Search

In advanced HER2-positive (HER2+) breast cancer, the new antibody-drug conjugate trastuzumab deruxtecan is more effective compared with trastuzumab emtansine (T-DM1). However, trastuzumab deruxtecan can have considerable toxicities, and the right treatment sequence is unknown. Biomarkers to guide the use of anti-HER2 therapies beyond HER2 status are needed. Here, we evaluated if preestablished levels of ERBB2 mRNA expression according to the HER2DX standardized assay are associated with response and survival following T-DM1. In ERBB2 low, medium, and high groups, the overall response rate was 0%, 29%, and 56%, respectively (P

Background: Recent evidences showed intestinal microbiota to be implicated in carcinogenesis and response to chemotherapy and immune checkpoint inhibitors in solid tumors. Furthermore, antibiotics are known to deeply influence microbiome composition in healthy people and cancer patients. The role of gut microbiome in triple negative breast cancer (TNBC) is underexplored. Methods: In this pilot prospective study, we characterized the gut microbiome of 30 TNBC patients undergoing neoadjuvant chemotherapy at two Italian Institutions. Fecal samples were collected at 2 timepoints: at the baseline (t0) and at 1 week (t1) from CT. Microbiome was analyzed by 16S rRNA sequencing. Measures of α-diversity expressed by Richness and Simpson evenness were evaluated at the species level. β-diversity was calculated using PERMANOVA test according to UniFrac measures of dissimilarity at the species level.Tumor infiltrating lymphocytes (TILs) were assessed from diagnostic core biopsy and surgical specimen. Results: From September 2017 to March 2020, 30 TNBC patients were enrolled. Median age was 53 years, 43% were premenopausal, 43% were overweight or obese (BMI>25); 97% had a histologic G3 carcinoma, clinical nodal involvements was present in 57%; median TILs at diagnosis was 30%. All patients received anthracycline and taxane-based chemotherapy, including carboplatin in 23 patients (77%). A pCR was achieved in 15 (50%) patients. The overall rate of stool samples collection was 93%. With regards to t0, no differences in terms of α- and β-diversity were found.At t1, α-diversity was significantly higher in pCR group (Simpson evenness index, p=0.016). Considering clinical-pathological features, a BMI 90 days after the end of antibiotic therapy (N=17). At this analysis, β-diversity evaluated with Unifrac measure was significantly correlated with pCR (p=0.035), with Haemophilus Influentiae being significantly enriched in non-pCR group. Conclusions: Fecal microbiome collection and analysis in this population is feasible and deserves further investigation with regards its association with response to chemotherapy. Citation Format: Grazia Maria Vernaci, Davide Massa, Ilaria Patuzzi, Alice Menichetti, Tommaso Giarratano, Gaia Griguolo, Federica Miglietta, Matteo Fassan, Edoardo Savarino, PierFranco Conte, Valentina Guarneri, Maria Vittoria Dieci. Characterization of gut microbiome composition in triple negative breast cancer patients treated with neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-12-04.

IntroductionPatients with triple-negative breast cancer (TNBC) achieving a pathological complete response (pCR) after neoadjuvant chemotherapy have a better event-free survival. The role of gut microbiome in early TNBC is underexplored.MethodsMicrobiome was analyzed by 16SrRNA sequencing.ResultsTwenty-five patients with TNBC treated with neoadjuvant anthracycline/taxane-based chemotherapy were included. Fifty-six percent achieved a pCR. Fecal samples were collected before (t0), at 1 (t1), and 8 weeks (t2) from chemotherapy. Overall, 68/75 samples (90.7%) were suitable for microbiome analysis. At t0, pCR group showed a significantly higher α-diversity as compared with no-pCR, (P = .049). The PERMANOVA test on β-diversity highlighted a significant difference in terms of BMI (P = 0.039). Among patients with available matched samples at t0 and t1, no significant variation in microbiome composition was reported over time.ConclusionsFecal microbiome analysis in early TNBC is feasible and deserves further investigation in order to unravel its complex correlation with immunity and cancer.

Background Brain metastases (BM) are common among HER2+ breast cancer (BC) and prognostic stratification is crucial for optimal management. BC-GPA score and subsequent refinements (modified-GPA, updated-GPA) recapitulate prognostic factors. Since none of these indexes includes extracranial disease control, we evaluated its prognostic value in HER2+ BCBM. Methods Patients diagnosed with HER2+ BCBM at Istituto Oncologico Veneto-Padova (2002–2021) and Montpellier Cancer Institute (2001–2015) were included as exploratory and validation cohorts, respectively. Extracranial disease control at BM diagnosis (no disease/stable disease/response vs. progressive disease) was evaluated. Results In the exploratory cohort of 113 patients (median OS 12.2 months), extracranial control (n = 65, 57.5%) was significantly associated with better OS at univariate (median OS 17.7 vs. 8.7 months, p = 0.005) and multivariate analysis after adjustment for BC-GPA (HR 0.61, 95% CI 0.39–0.94), modified-GPA (HR 0.64, 95% CI 0.42–0.98) and updated-GPA (HR 0.63, 95% CI 0.41–0.98). The prognostic impact of extracranial disease control (n = 66, 56.4%) was then confirmed in the validation cohort (n = 117) at univariate (median OS 20.2 vs. 9.1 months, p Conclusions Extracranial disease control provides independent prognostic information in HER2+ BCBM beyond commonly used prognostic scores.

Background: The incidence of breast cancer (BC) brain metastases (BM) is increasing as a result of both improved diagnostic techniques and longer survival due to better treatment approaches. However, the biological complexity of BCBMs is still poorly understood. We here evaluate the genomic profile of BCBMs and assess its prognostic implications. Methods: Clinical data and BM samples (FFPE) from BC patients undergoing neurosurgery (2003-2019) at three institutions were collected. Hormone receptor (HR) and HER2 status were evaluated on the BCBM. RNA extracted from BM samples was used to measure the expression of 758 BC–related genes and 18 housekeeping genes using the Breast Cancer 360 Panel on an nCounter platform (NanoString Technologies). Intrinsic molecular subtyping was determined using the previously reported PAM50 subtype predictor (Parker et al. JCO 2009). Median overall survival from neurosurgery (OS) was calculated using the Kaplan-Meier method. The correlations between expression of each gene/PAM50 signature, BC subtype and OS were studied using univariate and multivariate Cox-models. Results: Sixty-five BCBM samples were analyzed: 32% (N=21) were HR+/HER2-, 38% (N=25) HER2+ and 29% (N=19) HR-/HER2-. With a median follow-up of 33 months, no clinical variable was significantly associated with OS, despite a trend towards a shorter survival for patients with HR-/HER2- BMs, as compared to patients with HR+/HER2- and HER2+ subtypes (median OS 9.4 versus 22.1 and 20.0 months, respectively, log-rank p=NS). The intrinsic subtype distribution, as assessed by gene-expression profiling, was 37% Basal-like, 46% HER2-enriched (HER2-E), 15% Luminal B and 2% Normal-like. Non-luminal subtypes (basal-like and HER2-E) were extensively represented, both overall and in each BC subtype (52% in HR+/HER2- subgroup, 96% in HER2+ subgroup, see Table). The PAM50 basal-like signature was significantly associated with a worse OS (HR 2.7, 95% CI 1.0-7.2, p=0.045), even after correcting for BC subtype (HR 5.2, 95% CI 1.1-23.4, p=0.032). In fact, even within the subgroup of HR+/HER2- BCBMs, the PAM50 basal-like signature was strongly associated with a worse OS (HR 92.6, 95% CI 5.0-1860.1, p=0.003) and patients with basal-like HR+/HER2- BCBMs presented a median OS similar to patients with HR-/HER2- BCBMs (mOS 9.0 vs 9.4 months). We identified 36 genes whose high expression was significantly associated with a worse OS (p< 0.05) and one gene (LINC02381) whose high expression was significantly associated with better OS (p< 0.05); for 33 of these genes (BCL11A, BMP2, BNIP3, CAV1, CDH3, CDK6, CKB, CRYAB, CXCL12, EGFR, EYA4, FOXC1, FZD8, FZD9, GABRP, GAS1, GDF5, GPC4, IL6, KRT17, KRT5, KRT6B, KRT7, LAMB3, LINC02381, MYC, NOTCH1, PRKX, PSAT1, RUNX3, SNAI1, SPRY2, TTYH1), the association was confirmed even after correcting for BC subtype (p< 0.05). Conclusions: Non-luminal intrinsic subtypes are extensively represented in resected BCBMs, even if clinically classified as HR+/HER2-. Our data suggest that basal-like genomic features might be enriched in BCBMs and might be associated with worse survival. Distribution of PAM50 intrisic subtyping on the 65 brain metastases evaluated according to hormone receptor (HR) and HER2 status Citation Format: Gaia Griguolo, Maria Vittoria Dieci, Susan Fineberg, claudia Pinato, Michele Bottosso, Luc Bauchet, Federica Miglietta, Jack Jacob, Giovanni Zarrilli, Valérie Rigau, Maria Cristina Guarascio, Francesca Zanconato, Francesca Schiavi, Matteo Fassan, William Jacot, Stefano Piccolo, Amelie Darlix, Valentina Guarneri. Gene Expression Profiling of Breast Cancer Brain Metastasis shows enrichment for non-luminal subtypes with potential prognostic implications [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD7-08.

Pyoderma gangrenosum is a rare skin necrotizing disease that can arise on a site of surgical trauma. Its pathogenesis has recently been related to dysregulation of the immune system, with inflammatory bowel disease representing the most commonly underlying systemic conditions. Several authors have also reported an association with solid malignancies (especially gastrointestinal and breast cancer). We describe the case of a 39-year-old patient diagnosed with a locally advanced, triple-negative breast cancer who developed a pyoderma gangrenosum on the surgical wound after a CVC implant with systemic complications. As the diagnosis and management of postsurgical pyoderma gangrenosum can be challenging for clinicians, underlying conditions as autoimmune disease and solid tumors have to be considered in order to guide treatment.

Background: Hormone receptor positive (HR+)/HER2- breast cancer (BC) is a clinically and biologically heterogeneous disease, encompassing all BC molecular intrinsic subtypes. We here explore the association between gene-expression profiles and response to neoadjuvant endocrine-based treatment in early HR+/HER2- BC. Methods: The LETLOB phase II trial randomized 92 postmenopausal women with clinical stage II-IIIA HR+/HER2- BC to receive neoadjuvant letrozole + lapatinib or letrozole + placebo for 6 months. Objective response was the primary endpoint, as defined by study protocol and previously published (Guarneri, JCO 2014). Gene-expression data (Affymetrix platform) from pre-treatment frozen core-biopsies was available for 66 pts. Intrinsic subtype was assigned using a research-based PAM50 subtype predictor. The PAM50 based chemo-endocrine score (CES) was calculated using published definition (Prat, CCR 2017). Higher values of CES indicate increased endocrine sensitivity, while lower values indicate higher chemosensitivity. Results: Intrinsic subtype distribution was as follows: Luminal A 39% (N=25), Luminal B 36% (N=24), HER2-enriched 8% (N=5), basal-like 18% (N=12). Non-luminal tumors (basal-like and HER2-enriched) were characterized by less differentiated histological grades (Grade 3 65% vs 33%, p=0.037) and higher Ki67 expression at baseline as compared to luminal tumors (median 20% vs 15%, p=0.013). Considering both treatment arms combined, non-luminal tumors showed a significantly lower objective response rate as compared to luminal tumors (47% vs 78%, p=0.031). This difference was statistically significant in the lapatinib arm (43% vs 90%, p=0.021), but not in the placebo arm (50% vs 68%, p=0.449; interaction test p=0.169). After treatment, non-luminal tumors had significantly higher Ki67 levels than luminal ones (post-treatment median 10% and 7%, respectively, p=0.004). Median CES level at baseline was -0.03 (range: -1.11, +1.12). Each unit increase in CES levels at baseline was numerically associated with higher probability of achieving an objective response (Odds Ratio 1.95, 95% CI 0.74-5.18, p=0.178, both arms combined). Conclusions: In HR+/HER2- early BC patients enrolled in the LET-LOB trial, patients with non-luminal tumor or low CES score showed reduced sensitivity to endocrine-based treatment. The highest response rate (90%) was observed in luminal patients treated with letrozole + lapatinib. Gene-expression profiling could potentially be used to identify patients with low sensitivity to endocrine treatment for which neoadjuvant chemotherapy should be preferred. Citation Format: Gaia Griguolo, Maria Vittoria Dieci, Daniele Giulio Generali, Laia Paré, Antonio Frassoldati, Luigi Cavanna, Enrico Tagliafico, Katia Cagossi, Giancarlo Bisagni, Federico Piacentini, Federica Miglietta, Guido Ficarra, Aleix Prat, PierFranco Conte, Valentina Guarneri. Gene-expression profiling and response to neoadjuvant endocrine treatment in the phase II LETLOB trial [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS5-14.

Background Despite potential clinical implications, the complexity of breast cancer (BC) brain metastases (BM) immune microenvironment is poorly understood. Through multiplex immunofluorescence, we here describe the main features of BCBM immune microenvironment (density and spatial distribution) and evaluate its prognostic impact. Methods Sixty BCBM from patients undergoing neurosurgery at three institutions (2003-2018) were comprehensively assessed using two multiplex immunofluorescence panels (CD4, CD8, Granzyme B, FoxP3, CD68, pan-cytokeratin, DAPI; CD3, PD-1, PD-L1, LAG-3, TIM-3, CD163, pan-cytokeratin, DAPI). The prognostic impact of immune subpopulations and cell-to-cell spatial interactions was evaluated. Results Subtype-related differences in BCBM immune microenvironment and its prognostic impact were observed. While in HR−/HER2− BM and HER2+ BM, higher densities of intra-tumoral CD8+ lymphocytes were associated with significantly longer OS (HR 0.16 and 0.20, respectively), in HR+/HER2− BCBMs a higher CD4+FoxP3+/CD8+ cell ratio in the stroma was associated with worse OS (HR 5.4). Moreover, a higher density of intra-tumoral CD163+ M2-polarized microglia/macrophages in BCBMs was significantly associated with worse OS in HR−/HER2− and HR+/HER2− BCBMs (HR 6.56 and 4.68, respectively), but not in HER2+ BCBMs. In HER2+ BCBMs, multiplex immunofluorescence highlighted a negative prognostic role of PD-1/PD-L1 interaction: patients with a higher percentage of PD-L1+ cells spatially interacting with (within a 20 µm radius) PD-1+ cells presented a significantly worse OS (HR 4.60). Conclusions Our results highlight subtype-related differences in BCBM immune microenvironment and identify two potential therapeutic targets, M2 microglia/macrophage polarization in HER2− and PD-1/PD-L1 interaction in HER2+ BCBMs, which warrant future exploration in clinical trials.

Olaparib, an oral PARP-inhibitor, has shown clinical benefit for HER2-negative advanced breast cancer patients carrying a germinal BRCA1/2 mutation. In a randomized Phase III trial, olaparib significantly prolonged progression-free survival as compared with chemotherapy of physician choice. Moreover, in the same trial, a prespecified subgroup analysis reported an overall survival benefit for patients not previously pretreated with chemotherapy for metastatic disease. This review focuses on available preclinical, pharmacokinetic and pharmacodynamic data regarding olaparib and clinical evidence of its antitumor efficacy (both as monotherapy and in combination) and tolerability in breast cancer patients. Open questions, such as use of appropriate biomarkers for patient selection and combination/sequencing with other anticancer drugs, are also addressed.

Background: Hormone-receptor (HR)+/HER2- breast cancer (BC) is a biologically heterogeneous disease. Homologous recombination deficiency (HRD) and BRCA mutations have been previously reported to be associated with worse outcomes in HR+/HER2- metastatic BC patients receiving CDK4/6 inhibitors and endocrine therapy. Here, we assess the relation between HRD and RB-loss signatures, intrinsic subtyping, the PAM50-based chemo-endocrine score, and response to chemotherapy-based therapy and endocrine treatment in HR+/HER2- early BC. Methods: GIADA is a multicentric neoadjuvant phase II trial that treated premenopausal patients with Luminal B (LumB)-like BC (HR-positive, HER2-negative, with Ki67>20% and/or histologic Grade 3) with a combination of chemotherapy, immunotherapy and endocrine treatment. Expression of 758 genes on baseline tumor samples from all 43 patients was quantified by nCounter platform. The LETLOB phase II trial randomized postmenopausal women with clinical stage II-IIIA HR+/HER2- BC to neoadjuvant letrozole + lapatinib or letrozole + placebo for 6 months (Guarneri, JCO 2014). Gene-expression data (Affymetrix platform) from pre-treatment frozen core-biopsies was available from 66 out of 92 pts enrolled. Intrinsic subtype was assigned using a research-based PAM50 subtype predictor. A published HRD signature (Peng, Nat Commun 2014) and a signature of RB loss (RBsig), previously reported to potentially predict resistance to CDK4/6 inhibitors in HR+/HER2- BC (Malorni, Oncotarget 2016) were computed. The PAM50 based chemo-endocrine score (CES) was calculated using published definition (Prat, CCR 2017). Higher values of CES indicate increased endocrine sensitivity, while lower values indicate chemosensitivity. Association between genomic signatures was assessed through Pearson’s correlation coefficient. Association of genomic signatures with pCR was assessed through logistic regression and association with PEPI scores was assessed through Kruskal-Wallis test. Results: HRD signature levels were significantly higher in non-luminal (Basal-like and HER2-enriched) tumors as compared to Luminal (A or B) tumors (p>0.001 in the GIADA trial, p=0.021 in the LETLOB trial). Moreover, higher levels of HRD signature were associated with higher levels of RB-loss signature (Pearson correlation 0.355, p=0.020 in the GIADA trial; Pearson correlation 0.942, p< 0.001 in the LETLOB trial), higher levels of Basal-like signature (Pearson correlation 0.502, p< 0.001 in the GIADA trial; Pearson correlation 0.373, p=0.002 in the LETLOB trial) and lower levels of CES (Pearson correlation -0.422, p=0.005 in the GIADA trial; Pearson correlation -0.763, p< 0.001 in the LETLOB trial), indicative of higher chemosensitivity. In the GIADA trial, higher levels of HRD signature (p=0.018) and RBloss signature (p=0.073) and lower levels of CES (p=0.007) were associated with higher pCR rates after chemo, endocrine and immunotherapy. In the LETLOB trial, lower levels of HRD signature (p=0.068) and RBloss signature (p=0.042) and higher levels of CES (p=0.050) were associated with higher sensitivity to endocrine treatment (lower PEPI scores, 0 vs 1-3 vs 4 or more, after neoadjuvant letrozole). Conclusions: In HR+/HER2- early BC, HRD gene signatures, RB-loss gene signatures and non-luminal (especially Basal-like) intrinsic subtyping are associated with each other and associated with higher sensitivity to chemotherapy-based therapy and lower sensitivity to endocrine treatment. These observations might help correctly tailor systemic therapy, including biologic agents, in patients with HR+/HER2- early and advanced BC. Citation Format: Gaia Griguolo, Federica Miglietta, Laia Paré, Daniele G. Generali, Antonio Frassoldati, Antonino Musolino, Simon Spazzapan, Grazia Vernaci, Tommaso Giarratano, Marcello Lo Mele, Giancarlo Bisagni, Federico Piacentini, Enrico Tagliafico, Katia Cagossi, Francesca Schiavi, Claudia Pinato, Aleix Prat, Valentina Guarneri, Maria Vittoria Dieci. Homologous recombination deficiency, RB-loss gene signatures, intrinsic subtype and response to neoadjuvant treatment in HR+/HER2- early breast cancer: a correlative analysis of two phase II trials [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-02-13.

About a half of HER2-negative breast cancer (BC) show HER2-low expression that can be targeted by new antibody-drug conjugates. The main aim of this study is to describe the evolution of HER2 expression from primary BC to relapse by including HER2-low category in both primary and recurrent BC samples. Patients with matched primary and relapse BC samples were included. HER2 was evaluated according to ASCO/CAP recommendations in place at the time of diagnosis. A cutoff of10% cells staining for HER2-positivity was applied. HER2-negative cases were sub-classified as HER2-low (IHC = 1 + /2+ and ISH not amplified), or HER2-0 (IHC-0). 547 patients were included. The proportion of HER2-low cases was 34.2% on the primary tumor and 37.3% on the relapse samples. Among HER2-negative cases, HER2-low status was more frequent in HR-positive vs triple-negative tumors (47.3% vs 35.4% on primary tumor samples, 53.8% vs 36.2% on relapse samples). The overall rate of HER2 discordance was 38.0%, mostly represented by HER2-0 switching to HER2-low (15%) and HER2-low switching to HER2-0 (14%). Among patients with a primary HER2-negative tumor, the rate of HER2 discordance was higher in HR-positive/HER2-negative vs triple-negative cases (45.5% vs 36.7% p = 0.170). This difference was mostly driven by cases switching from HER2-0 to HER2-low. HER2-low expression is highly unstable during disease evolution. Relapse biopsy in case of a primary HER2-0 tumor may open new therapeutic opportunities in a relevant proportion of patients.

This article presents a comprehensive review of the current evidence related to PD‐L1 testing in breast cancer and its use as a biomarker in prediction of response to immunotherapies., In the light of recent advances in the immunotherapy field for breast cancer (BC) treatment, especially in the triple‐negative subtype, the identification of reliable biomarkers capable of improving patient selection is paramount, because only a portion of patients seem to derive benefit from this appealing treatment strategy. In this context, the role of programmed cell death ligand 1 (PD‐L1) as a potential prognostic and/or predictive biomarker has been intensively explored, with controversial results. The aim of the present review is to collect available evidence on the biological relevance and clinical utility of PD‐L1 expression in BC, with particular emphasis on technical aspects, prognostic implications, and predictive value of this promising biomarker. Implications for Practice. In the light of the promising results coming from trials of immune checkpoint inhibitors for breast cancer treatment, the potential predictive and/or prognostic role of programmed cell death ligand 1 (PD‐L1) in breast cancer has gained increasing interest. This review provides clinicians with an overview of the available clinical evidence regarding PD‐L1 as a biomarker in breast cancer, focusing on both data with a possible direct impact on clinic and methodological pitfalls that need to be addressed in order to optimize PD‐L1 implementation as a clinically useful tool for breast cancer management.

Background: Trastuzumab + pertuzumab + taxane and ado-trastuzumab emtansine (T-DM1) are standard first and second-line therapies for HER2+ metastatic breast cancer. Lapatinib is approved in combination with capecitabine in trastuzumab-resistant patients and in combination with letrozole in hormone receptor positive HER2+ pts for whom endocrine treatment is indicated. In Italy, L is also approved in combination with trastuzumab for hormone receptor-negative HER2+ pts. There are only few data on the activity of lapatinib in pts who received prior pertuzumab and /or T-DM1. Methods: We retrospectively analysed HER2+ metastatic breast cancer pts who received lapatinib after prior pertuzumab and/or T-DM1 from July 2013 to June 2018. Objective response rate (ORR) was assessed according to RECIST 1.1. Progression-free survival (PFS) was calculated from lapatinib-based therapy starting to disease progression (PD) or last follow-up. Overall Survival (OS) was calculated from lapatinib-based therapy starting to death or last follow up. Results: Data from 32 HER2+ mBC treated with lapatinib-based therapy were recorded: 30 pts (94%) received lapatinib combined with capecitabine, 1 pt received lapatinib combined with letrozole and 1 pt received lapatinib combined with trastuzumab. All patients had been treated with prior T-DM1 and 9 (28%) with prior pertuzumab for metastatic breast cancer. Setting of treatment with lapatinib-based therapy was: 2° line (n=2, 6%), 3° line (n=17, 53%) and >4° line (n=13, 41%). Patients characteristics were as follows: median age 55 years (range 35-71), hormone receptor positive 66% (n=21), stage IV at diagnosis 34% (n=11), visceral involvement at lapatinib-based therapy starting 91% (n=29). As of June 2018, lapatinib-based therapy was ongoing for 4 pts and 28 pts discontinued treatment due to disease progression (median number of courses for these pts was 8.5, range 2-27). ORR in evaluable pts was: complete response (n=1, 3%), partial response (n=13, 41%), stable disease (n=9, 28%), disease progression (n=9, 28%). Median PFS was 6.4 months (95% CI 3.0-9.8). As of June 2018, 14 pts (44%) were alive, median OS was 11.8 months (95% CI 9.9-13.6). Conclusion: These results confirm that lapatinib-based therapy retains clinical efficacy in HER2+ metastatic breast cancer pts treated with prior pertuzumab and/or T-DM1 and represents a valid therapeutic option in this setting. Citation Format: Frezzini S, Giarratano T, Dieci MV, Giorgi CA, Griguolo G, Vernaci G, Menichetti A, Mantiero M, Tasca G, Faggioni G, Falci C, Miglietta F, Mioranza E, Angelini S, Ghiotto C, Conte P, Guarneri V. Lapatinib-based therapies after pertuzumab and/or T-DM1 for HER2+ metastatic breast cancer patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-18-24.

Aim The Cher-LOB randomised phase II study showed that the combination of lapatinib-trastuzumab plus chemotherapy increases pathologic complete response (pCR) rate compared with chemotherapy plus either trastuzumab or lapatinib. Here, we report the post hoc survival analysis as per treatment arm, pCR and biomarkers. Methods The Cher-LOB study randomised 121 patients with human epidermal growth factor receptor 2–positive, stage II–IIIA breast cancer. A specific protocol to collect recurrence-free survival (RFS) and overall survival (OS) data was designed. Tumour-infiltrating lymphocytes (TILs) and PAM50-intrinsic subtyping were evaluated at baseline. Results At 9-year median follow-up, a trend towards RFS improvement with lapatinib-trastuzumab over trastuzumab was observed (hazard ratio [HR] 0.44, 95% confidence interval [CI] 0.18–1.05). Combining treatment arms, pCR was significantly associated with both RFS (HR 0.12, 95% CI 0.03–0.49) and OS (HR 0.12, 95% CI 0.03–0.49). TILs were significantly associated with RFS (HR = 0.978 for each 1% increment). Luminal-A subtype was a significant and independent predictor of improved RFS as compared with other PAM50-based intrinsic subtypes at the multivariate analysis including the most relevant clinicopathologic variables (HR 0.29, 95% CI 0.09–0.94, p = 0.040). Conclusions Cher-LOB trial survival analysis confirmed the prognostic role of pCR and TILs and showed a signal for a better outcome with lapatinib-trastuzumab over trastuzumab. Trial registration NCT00429299.

About a half of HER2-negative breast cancer (BC) show HER2-low expression that can be targeted by new antibody-drug conjugates. The main aim of this study is to describe the evolution of HER2 expression from primary BC to relapse by including HER2-low category in both primary and recurrent BC samples. Patients with matched primary and relapse BC samples were included. HER2 was evaluated according to ASCO/CAP recommendations in place at the time of diagnosis. A cutoff of >10% cells staining for HER2-positivity was applied. HER2-negative cases were sub-classified as HER2-low (IHC = 1 + /2+ and ISH not amplified), or HER2-0 (IHC-0). 547 patients were included. The proportion of HER2-low cases was 34.2% on the primary tumor and 37.3% on the relapse samples. Among HER2-negative cases, HER2-low status was more frequent in HR-positive vs triple-negative tumors (47.3% vs 35.4% on primary tumor samples, 53.8% vs 36.2% on relapse samples). The overall rate of HER2 discordance was 38.0%, mostly represented by HER2-0 switching to HER2-low (15%) and HER2-low switching to HER2-0 (14%). Among patients with a primary HER2-negative tumor, the rate of HER2 discordance was higher in HR-positive/HER2-negative vs triple-negative cases (45.5% vs 36.7% p = 0.170). This difference was mostly driven by cases switching from HER2-0 to HER2-low. HER2-low expression is highly unstable during disease evolution. Relapse biopsy in case of a primary HER2-0 tumor may open new therapeutic opportunities in a relevant proportion of patients.

Simple Summary In the last decades, tremendous advances have been made in understanding HER2-positive breast cancer biology, with a progressive improvement in survival rates of patients with this breast cancer subtype. However, a not negligible proportion of patient with HER2-positive breast cancer will eventually relapse, and metastatic HER2-positive disease is still to be considered an incurable condition, thus highlighting the imperative need to further improve our understanding in this regard. In this context, there is growing knowledge that HER2-overexpressing breast tumors are highly heterogeneous, and the co-expression of hormone-receptors may account, at least in part, for this heterogeneity. The aim of the present work is to review preclinical and clinical evidence on HER2-positive/hormone-receptor positive breast cancer, focusing on studies investigating both activity and efficacy of various combination of treatment strategies, including anti-HER2 drugs, hormonal treatments and other targeted agents, such as CDK inhibitors, both in the early and advanced setting. Abstract Enormous advances have been made in the understanding and treatment of human epidermal growth factor receptor 2-positive breast cancer (HER2+ BC) in the last 30 years that have resulted in survival gains for affected patients. A growing body of evidence suggests that hormone receptor-positive (HR+)/HER2+ BC and HR-negative (HR−)/HER2+ BC are biologically different, with complex molecular bidirectional crosstalk between the estrogen receptor and HER2 pathway potentially affecting sensitivity to both HER2-targeted and endocrine therapy in patients with HR+/HER2+ BC. Subgroup analyses from trials enrolling patients with HER2+ BC and the results of clinical trials specifically designed to evaluate therapy in patients with HR+/HER2+ BC are helping to guide treatment decisions. In this context, encouraging results with strategies aimed at delaying or reversing drug resistance, including extended adjuvant therapy and the addition of drugs targeting alternative pathways, such as cyclin-dependent kinase (CDK) 4 and 6 inhibitors, have recently emerged. We have reached the point where tailoring the treatment according to risk and biology has become the paradigm in early BC. However, further clinical trials are needed that integrate translational research principles and identify and consider specific patient subgroups and biomarkers.

Breast cancer evolves thanks to a dense and close interaction with the surrounding tumor microenvironment (TME). Fibroblasts, leukocytes, blood and lymphatic endothelial cells and extracellular matrix are the constituents of this entity, and they synergistically play a pivotal role in all of the stages of breast cancer development, from its onset to its metastatic spread. Moreover, it has been widely demonstrated that variations to the TME can correspond to prognosis variations. Breast cancer not only modulates the transformation of the environment within the mammary gland, but the same process is observed in metastases as well. In this minireview, we describe the features of TME within the primitive breast cancer, throughout its evolution and spread into the main metastatic sites.

Background In early-stage HER2-positive breast cancer, escalation or de-escalation of systemic therapy is a controversial topic. As an aid to treatment decisions, we aimed to develop a prognostic assay that integrates multiple data types for predicting survival outcome in patients with newly diagnosed HER2-positive breast cancer. Methods We derived a combined prognostic model using retrospective clinical-pathological data on stromal tumourinfiltrating lymphocytes, PAM50 subtypes, and expression of 55 genes obtained from patients who participated in the Short-HER phase 3 trial. The trial enrolled patients with newly diagnosed, node-positive, HER2-positive breast cancer or, if node negative, with at least one risk factor (ie, tumour size >2 cm, histological grade 3, lymphovascular invasion, Ki67 >20%, age

Introduction: Leptomeningeal metastasis (LM) is a severe complication of many solid tumors generally associated with dismal prognosis. Limited therapeutic options are available in this setting and assessment of response to treatment currently lacks validated tools. In 2017, the Response Assessment in Neuro-Oncology (RANO) LM Working Group proposed a standardized scorecard to aid in the evaluation of MRI findings in LM, which was revised and simplified in a subsequent 2019 version. To date, the prognostic impact of response to treatment evaluated according to these criteria has not been assessed in breast cancer (BC). In this study, we aim to validate this tool in a multicentric cohort of BC patients (pts) diagnosed with LM.Methods: Pts with LM from BC diagnosed at Istituto Oncologico Veneto (Padova, Italy) and Montpellier Regional Cancer Institute (Montpellier, France) between December 2005 and June 2018 were identified. Clinicopathological characteristics were collected from medical charts. Baseline and follow-up MRI scans were centrally reviewed by a dedicated radiologist and response assessment was evaluated according to the 2019 revised RANO LM response criteria (Le Rhun E. et al., Neuro-Oncology 2019).Results: A total of 225 pts diagnosed with BC-related LM were identified; among these, 142 had an available baseline brain MRI imaging and were included in the present study. Among these 142 pts, 78 had a positive cerebrospinal fluid (CSF) cytology and were classified as type I according to EANO-ESMO classification (41 type IA, 9 type IB, 28 type IC); for 64 pts CSF cytology was negative (N=25) or not performed (N=39), and were classified as type II (28 type IIA, 4 type IIB, 32 type IIC). At the time of last follow-up, 138 out of 142 pts had died and median overall survival (OS) from baseline MRI was 5.0 months (95% CI 3.4-6.7). Presence/absence of positive CSF cytology did not impact OS (median OS 5.3 versus 5.2 months, log-rank p=0.406). A total of 60 pts (positive/negative/not done CSF cytology: N=36/9/15) had an evaluable follow-up MRI imaging, with drop-off mainly due to deteriorating performance status or death. In this selected subgroup of pts, a longer OS was observed (median OS 15.2 months; 95% CI 9.5-21.0). Treatment administered for BC-related LM was heterogeneous and several pts received more than one treatment modality: systemic chemotherapy (N=44), endocrine therapy (N=27), HER2-targeted treatment (N=16), intrathecal chemotherapy (N=37) and radiotherapy (N=24). Response to treatment at time of first disease re-evaluation by brain MRI imaging was as follows: complete response for 2 pts, partial response for 12 pts, stable disease for 33 pts, and progression of disease for 13 pts. Response according to 2019 RANO criteria was significantly associated with OS (p=0.029, Table 1). Conclusions: Response assessment in pts with LM is challenging. In our study, the 2019 RANO revised response score was associated with OS in patients with LM from BC, thus validating these criteria in a real-world cohort. Response according to 2019 RANO LM criteriaMedian OS (months)OS 95% CI (months)Univariate Cox Hazard RatioUnivariate Cox Hazard Ratio 95% CIp-valueComplete Response31.1NE-NE0.100.01-0.780.028Partial Response16.10.0-37.40.410.17-0.970.043Stable Disease17.98.3-27.50.450.22-0.910.026Progression of Disease9.55.9-13.1Ref.Ref.Ref. Citation Format: Gaia Griguolo, Vittoria Aldegheri, Michele Bottosso, Francesca Caumo, Stéphane Pouderoux, Federica Miglietta, William Jacot, Maria Vittoria Dieci, Amélie Darlix, Valentina Guarneri. Response according to revised RANO criteria is associated with overall survival in breast cancer patients with leptomeningeal metastasis [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD4-01.

Background Breast cancer (BC) is one of the solid tumors most commonly associated with leptomeningeal disease (LMD). LMD carries a devastating prognosis; however, disease presentation and prognostic factors are uncertain. Subjects, Materials, and Methods In order to describe patient characteristics, treatment patterns, and factors associated with survival in a contemporary multicentric cohort, 153 consecutive BC patients diagnosed with LMD at two European institutions (2002–2017) were included. Time to LMD and overall survival (OS) after LMD diagnosis were evaluated using the Kaplan-Meier method and Cox proportional hazards models. Results Median age at LMD diagnosis was 58 years (25–84). Tumor phenotype distribution was as follows: hormone receptor (HR) positive (HR+)/human epidermal growth receptor 2 (HER2) negative 51.0%, triple-negative 15.0%, HR+/HER2 positive (HER2+) 13.1% and HR negative/HER2+ 7.2%. Most patients received active anticancer treatments (radiation therapy [RT] n = 42, systemic therapy n = 110, intrathecal treatment n = 103). Median OS was 3.9 months (95% confidence interval [CI] 2.4–5.5). Eastern Cooperative Oncology Group performance status (ECOG PS) >2, high white blood cells count, low glucose, and high protein in cerebrospinal fluid (CSF) were poor prognostic factors. Having received RT or systemic treatment was associated with better prognosis. In multivariate analysis, ECOG PS (hazard ratio 2.22, 95% CI 1.25–3.94), CSF glucose levels (hazard ratio 1.74, 95% CI 1.05–2.88), and having received systemic treatment (hazard ratio 0.17, 95% CI 0.09–0.32) were confirmed as independent prognostic factors. In HER2+ BC patients, having received systemic HER2-targeted therapy was the only factor maintaining independent prognostication (hazard ratio 0.12, 95% CI 0.02–0.67) in multivariate analysis. Conclusion Despite being limited by their retrospective nature, these results highlight the need for clinical trials in BC LMD, stratified on tumor biology. Implications for Practice Leptomeningeal disease (LMD) is a devastating complication of breast cancer (BC), and its optimal therapy is still not defined. Here, patient characteristics, treatment patterns, and prognostic factors from a contemporary cohort of 153 BC-related LMD patients are reported. In multivariate analysis, Eastern Cooperative Oncology Group performance status, cerebrospinal fluid glucose levels, and having received systemic treatment were confirmed as independent prognostic factors in the overall population, whereas in human epidermal growth receptor 2 (HER2) positive BC patients, having received systemic HER2-targeted therapy was the only factor maintaining independent prognostication in multivariate analysis. These results highlight the need to consider stratification on tumor biology in the treatment of BC LMD.

Background: Among solid tumors, breast cancer (BC) is one of the most common cause of leptomeningeal metastases. Leptomeningeal disease (LMD) typically carries a devastating prognosis; however, disease presentation and prognostic factors are still uncertain. The aim of this study was to characterize clinical features of LMD in relation to BC histology and subtypes. Patients and Methods:104 patients (pts) with LMD from BC diagnosed between 2002 and 2017 at two European institutions were included. LMD diagnosis was based on the presence of neoplastic cells on cerebrospinal fluid examination and/or radiological evidence of LMD. Patients' characteristics and their associations with time from LMD to death or last follow up were evaluated by the Kaplan-Meier method, log-rank tests, and Cox proportional hazard models. Results: Median age at LMD diagnosis was 56 yrs (range 26-75). Tumor histology (n=102) was ductal in 72 pts (70.6%), lobular in 22 (21.6%) and other histology in 8 (7.8%, including mixed ductal and lobular tumors). Tumor phenotype distribution was as follows: hormone receptor (HR)+/HER2- 54.8%, triple-negative (TN) 14.4%, HR+/HER2+ 12.5%, HR-/HER2+ 6.7% and unknown 11.5%. LMD diagnosis was cytologically proven (n=64, 62.7%) and/or radiologically proven (n=88, 85.4%). At time of LMD diagnosis, 63 pts (58.9%) had an ECOG performance status (PS) ≤ 2. 91 pts (87.5%) had extra-CNS disease localizations and 20 (18.7%) had a history of known BC brain metastasis (BM) (predating LMD diagnosis of more than 30 days). In lobular BC, LMD diagnosis was more frequently made in the absence of a known history of BM compared with ductal BC (95.5% vs 73.3%, Fisher test p=0.036). A majority of pts was treated with intrathecal (n=59, 55.1%) or systemic treatment (n=73, 68.2%) after LMD diagnosis, while only a minority underwent radiotherapy (n=28, 26.2%) or surgical derivation procedures (n=14, 13%). Median overall survival (OS) from LMD diagnosis was 3.2 months (95% CI, 1.9-4.4 months). No significant difference was observed across tumor phenotypes, with HER2+ subgroups experiencing better outcomes (median OS: 2.9, 1.6, 6.6 and 12.9 months in HR+HER2-, TN, HR+HER2+ and HR-HER2+ subgroups; p=0.54). In univariate analysis, ECOG PS ≤ 2 at LMD diagnosis, intrathecal treatment and systemic treatment after LDM diagnosis were significantly associated with an improved OS (see table). Multivariate analysis showed that only ECOG PS ≤ 2 and systemic treatment after LMD diagnosis were independent factors associated with OS (see table). Updated results on an extended cohort of about 150 patients total will be presented at the meeting. UnivariateMultivariatePrognostic factorsMedian OS in months (95%CI)HR (95%CI)pHR (95%CI)pECOG PS 0-25.9 (2.1-9.7)0.43 (0.27-0.66)0.0010.64 (0.4-1.0)0.06≥31.7 (1.2-2.3)ref ref Intrathecal treatment Yes5.3 (1.9-8.7)0.65 (0.43-0.98)0.0370.89 (0.57-1.38)0.6No1.9 (0.5-3.3)ref ref Systemic treatment Yes7.3 (4.7-9.8)0.13 (0.08-0.22) Conclusions: LMD carries a dismal prognosis. The results of this series highlight that patient-related features and treatments (in particular the use of systemic treatment) contribute to modulate the prognosis of BC pts with LMD. Citation Format: Griguolo G, Pouderoux S, Dieci MV, Jacot W, Bourgier C, Miglietta F, Firmin N, Conte P, Viala M, Guarneri V, Darlix A. Clinical presentation and outcome of leptomeningeal metastasis in patients with breast cancer in relation to histology and tumor subtypes [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-17-04.

International audience; BACKGROUND:Several prognostic scores have been developed to estimate survival of breast cancer (BC) patients with brain metastases (BM). Modified Breast Graded Prognostic Assessment (GPA), based on a single-institution cohort of 1552 patients, has been proposed as refinement of Breast-GPA. In addition to age, tumour subtype and KPS, Modified Breast-GPA comprises number of BM. This study was designed to validate Modified Breast-GPA.PATIENTS AND METHODS:Clinical data of 668 BC patients diagnosed with BM at four institutions between 1996 and 2016 were reviewed. Patients were classified by Breast-GPA and Modified Breast-GPA. Overall survival (OS) was calculated from time of BM diagnosis to death or last follow-up. Cox proportional models were used to calculate hazard-ratios and their 95% CI. The performances of Breast-GPA and Modified Breast-GPA were compared using Harrell's concordance index.RESULTS:Median age at BM diagnosis was 56 years (range 24-85). At last follow-up, 632 patients (94.6%) had died. Median OS was 8.1 months (95% CI 6.9-9.4). The number of BM (1-3 vs. >3) was significantly associated with OS in univariate analysis (p < 0.001) and having >3 BM was identified as a negative prognostic factor in multivariate analysis. Both Breast-GPA and Modified Breast-GPA accurately predicted OS (p < 0.001 for both scores). Performance of Modified Breast-GPA was better: concordance indices were 0.6390 (95% CI, 0.6381 to 0.6399) and 0.6647 (95% CI, 0.6639 to 0.6655) for Breast-GPA and Modified Breast-GPA, respectively (p < 0.001).CONCLUSIONS:This work provides the first external independent validation of Modified Breast-GPA and confirms its better performance as compared to Breast-GPA.

Background: Brain metastases (BM) are a serious relatively common complication of breast cancer (BC). We evaluated prognostic factors for survival after diagnosis of BM from BC in a contemporary cohort of pts. Methods:Pts diagnosed with BM from BC between 1999 and march 2016 and treated at the Istituto Oncologico Veneto of Padua were evaluated. Overall survival (OS) was defined as time from BM diagnosis to death or last follow-up. Pts were classified in 4 categories according to the breast cancer-specific Graded Prognostic Assessment (GPA) index according to validated criteria (Sperduto et al, 2012), based on age, Karnofsky Performance Status (KPS) and BC phenotype. Cox proportional models were used to calculate HR and 95% CI. Results: 199 pts were identified. Median age at BM diagnosis was 56 yrs (range 28-84). Tumor phenotype distribution was as follows: triple negative (TN, 20.1%), hormone receptor (HR)-HER2+ (16.8%), HR+HER2+ (24.0%) and HR+HER2- (39.1%). Median time to BM diagnosis was 48.9 months (range 0-327), with significant differences according to tumor phenotype (median 27.3, 31.8, 46.1 and 55.2 months in TN, HR-HER2+, HR+HER2+, HR+HER2-, respectively, p=0.009). With respect to OS, no significant difference was observed across tumor phenotypes, with TN patients experiencing the worse outcome (median: 4.7, 7.7, 11.0 and 6.2 months in TN, HR-HER2+, HR+HER2+, HR+HER2-, p=0.187). The breast-specific GPA index, which combines tumor phenotype with patient-related features, was significantly associated with OS (Table). The number of local treatment received (radiotherapy, either whole brain or stereotactic, or neurosurgery) and the administration of systemic treatment after BM diagnosis were significantly associated with better OS (Table). Patients in the less favorable GPA category (GPA index Prognostic factorsMedian OS, months (95%CI)HR (95%CI), univariatep, univariateHR (95%CI), corrected for GPAGPA category 3.5-418.8 (15.2-22.5)ref -2.5-38.8 (3.8-13.8)1.40 (0.80-2.43) -1.5-25.5 (3.5-7.5)1.76 (1.00-3.10) -0-1.02.7 (1.2-4.3)2.67 (1.35-5.28)0.019-Number of local tretaments received 03.0 (1.8-7.5)ref ref18.0 (5.8-10.3)0.53 (0.38-0.74) 0.54 (0.38-0.78)221.3 (15.2-27.3)0.36 (0.20-0.65) 0.49 (0.26-0.93)335.5 (33.5-37.6)0.12 (0.04-0.38) Conclusions: Patient-related features, tumor phenotype and multimodal treatments all independently contribute to modulate the prognosis of pts with BM from BC. Citation Format: Griguolo G, Dieci MV, Giarratano T, Giorgi CA, Orvieto E, Ghiotto C, Falci C, Mioranza E, Tasca G, Milite N, Miglietta F, Conte P, Guarneri V. Factors related to the prognosis of breast cancer patients after the development of brain metastases [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-12-06.

Background: Tumor infiltrating lymphocytes (TILs) have emerged as a prognostic and potential predictive factor in early triple negative (TN) and HER2+ breast cancer (BC). The prognostic role of TILs in advanced disease is largely unknown. Methods: 109 HER2+ and TNBC patients with available tumor tissue from regional/distant BC recurrence (collected between 2001 and 2015) were identified from a prospectively maintained database at the Istituto Oncologico Veneto of Padova (Italy). Ipsilateral in-breast relapse/second primaries and contralateral BC were excluded from the definition of recurrence. StrTILs were assessed according to consensus guidelines (Salgado, 2014) on hematoxylin and eosin stained slides from BC recurrence samples and, when available, matched primaries. Post-progression survival was calculated as the time from first BC recurrence to last follow up or death. Results: StrTILs were evaluable on recurrent BC for 72 cases (HER2+ n=43, TN n=29), after exclusion of lymphnode metastases. Median time to recurrence from initial BC diagnosis was longer for HER2+ than TN cases: 37 months (95%CI 23-51) and 18 months (95%CI 13-23), respectively. Accordingly, median time to biopsy of recurrence from initial BC diagnosis was 43 months (95%CI 35-51) for HER2+ patients and 20 months (95%CI 9-31) for TN patients. Site of biopsy was visceral metastasis in 54% and soft tissue metastasis in 46% of cases (similar for HER2+ and TN). Median StrTILs level on recurrence was 5% (Q1 2,5%, Q3 10%), without differences according to TN or HER2+ phenotype (Student's t-test p=0.5). In the whole cohort, post-progression survival did not differ for patients with high (>10%) vs low ( In the TN subgroup, high StrTILs on recurrence were associated to a better post-progression survival (median not reached vs 12.7 months for StrTILs >10% and StrTILs were assessed on matched primary tumors for 43 patients. Overall, no significant StrTILs variation between primary tumor and recurrence was observed (mean change -4.5%, Wilcoxon p=0.5). Mean change was -2.5% and -7% in HER2+ and TN cases (Wilcoxon p=0.63 and p=0.15, respectively). For TN patients with StrTILs Conclusions: Levels of StrTILs on recurrent BC seem to have an opposite effect on prognosis of metastatic BC patients according to tumor phenotype. Immunohistochemical characterization of TILs is ongoing, data will be available for the meeting. Citation Format: Dieci MV, Giaratano T, Miglietta F, Griguolo G, Orvieto E, Falci C, Giorgi CA, Mioranza E, Tasca G, Cappellesso R, Ghiotto C, Conte P, Guarneri V. Tumor infiltrating lymphocytes in recurrent HER2+ and triple negative breast cancer: Prognostic value according to tumor phenotype [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-05-20.

Background: The integration of Residual Cancer Burden (RCB) and post-treatment Ki67 (Residual Proliferative Cancer Burden [RPCB] index) has been proposed as a stronger predictor of long-term outcome in unselected breast cancer (BC) patients undergoing neoadjuvant chemotherapy (NACT), as compared to RCB. However, no specific analysis in the subgroup of patients with hormone-receptor (HR)-positive/HER2-negative BC is available so far. We investigated the prognostic value of RPCB in an independent cohort of hormone-receptor (HR) positive/HER2 negative BC patients treated with NACT at our Institution. Methods: A cohort of 130 stage II-III, HR+/HER2 negative BC patients who underwent NACT between 2000 and 2014 was included. Archival surgical specimens were evaluated for RCB (Symmans et al. J Clin Oncol 2007). RPCB was calculated by combining RCB and Ki67 as previously described (Sheri et al, Ann Oncol 2015). Patients were categorized in 4 RCB categories (pathological complete response -pCR- and RCB tertiles) and 4 RPCB categories (pCR and RPCB tertiles). Disease-free Survival (DFS) and overall Survival (OS) estimates were determined by Kaplan-Meier analysis and compared using the log-rank test. The c-index was used to compare the performance of the prognostic models. Results: Patients characteristics were: ductal histology 70%, Grade 3 41%, Stage III 54%, PgR negative (≤10%) 35%, median Ki67 at diagnosis 25%. Neoadjuvant chemotherapy included both anthracycline and taxane in 92% of cases. The rate of pCR was 8%. The vast majority of patients received adjuvant endocrine therapy (96%), whereas 30% received further adjuvant chemotherapy. Median follow up was 8.5 years (95% CI 8.0-9.0). RCB was calculated for 105 patients and RPCB was calculated for 85 patients. RPCB was better than RCB in predicting both DFS and OS (5-year DFS and 8-year OS according to RPCB and RCB are reported in the Table). The c-index for DFS prediction was numerically higher for RPCB vs RCB (0.4042316 vs 0.3396437, p=0.08). Similar results were observed for OS prediction: c-index 0.3099490 (RPCB) vs 0.2372449 (RCB), p=0.08. Conclusions: This is the first study evaluating RPCB specifically in HR+/HER2- BC patients treated with NACT. In this independent cohort, after a median follow up of 8.5 years, RPCB was a strong predictor of DFS and OS. The better performance of RPCB vs RCB was in part due to the ability of RPCB to discriminate a subgroup of patients with a particularly worse prognosis after NACT, who may be candidate for clinical trials evaluating novel adjuvant treatments. Five-year DFS and eight-year OS according to RPCB and RCB5-year DFSp-value8-year OSp-valueRPCBpCR100%0.041100% Citation Format: Federica Miglietta, Vassilena Tsvetkova, Maria Vittoria Dieci, Gaia Griguolo, Grazia Vernaci, Alice Menichetti, Cristina Falci, Giovanni Faggioni, Tommaso Giarratano, Simona Frezzini, Eleonora Mioranza, Marcello Lo Mele, PierFranco Conte, Valentina Guarneri. Validation of residual proliferative cancer burden (RPCB) as a predictor of long-term outcome following neoadjuvant chemotherapy in hormone-receptor positive/HER2 negative breast cancer patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-06-12.