detectable in the majority of urothelial carcinomas. The detection of TERT-mut in urine is under investigation as a potential urine-based molecular-screening assay for bladder cancer. A small but significant number of bladder carcinomas are pure squamous cell carcinoma. We sought to assess the incidence of TERT-mut in squamous cell carcinoma of the urinary bladder. A retrospective search of the institutional pathology archives yielded 15 cystectomy specimens performed for squamous cell carcinoma (2000–2014). Histologic slides were reviewed by a senior urologic pathologist to confirm the diagnosis and select a representative formalin-fixed paraffin-embedded tissue block for mutational analysis. All cases yielded adequate material for DNA analysis. Sequencing for TERT-mut was performed using previously described SafeSeq technique. We detected TERT-mut in 12/15 (80%) of bladder squamous cell carcinomas. TERT promoter mutations, commonly found in conventional urothelial carcinoma, are also highly prevalent in urinary bladder squamous cell carcinoma suggesting a common tumorigenesis and potential utility as a molecular urine-based-screening assay.

Colorectal tumors that are wild-type (WT) for KRAS are often sensitive to EGFR blockade, but almost always develop resistance within several months of initiating therapy1,2. The mechanisms underlying this acquired resistance to anti-EGFR antibodies are largely unknown. This situation stands in marked contrast to that of small molecule targeted agents, such as inhibitors of ABL, EGFR, BRAF, and MEK, in which mutations in the genes encoding the protein targets render the tumors resistant to the effects of the drugs3–6. The simplest hypothesis to account for the development of resistance to EGFR blockade are that rare cells with KRAS mutations pre-exist at low levels in tumors with ostensibly WT KRAS genes. Though this hypothesis would seem readily testable, there is no evidence in pre-clinical models to support it, nor is there data from patients. To test this hypothesis, we determined whether mutant KRAS DNA could be detected in the circulation of 28 patients receiving monotherapy with panitumumab, a therapeutic anti-EGFR antibody. We found that nine of 24 (38%) patients whose tumors were initially KRAS WT developed detectable mutations in KRAS in their sera, three of which developed multiple different KRAS mutations. The appearance of these mutations was very consistent, generally occurring between five to six months following treatment. Mathematical modeling indicated that the mutations were present in expanded subclones prior to the initiation of panitumumab. These results suggest that the emergence of KRAS mutations is a mediator of acquired resistance to EGFR blockade and that these mutations can be detected in a non-invasive manner. Moreover, they explain why solid tumors develop resistance to targeted therapies in a highly reproducible fashion.

The identification of mutations that are present in a small fraction of DNA templates is essential for progress in several areas of biomedical research. Although massively parallel sequencing instruments are in principle well suited to this task, the error rates in such instruments are generally too high to allow confident identification of rare variants. We here describe an approach that can substantially increase the sensitivity of massively parallel sequencing instruments for this purpose. The keys to this approach, called the Safe - Seq uencing S ystem (“Safe-SeqS”), are ( i ) assignment of a unique identifier (UID) to each template molecule, ( ii ) amplification of each uniquely tagged template molecule to create UID families, and ( iii ) redundant sequencing of the amplification products. PCR fragments with the same UID are considered mutant (“supermutants”) only if ≥95% of them contain the identical mutation. We illustrate the utility of this approach for determining the fidelity of a polymerase, the accuracy of oligonucleotides synthesized in vitro, and the prevalence of mutations in the nuclear and mitochondrial genomes of normal cells.

antiviral assembly inhibitor N-(3-chloro-4-methylphenyl)-N′-{2-[({5[(dimethylamino)-methyl]-2-furyl}-methyl)-sulfanyl]ethyl}-urea) (CAP-1) using a combination of NMR spectroscopy and X-ray crystallography. The protein undergoes a remarkable conformational change upon CAP-1 binding, in which Phe32 is displaced from its buried position in the protein core to open a deep hydrophobic cavity that serves as the ligand binding site. The aromatic ring of CAP-1 inserts into the cavity, with the urea NH groups forming hydrogen bonds with the backbone oxygen of Val59 and the dimethylamonium group interacting with the side-chains of Glu28 and Glu29. Elements that could be exploited to improve binding affinity are apparent in the structure. The displacement of Phe32 by CAP-1 appears to be facilitated by a strained main-chain conformation, which suggests a potential role for a Phe32 conformational switch during normal capsid assembly.

The myristoylated matrix protein (myr-MA) of HIV functions as a regulator of intracellular localization, targeting the Gag precursor polyprotein to lipid rafts in the plasma membrane during virus assembly and dissociating from the membrane during infectivity for nuclear targeting of the preintegration complex. Membrane release is triggered by proteolytic cleavage of Gag, and it has, until now, been believed that proteolysis induces a conformational change in myr-MA that sequesters the myristyl group. NMR studies reported here reveal that myr-MA adopts myr-exposed [myr(e)] and -sequestered [myr(s)] states, as anticipated. Unexpectedly, the tertiary structures of the protein in both states are very similar, with the sequestered myristyl group occupying a cavity that requires only minor conformational adjustments for insertion. In addition, myristate exposure is coupled with trimerization, with the myristyl group sequestered in the monomer and exposed in the trimer ( K assoc = 2.5 ± 0.6 × 10 8 M –2 ). The equilibrium constant is shifted ≈20-fold toward the trimeric, myristate-exposed species in a Gag-like construct that includes the capsid domain, indicating that exposure is enhanced by Gag subdomains that promote self-association. Our findings indicate that the HIV-1 myristyl switch is regulated not by mechanically induced conformational changes, as observed for other myristyl switches, but instead by entropic modulation of a preexisting equilibrium.

3521 Background: The optimal approach to adjuvant chemotherapy for rectal cancer is keenly debated. Routine practice and clinical guidelines vary widely. After pre-operative chemoradiation (CRT), a pathologic complete response (pCR) or nodal involvement (pN+) are prognostic markers that can guide clinical decision-making, but markers that better define the patients (pts) that are likely or unlikely to benefit from chemotherapy are urgently needed. We investigated the potential role of ctDNA as a biomarker to guide therapy. Methods: We conducted a prospective, multi-centre study in pts with LARC (T3/T4 and/or N+) planned for CRT and curative resection. Serial plasma samples were collected pre-CRT, post-CRT, and 4-10 weeks after surgery. Somatic mutations in individual pts’ tumor were identified via sequencing of 15 genes commonly mutated in colorectal cancers. We then designed personalized assays to quantify ctDNA in plasma samples. Pts received adjuvant therapy at clinician discretion. Results: 200 pts were enrolled between Apr-2012 and Dec-2015. Median age was 62 years (range 28-86), 67% were male and 159 pts had pre-CRT and post-op ctDNA samples available for analysis. Of these, 122 (77%) pts had detectable ctDNA prior to therapy. After surgery, 19 pts had detectable ctDNA and 11 of these 19 (58%) have recurred during a median follow up of 22 months. Recurrence occurred in only 12 of 140 (8.6%) with negative ctDNA (HR 12, p < 0.001). One hundred and two (64%) pts received adjuvant chemotherapy. Post-op ctDNA detection was predictive of recurrence irrespective of adjuvant chemotherapy (chemo: HR 10, p < 0.001; no chemo: HR 16, p < 0.001). Thirty-four pts (21%) achieved a pCR, 43 (27%) had pN+ disease. pCR (vs non-pCR) was associated with a trend for lower recurrence risk (HR 0.31, p = 0.089) and pN+ (vs pN0) with a higher recurrence risk (HR 4.2, p < 0.001). ctDNA detection remained predictive of recurrence among pts with a pCR (HR 14, p = 0.014) or with pN+ disease (HR 11, p < 0.001). Conclusions: Post-op ctDNA analysis stratifies pts with LARC into very high and low risk groups. ctDNA analysis remains strongly predictive of recurrence among pts with both lower risk (pCR) and higher risk (pN+) disease.

Cancer Immunosurveillance Gone Bad? A subset of patients who develop scleroderma, a debilitating autoimmune disease, have an elevated risk of developing cancer. These patients harbor autoantibodies to RPC1, an RNA polymerase subunit encoded by the POLR3A gene. Joseph et al. (p. 152 , published online December 5; see the Perspective by Teng and Smyth ) explored whether the RPC1 autoantibodies target a “foreign” antigen derived from a mutated POLR3A gene. Sequence analysis revealed that POLR3A mutations were present in tumors from six of eight patients with RPC1 autoantibodies but in no tumors from eight control patients who lacked RPC1 autoantibodies. Cell culture data suggested that the POLR3A mutations triggered cellular and humoral immune responses in the patients. These results provide support for the “immunosurveillance” hypothesis, which posits the continual eradication of nascent tumor cells via immune responses.

Papanicolaou (Pap) smears have revolutionized the management of patients with cervical cancers by permitting the detection of early, surgically curable tumors and their precursors. In recent years, the traditional Pap smear has been replaced by a liquid-based method, which allows not only cytologic evaluation but also collection of DNA for detection of human papillomavirus, the causative agent of cervical cancer. We reasoned that this routinely collected DNA could be exploited to detect somatic mutations present in rare tumor cells that accumulate in the cervix once shed from endometrial or ovarian cancers. A panel of genes that are commonly mutated in endometrial and ovarian cancers was assembled with new whole-exome sequencing data from 22 endometrial cancers and previously published data on other tumor types. We used this panel to search for mutations in 24 endometrial and 22 ovarian cancers and identified mutations in all 46 samples. With a sensitive massively parallel sequencing method, we were able to identify the same mutations in the DNA from liquid Pap smear specimens in 100% of endometrial cancers (24 of 24) and in 41% of ovarian cancers (9 of 22). Prompted by these findings, we developed a sequence-based method to query mutations in 12 genes in a single liquid Pap smear specimen without previous knowledge of the tumor's genotype. When applied to 14 samples selected from the positive cases described above, the expected tumor-specific mutations were identified. These results demonstrate that DNA from most endometrial and a fraction of ovarian cancers can be detected in a standard liquid-based Pap smear specimen obtained during routine pelvic examination. Although improvements need to be made before applying this test in a routine clinical manner, it represents a promising step toward a broadly applicable screening methodology for the early detection of gynecologic malignancies.

Clinical management of cancer patients could be improved through the development of noninvasive approaches for the detection of incipient, residual, and recurrent tumors. We describe an approach to directly identify tumor-derived chromosomal alterations through analysis of circulating cell-free DNA from cancer patients. Whole-genome analyses of DNA from the plasma of 10 colorectal and breast cancer patients and 10 healthy individuals with massively parallel sequencing identified, in all patients, structural alterations that were not present in plasma DNA from healthy subjects. Detected alterations comprised chromosomal copy number changes and rearrangements, including amplification of cancer driver genes such as ERBB2 and CDK6. The level of circulating tumor DNA in the cancer patients ranged from 1.4 to 47.9%. The sensitivity and specificity of this approach are dependent on the amount of sequence data obtained and are derived from the fact that most cancers harbor multiple chromosomal alterations, each of which is unlikely to be present in normal cells. Given that chromosomal abnormalities are present in nearly all human cancers, this approach represents a useful method for the noninvasive detection of human tumors that is not dependent on the availability of tumor biopsies.

Fundamental theories in carcinogenesis and aging evoke the accumulation of rare somatic mutations in normal tissues over time. However, absence of a simple and systematic method to characterize somatic mutations in normal tissues precludes the understanding of their functional consequences. We present Bottleneck Sequencing System (BotSeqS), a next-generation sequencing method that quantitates rare somatic point mutations simultaneously across the mitochondrial and nuclear genomes. BotSeqS combines molecular barcoding with a simple dilution step immediately before library amplification. Using BotSeqS, we determine the mutation frequencies and spectra in normal brain, kidney, and colon from a total of 34 individuals ranging from < 1 to 98 years old. We show an age and tissue-dependent accumulation of rare point mutations and demonstrate that the somatic mutational burden in normal tissues can vary by several orders of magnitude depending on biological and environmental factors. For example, individuals with defects in the mismatch repair machinery or exposure to environmental carcinogens (smoking, aristolochic acid) show significant increases in mutational frequencies and altered mutational spectra compared to controls. We further show major differences between the mutational patterns of the mitochondrial and nuclear genomes in normal tissues. Lastly, we find that the mutational spectra of normal tissues were different from each other but similar to cancers from the same tissue type, suggesting that the differential mutational spectra observed in cancers are tissue-specific rather than cancer-specific. This technology can provide insights into the number and nature of genetic alterations in normal tissues and can be used to address a variety of fundamental questions about the genomes of diseased tissues. Citation Format: Margaret L. Hoang, Isaac Kinde, Cristian Tomasetti, Thomas Rosenquist, Arthur P. Grollman, Kenneth W. Kinzler, Bert Vogelstein, Nickolas Papadopoulos. Accumulation of somatic mutations in normal and cancerous tissues with age. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr NG01.

3511Background: The conventional approach to testing the benefit of adjuvant therapies in patients (pts) with relatively favorable prognoses is to follow a large number of pts for long periods of t...

e15131Background: In pts with metastatic colorectal cancer (mCRC), the resection of isolated CLM is potentially curative. Previous studies have shown that ctDNA can be detected in a high proportion...

Massively parallel sequencing of cell-free, maternal plasma DNA was recently demonstrated to be a safe and effective screening method for fetal chromosomal aneuploidies. Here, we report an improved sequencing method achieving significantly increased throughput and decreased cost by replacing laborious sequencing library preparation steps with PCR employing a single primer pair designed to amplify a discrete subset of repeated regions. Using this approach, samples containing as little as 4% trisomy 21 DNA could be readily distinguished from euploid samples.

Clinical management of human cancer is dependent on the accurate monitoring of residual and recurrent tumors. The evaluation of patient-specific translocations in leukemias and lymphomas has revolutionized diagnostics for these diseases. We have developed a method, called personalized analysis of rearranged ends (PARE), which can identify translocations in solid tumors. Analysis of four colorectal and two breast cancers with massively parallel sequencing revealed an average of nine rearranged sequences (range, 4 to 15) per tumor. Polymerase chain reaction with primers spanning the breakpoints was able to detect mutant DNA molecules present at levels lower than 0.001% and readily identified mutated circulating DNA in patient plasma samples. This approach provides an exquisitely sensitive and broadly applicable approach for the development of personalized biomarkers to enhance the clinical management of cancer patients.

518 Background: CRC screening significantly reduces cancer incidence and mortality. Participation rates in screening, both stool based and endoscopic, are often low. The value and safety of endoscopic screening in older individuals is also uncertain. Preliminary data indicate ctDNA can be detected in a high proportion of patients with early stage CRC, suggesting promise as a screening test that should have broad community acceptance. Methods: Plasma samples were collected at diagnosis from 100 patients (pts) with newly diagnosed CRC. Surgical, clinicopathologic and outcome data were prospectively captured. All samples were sent to Johns Hopkins Kimmel Cancer Center, where tumors were sequenced using a panel of 15 genes frequently mutated in CRC to identify candidate mutations for ctDNA analysis. For each pt, one tumor mutation was selected to assess for ctDNA in plasma samples using the Safe-SeqS digital genomic assay. Results: Preliminary data is available on 68 pts. Median follow-up is 15.2 months. Candidate mutations for ctDNA analysis were identified in all cases, with a matching mutation detectable in the plasma cell-free DNA in 41 pts (60%). Median mutant allele fraction was 0.24% (range 0.11% - 8.39%). Tumor stage did not appear to have a major impact on the detection rate of ctDNA (Table), and ctDNA detection was independent of CEA levels. Five pts have recurred, all of whom had detectable ctDNA at diagnosis, whereas CEA was elevated in only 1 of these cases. Conclusions: Preliminary data suggests ctDNA is detectable at diagnosis in the majority of pts with non-metastatic CRC. The potential for ctDNA as a CRC screening tool, and as a prognostic marker for patients with early stage cancer, should be further explored. [Table: see text]

The development of minimally-invasive methods to detect and monitor tumors continues to be a major challenge in oncology. We used digital PCR-based technologies to evaluate the ability of circulating tumor DNA (ctDNA) to detect tumors in 640 patients with various cancer types. We initially use targeted, exomic, or whole genome sequencing to identify sequence or structural alterations in tumor tissues of 410 patients using targeted, exomic, or whole genome sequencing. We found that at least one tumor-specific mutant molecule could be identified in 75% of patients with advanced ovarian, colorectal, bladder, gastroesophoageal, pancreatic, breast, melanoma, hepatocellular and head and neck cancers, but in less than 50% of primary brain, renal, prostate, or thyroid cancers. In patients with localized tumors, ctDNA was detected in 73%, 57%, 48% and 50% of patients with colorectal cancer, gastroesophageal cancer, pancreatic cancer, and breast adenocarcinoma, respectively. Circulating tumor DNA was often present in patients without detectable circulating tumor cells, suggesting that these two biomarkers are distinct entities. In a separate panel of 206 patients with metastatic colorectal cancers, we showed that the sensitivity of ctDNA for detection of clinically relevant KRAS gene mutations was 87.2% while and its specificity was 99.2%. Finally, we assessed whether ctDNA could provide clues into the mechanisms underlying resistance to epidermal growth factor receptor (EGFR) blockade in 24 patients who objectively responded to therapy but who subsequently relapsed. Twenty-three (96%) of these patients developed one or more mutations in genes involved in the mitogen-activated protein kinase (MAPK) pathway. Remarkably, nearly half (45%) of the observed mutations observed were in codon 61 of either the KRAS or NRAS gene. Taken together, these data suggest that ctDNA is a broadly applicable, sensitive, specific and robust biomarker that can be used for a variety of clinical and research purposes in patients with several multiple different types of cancer. Note: This abstract was not presented at the meeting. Citation Format: Chetan Bettegowda, Mark Sausen, Rebecca Leary, Isaac Kinde, Nishant Agrawal, Bjarne Bartlett, Hao Wang, Brandon Luber, Kenneth Kinzler, Bert Vogelstein, Nickolas Papadopoulos, Luis Diaz. Detection of circulating tumor DNA in early and late stage human malignancies. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5606. doi:10.1158/1538-7445.AM2014-5606

During the assembly stage of the human immunodeficiency virus (HIV) replication cycle, several thousand copies of the viral Gag polyprotein associate at the cell membrane and bud to form an immature, non-infectious virion. Gag is subsequently cleaved by the protease, which liberates the capsid proteins for assembly into the polyprotein shell of the central core particle (or capsid) of the mature virus. Viral infectivity is critically dependent on capsid formation and stability, making the capsid protein a potentially attractive antiviral target. We have identified compounds that bind to an apical site on the N-terminal domain of the HIV-1 capsid protein and inhibit capsid assembly in vitro. One compound, N-(3-chloro-4-methylphenyl)-N'-[2-[([5-[(dimethylamino)-methyl]-2-furyl]-methyl)-sulfanyl]ethyl]urea) (CAP-1), is well tolerated in cell cultures, enabling in vivo antiviral and mechanistic studies. CAP-1 inhibits HIV-1 infectivity in a dose-dependent manner, but does not interfere with viral entry, reverse transcription, integration, proteolytic processing, or virus production, indicating a novel antiviral mechanism. Significantly, virus particles generated in the presence of CAP-1 exhibit heterogeneous sizes and abnormal core morphologies, consistent with inhibited CA-CA interactions during virus assembly and maturation. These findings lay the groundwork for the development of assembly inhibitors as a new class of therapeutic agents for the treatment of AIDS.

BACKGROUND: The development of minimally-invasive methods to detect and monitor tumors continues to be a major challenge in oncology. We used digital PCR-based technologies to evaluate the ability of circulating tumor DNA (ctDNA) to detect tumors in 640 patients with various cancer types. In particular we studied the plasma of 14 medulloblastoma, 13 WHO grade 2-3 glioma and 14 WHO grade IV astrocytoma cases for levels of ctDNA. METHODS: The basis of our approach is to differentiate DNA shed by normal cells from DNA derived from tumor cells. In order to distinguish the two populations of cell-free DNA, we first identify a tumor-specific alteration. We then query for that exact mutation in matching plasma from the same patient to generate a personalized tumor biomarker. Only DNA derived from the tumor will harbor the genetic alteration. We initially use targeted, exomic, or whole genome sequencing to identify sequence or structural alterations in tumor tissues of 410 individuals. DNA was extracted from less than 5 ml of plasma in each case. The majority of plasma samples were queried for levels of ctDNA using a high fidelity next-generation sequencing approach coined Safe-SeqS. RESULTS: We found that at least one tumor-specific mutant molecule could be identified in 75% of patients with advanced ovarian, colorectal, bladder, gastroesophoageal, pancreatic, breast, melanoma, hepatocellular and head and neck cancers, but in less than 50% of primary brain, renal, prostate, or thyroid cancers. Approximately 40% of medulloblastoma and 10% of low or high grade glioma cases had detectable levels of ctDNA. In patients with localized non-CNS tumors, ctDNA was detected in 73%, 57%, 48% and 50% of patients with colorectal cancer, gastroesophageal cancer, pancreatic cancer, and breast adenocarcinoma, respectively. Finally, we assessed whether ctDNA could provide clues into the mechanisms underlying resistance to epidermal growth factor receptor (EGFR) blockade in 24 colorectal cancer patients who objectively responded to therapy but who subsequently relapsed. Twenty-three (96%) of these patients developed one or more mutations in genes involved in the mitogen-activated protein kinase (MAPK) pathway. CONCLUSIONS: Taken together, these data suggest that ctDNA is a sensitive, specific and robust biomarker that can be used for a variety of clinical and research purposes in patients with several multiple different types of cancer. For individuals with CNS neoplasms, alternate strategies may need to be developed in order to detect cell-free tumor derived DNA at levels that are clinically meaningful. ABSTRACT CATEGORY: Neuropathology & Tumor Biomarkers.

11015 Background: Markers that better define recurrence risk for patients (pts) with stage II CC are urgently required, potentially defining a subset that would most benefit from adjuvant chemotherapy (CTX) and intensive surveillance. An alternative strategy to standard analyses of the resected surgical specimen is to directly examine plasma for evidence of residual disease. Recently, ctDNA has shown promise as a blood biomarker in advanced colorectal cancer; here we explore the potential of this marker in stage II CC. Methods: In this prospective study, plasma samples are being collected at 4-10 weeks post-op in 250 stage II CC pts, with serial 3 monthly samples on a subset of 175 pts. Adjuvant CTX is at clinician discretion, blinded to ctDNA analysis. Surveillance includes 3 monthly CEA and 6 monthly CT imaging for 2 years. All samples were sent to Johns Hopkins Kimmel Cancer Center, where tumor tissue was analyzed for hotspot mutations in TP53, APC, KRAS, NRAS, BRAF, PIK3CA, CTNNB1, SMAD4, and FBXW7 us...

11015 Background: Prognostic and predictive biomarkers in mCRC are urgently needed. Circulating tumor cells are a promising blood biomarker, but are detectable in only a minority of pts. Recently, analysis of circulating tumor DNA (ctDNA) has shown promise as a liquid biopsy, reflecting the evolving mutational status of the tumor. Here we explored baseline ctDNA as a prognostic marker, and early changes in ctDNA as a marker of CT response. Methods: Serial plasma samples and CEA were collected at baseline (D1), day 3 (D3) and cycle 2 day 1 (C2D1) from 40 mCRC pts receiving standard combination CT. Restaging scans performed at 8 weeks were centrally assessed using RECIST criteria. Samples were analyzed at Johns Hopkins Kimmel Cancer Center. Initially tumor tissue was analyzed for hotspot mutations in TP53, APC, KRAS, BRAF, PIK3CA and FBXW7. The same mutation was queried and quantified in plasma using a MPS platform (Safe-SeqS). Log-rank test was used to compare survival curves and Wilcoxon matched pairs test was used to compare paired plasma samples. Results: Preliminary data is available on 19 pts in this ongoing study. Using our initial panel at least 1 mutation was found in 16 of 19 (84.2%) tumors (7 KRAS, 3 TP53, 3 BRAF, 2 APC and 1 PIK3CA), with matching ctDNA found for each pt. For the remaining 3 cases a further panel of mutations is being analyzed. Median D1 cell free DNA (cfDNA) and ctDNA levels were 1.98 ng/ul (0.15 – 57.18) and 523 mutant fragments (frag)/ml (0.4 – 109,876), respectively. Pts with D1 cfDNA of ≥ 2.5 compared with < 2.5 had shorter median overall survival (OS; 6.9 v 12.2 months, p = 0.0086), with a trend for shorter progression-free survival (PFS; 3.6 v 8.2 months, p = 0.3477). A surge of ctDNA level from D1 to D3 was typically observed (median increase: 91.2 frag/ml, p = 0.0313), followed by a drop (median decrease from D1 to C2D1: 208.8 frag/ml, p = 0.0098). All pts with a decrease in ctDNA at C2D1 had a reduction in tumor size at 8 weeks. Conclusions: In all cases of mCRC where tumor mutation was identified, matching ctDNA was detected in plasma. Circulating DNA is a promising marker of prognosis. Early changes in DNA levels may be a useful marker of tumor response.

The development of noninvasive methods to detect and monitor tumors continues to be a major challenge in oncology. We used digital polymerase chain reaction–based technologies to evaluate the ability of circulating tumor DNA (ctDNA) to detect tumors in 640 patients with various cancer types. We found that ctDNA was detectable in >75% of patients with advanced pancreatic, ovarian, colorectal, bladder, gastroesophageal, breast, melanoma, hepatocellular, and head and neck cancers, but in less than 50% of primary brain, renal, prostate, or thyroid cancers. In patients with localized tumors, ctDNA was detected in 73, 57, 48, and 50% of patients with colorectal cancer, gastroesophageal cancer, pancreatic cancer, and breast adenocarcinoma, respectively. ctDNA was often present in patients without detectable circulating tumor cells, suggesting that these two biomarkers are distinct entities. In a separate panel of 206 patients with metastatic colorectal cancers, we showed that the sensitivity of ctDNA for detection of clinically relevant KRAS gene mutations was 87.2% and its specificity was 99.2%. Finally, we assessed whether ctDNA could provide clues into the mechanisms underlying resistance to epidermal growth factor receptor blockade in 24 patients who objectively responded to therapy but subsequently relapsed. Twenty-three (96%) of these patients developed one or more mutations in genes involved in the mitogen-activated protein kinase pathway. Together, these data suggest that ctDNA is a broadly applicable, sensitive, and specific biomarker that can be used for a variety of clinical and research purposes in patients with multiple different types of cancer.