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e20628 Background: Hyperprogressive disease (HPD) incidence ranges from 8% to 21% in patients treated with anti-PD-1/PD-L1 mAbs in NSCLC and is associated with poor survival. Previously published data underlined a link between HPD across different cancers types and specific genetic alterations, such as MDM2 amplification and EGFR aberrations. We present a single-center cohort of patients with NSCLC and PD-L1 > 50% treated with 1st-line pembrolizumab. We performed NGS, IHC and FISH analysis to evaluate genetic correlations with the clinical phenotype. Methods: Clinical data from 20 patients with diagnosis of advanced NSCLC treated with 1stline immunotherapy pembrolizumab were retrospectively collected. HPD was defined by Time to Treatment Failure ≤2 months and raising in Tumor Burden ≥50% compared with basal CT-scan. MDM2 amplification was investigated by FISH on FFPE tissue sections using the MDM2/CON12 break apart FISH Probe. Positive cases were defined as those with > 10% positive tumor cells. We performed IHC for MDM2 protein on FFPE tissue sections. The staining was semiquantitatively graded for the intensity as: 0, negative; 1+, weak positive; 2+, moderately positive; 3+, strongly positive, and for the extent as 0– < 1% (negative), 1–50% (focal), and > 50% (diffuse). We also performed NGS analysis (FoundationOne CDX, Foundation Medicine Inc.) on 324 preidentified genes. Results: We identified 5 cases of HPD; all five cases showed MDM2amplification by FISH analysis and a focal protein expression by IHC with the strongest nuclear staining observed in the cases showing a higher degree of MDM2 amplification (8/9 dots) and a weaker expression in those with a lower MDM2amplification (4/5 dots). NGS analysis showed MDM2amplification in 1/5 HPD patient and a loss of CDKN2A/B in 4/5 patients. None of the non-HPD patients had IHC expression of MDM2 or amplification of the gene. Among the non-HPD patients no genetic alterations regarding MDM2 and/or CDKN2A/B were found on NGS analysis. Conclusions: Our data suggest a potential role of CDKN2A/B gene loss and alteration of MDM2 on the establishment of HPD in NSCLC patients treated with immunotherapy. Because the HPD logic is not yet clear, more data is needed to better understand the link between this genomic signature and the development of HPD.

700 Background: The standard of care for locally advanced rectal cancer (RC) is neoadjuvant chemoradiotherapy (CRT) with 5FU aimed to tumor downstaging prior to radical resection but there is a wide spectrum of responses to it, from none to complete. The aim of this project is to validate top candidate genes previously identified by microarray studies as prognostic and predictive classifiers of locally advanced RC, using the NanoString nCounter Platform. Methods: Two cohorts of RC patients were identified according to tumor regression grade (TRG) of AJCC Staging Manual (7th) system: 1) good prognosis: patients that after neoadjuvant CRT obtained TRG0 (complete response); 2) poor prognosis: patients with TRG1 (moderate response), patients with TRG2 (minimum response rate) and patients with TRG3 (poor response). Pre-treatment biopsies tissues from ten TRG0 patients (ID TRG0bio) and thirteen TRG1-3 patients (ID TRG1-3bio) were macro-dissected from FFPE sections, RNA isolated and used for expression profiling of a 305 genes custom code set consisting of 12 normalizer genes, 101 prognostic genes (markers of stemness, invasiveness, proliferation, drug-resistance), 192 predictive genes (involved in response to 5-FU, to radiation therapy and in the response to CRT). All samples were normalized using the geometric mean of the housekeeper genes. P-values were calculated by student’s t-test and was consider significance if was less than 0.05. Gene-specific RNA expression profiles were compared using Spearman's correlation. The heat map was generated using MeV 4.9.0. Results: When we compared TRG0bio to TRG1-3bio tissues, among the 305 genes assayed, changes in expression levels of 18 genes (SSB, GAPDH, TXNDC9, DUT, PKM, STAT1,SLC28A3, DAG1, TYMS, FERMT1, ARNT,SLC6A6, SMAD3, SCRN1, POU5F1, GNG4, PDRG1, ATP5E) were statistically significant. Conclusions: Results suggest that TRG0 RC is characterized by distinct molecular events compared TRG1-3 disease. Next steps will be: to amplify sample size, to understand signaling pathways of top differentially expressed genes and to validate prospectively our gene signature.

e14042 Background: The KRAS aKtive program was started on March 2009, promoted by the Italian Association of Medical Oncology (AIOM) and the Italian Society of Surgical Pathology and Cytopathologyy (SIAPEC) to support the activity of oncologists and pathologists involved in the management of metastatic colorectal cancer patients who need the assessment of the mutational status of the KRAS gene. Methods: The program was specifically devised to facilitate the exchange of biologic material, clinicopathological data and diagnostic reports within a network of oncologist, pathologists and pathology/molecular biology reference laboratories throughout Italy, connected through the site www.kras-aKtive.it. KRAS mutation analysis was performed by Sanger sequencing (SS), real time PCR or other techniques, including pyrosequencing and hybridization strip assays. Data were collected in a common database. Results: The KRAS aKtive program has involved 478 oncologists, 144 pathologists, and 24 reference laboratories. A total of 7,432 KRAS mutations analyses were performed. The tests were informative in 7,265 cases (98%). The vast majority of tests (5,626 cases, 77.4%) were conducted by SS. In 529 (7.3%) cases a real-time PCR assay was used, other detection techniques were used in 1,110 (15.3%) cases. KRAS mutations at codons 12-13 were detected in 2,874 cases (39,6%). The frequency of mutations detected by real-time PCR or other techniques (45%, and 43%, respectively) was significantly higher (p=0.002, and p=0.008%, respectively) than that observed by SS (38%). The percentage of cases evaluated by non-SS-based methods has increased during the first three years of the program. Conclusions: The results of this large survey allow an accurate estimation of the actual prevalence of KRAS mutations and their types in caucasian colorectal cancer patients. Our data indicate that the frequency of mutations detected by non-SS-based methods is higher than that obtained by SS.

e14000 Background: The Italian Association of Medical Oncology (AIOM) and the Italian Society of Surgical Pathology and Cytopathologyy (SIAPEC) collaborated to promote a national program (KRAS aKtive) to support the activity of oncologists and pathologists involved in the management of metastatic colorectal cancer patients who need the assessment of the mutational status of the KRAS gene. Methods: The KRAS aKtive program was specifically devised to facilitate the exchange of biologic material, clinicopathological data and diagnostic reports within a network of oncologist, pathologists and pathology/molecular biology reference laboratories throughout Italy, connected through the site www.kras-aKtive.it. KRAS mutation analysis was performed by PCR-Sanger sequencing, real time PCR or other techniques. Data were collected in a common database. Results: Started on March 2009, the KRAS aKtive program has involved 407 oncologists, 125 pathologists, and 24 reference laboratories from 16 of the 21 Italian regions....