Tumor Genotyping and Homologous Recombination Repair Gene Variants in Patients With Epithelial Ovarian Cancer: Is Pathogenic Enough?

Our hypothesis was that the predictive accuracy of pathogenic variants in genes participating in the homologous recombination repair (HRR) system in patients with epithelial ovarian cancer (EOC) could be improved by considering additional next-generation sequencing (NGS) metrics. NGS genotyping was performed in tumor tissue, retrospectively and prospectively collected from patients with EOC, diagnosed from 8/1998 to 10/2016. Variants were considered clonal when variant allele frequencies corresponded to >25%. The primary endpoint was overall survival (OS). This study included 501 patients with EOC, predominantly with high-grade serous (75.2%) and advanced stage tumors (81.7%); median age was 58 years (22-84). Pathogenic and clonal pathogenic variants in HRR and/or TP53 genes were identified in 72.8% and 66.5% tumors, respectively. With a median follow-up of 123.9 months, the presence of either pathogenic or clonal pathogenic HRR-only variants was associated with longer OS compared to HRR/TP53 co-mutation (HR=0.54; 95% CI, 0.34-0.87, Wald's p=0.012 and HR=0.45; 95% CI, 0.27-0.78, Wald's p=0.004, respectively). However, only the presence of clonal HRR-only variants was independently associated with improved OS (HR=0.55; 95% CI, 0.32-0.94, p=0.030). Variant clonality and co-occuring TP53 variants affect the predictive value of HRR pathogenic variants for platinum agents in patients with EOC.

Clinical Trial Registration

[ClinicalTrials.gov], identifier [NCT04716374].

Clinical Significance of Germline Cancer Predisposing Variants in Unselected Patients with Pancreatic Adenocarcinoma

Our aim was to determine the prevalence, prognostic and predictive role of germline pathogenic/likely pathogenic variants (P/LPVs) in cancer predisposing genes in patients with pancreatic ductal adenocarcinoma (PDAC). Germline testing of 62 cancer susceptibility genes was performed on unselected patients diagnosed from 02/2003 to 01/2020 with PDAC, treated at Hellenic Cooperative Oncology Group (HeCOG)-affiliated Centers. The main endpoints were prevalence of P/LPVs and overall survival (OS). P/LPVs in PDAC-associated and homologous recombination repair (HRR) genes were identified in 22 (4.0%) and 42 (7.7%) of 549 patients, respectively. P/LPVs were identified in 16 genes, including ATM (11, 2.0%) and BRCA2 (6, 1.1%), while 19 patients (3.5%) were heterozygotes for MUTYH P/LPVs and 9 (1.6%) carried the low-risk allele, CHEK2 p.(Ile157Thr). Patients carrying P/LPVs had improved OS compared to non-carriers (22.6 vs. 13.9 months, p = 0.006). In multivariate analysis, there was a trend for improved OS in P/LPV carriers (p = 0.063). The interaction term between platinum exposure and mutational status of HRR genes was not significant (p-value = 0.35). A significant proportion of patients with PDAC carries clinically relevant germline P/LPVs, irrespectively of age, family history or disease stage. The predictive role of these P/LPVs has yet to be defined. ClinicalTrials.gov Identifier: NCT03982446.

Transcriptomics and solid tumors: The next frontier in precision cancer medicine

Transcriptomics, which encompasses assessments of alternative splicing and alternative polyadenylation, identification of fusion transcripts, explorations of noncoding RNAs, transcript annotation, and discovery of novel transcripts, is a valuable tool for understanding cancer mechanisms and identifying biomarkers. Recent advances in high-throughput technologies have enabled large-scale gene expression profiling. Importantly, RNA expression profiling of tumor tissue has been successfully used to determine clinically actionable molecular alterations. The WINTHER precision medicine clinical trial was the first prospective trial in diverse solid malignancies that assessed both genomics and transcriptomics to match treatments to specific molecular alterations. The use of transcriptome analysis in WINTHER and other trials increased the number of targetable -omic changes compared to genomic profiling alone. Other applications of transcriptomics involve the evaluation of tumor and circulating noncoding RNAs as predictive and prognostic biomarkers, the improvement of risk stratification by the use of prognostic and predictive multigene assays, the identification of fusion transcripts that drive tumors, and an improved understanding of the impact of DNA changes as some genomic alterations are silenced at the RNA level. Finally, RNA sequencing and gene expression analysis have been incorporated into clinical trials to identify markers predicting response to immunotherapy. Many issues regarding the complexity of the analysis, its reproducibility and variability, and the interpretation of the results still need to be addressed. The integration of transcriptomics with genomics, proteomics, epigenetics, and tumor immune profiling will improve biomarker discovery and our understanding of disease mechanisms and, thereby, accelerate the implementation of precision oncology.

Review of precision cancer medicine: Evolution of the treatment paradigm

In recent years, biotechnological breakthroughs have led to identification of complex and unique biologic features associated with carcinogenesis. Tumor and cell-free DNA profiling, immune markers, and proteomic and RNA analyses are used to identify these characteristics for optimization of anticancer therapy in individual patients. Consequently, clinical trials have evolved, shifting from tumor type-centered to gene-directed, histology-agnostic, with innovative adaptive design tailored to biomarker profiling with the goal to improve treatment outcomes. A plethora of precision medicine trials have been conducted. The majority of these trials demonstrated that matched therapy is associated with superior outcomes compared to non-matched therapy across tumor types and in specific cancers. To improve the implementation of precision medicine, this approach should be used early in the course of the disease, and patients should have complete tumor profiling and access to effective matched therapy. To overcome the complexity of tumor biology, clinical trials with combinations of gene-targeted therapy with immune-targeted approaches (e.g., checkpoint blockade, personalized vaccines and/or chimeric antigen receptor T-cells), hormonal therapy, chemotherapy and/or novel agents should be considered. These studies should target dynamic changes in tumor biologic abnormalities, eliminating minimal residual disease, and eradicating significant subclones that confer resistance to treatment. Mining and expansion of real-world data, facilitated by the use of advanced computer data processing capabilities, may contribute to validation of information to predict new applications for medicines. In this review, we summarize the clinical trials and discuss challenges and opportunities to accelerate the implementation of precision oncology.

Oncologist Burnout Syndrome in Eastern Europe: Results of the Multinational Survey

PURPOSE

Burnout is defined as a three-dimensional syndrome-emotional exhaustion (EE), depersonalization (DP), and reduced personal accomplishment (PA)-caused by chronic occupational stress. The aim of the current study was to investigate the prevalence of burnout among oncologists in Eastern Europe and to identify the contributing factors.

METHODS

The study was conducted as an online survey between October 2017 and March 2018. Oncologists (including medical, radiation, clinical, and surgical oncologists) from 19 countries were invited to participate. The survey consisted of 30 questions, including the standardized burnout instrument, Maslach Burnout Inventory, and eight demographic questions. Burnout risk was scored according to the scoring manual for health care workers.

RESULTS

The study included 637 oncologists. Overall, 28% were at low or intermediate risk and 72% were at high risk for burnout. Forty-four percent of participants were at high risk for EE, 28.7% for DP, and 47.3% for PA. EE risk was associated with female sex. DP risk was highest among clinical and radiation oncologists, whereas PA risk was positively correlated with years of service, percentage of cancer deaths, and availability of the number of oncologists. In multivariate logistic regression analysis, burnout was significantly associated with standardized cancer mortality and fewer years of practice.

CONCLUSION

Burnout among oncologists in Eastern Europe is high, and younger oncologists are the most vulnerable group. Preventive measures should be taken to address this issue, which negatively affects optimal care delivery and poses a threat to oncologists' health and well-being.

Pathogenic mutations and overall survival in 3,084 patients with cancer: the Hellenic Cooperative Oncology Group Precision Medicine Initiative

Background: We evaluated the association between pathogenic mutations and overall survival (OS) in patients with cancer referred to Hellenic Cooperative Oncology Group–affiliated Departments.

Patients and methods: Patients referred from 12/1980 to 1/2017 had molecular testing (for research) of archival tumor tissue collected at the time of first diagnosis (non-metastatic, 81%; metastatic, 19%). Tumor-specific gene panels (16-101 genes) were used to identify pathogenic mutations in clinically relevant genes. NGS genotyping was performed at the Laboratory of Molecular Oncology, Aristotle University of Thessaloniki. Annotation of mutations was performed at MD Anderson Cancer Center.

Results: We analyzed 3,084 patients (median age, 57 years; men, 22%) with sequencing data. Overall, 1,775 (58% of 3,084) patients had pathogenic mutations. The median follow-up was 7.52 years (95% CI, 7.39-7.61). In patients with non-metastatic tumors, after stratification by tumor type, increasing age, higher grade, and histology other than adenocarcinoma were associated with shorter OS. OS was also shorter in patients with pathogenic TP53 (HR=1.36; p<0.001), MLL3 (HR=1.64; p=0.005), and BRCA1 (HR=1.46; p=0.047) mutations compared to wild-type genes. In multivariate analyses, independent prognostic factors predicting shorter OS were pathogenic mutations in TP53 (HR=1.37, p=0.002) and MLL3 (HR=1.50, p=0.027); increasing age (HR=1.02, p<0.001); and increasing grade (HR=1.46, p<0.001). In patients with metastatic cancer, older age and higher grade were associated with shorter OS and maintained their independent prognostic significance (increasing age, HR=1.03, p<0.001 and higher grade, HR=1.73, p<0.001).

Conclusions: Analysis of molecular data reveals prognostic biomarkers, regardless of tissue or organ of origin to improve patient management.

Pathology of BRCA1- and BRCA2-associated Breast Cancers: Known and Less Known Connections

INTRODUCTION

BRCA1/BRCA2 mutation carriers indefinitely comprise a distinct group of patients with breast cancer (BC), with their tumors displaying specific pathologic characteristics. Although these connections are known, they are not fully elucidated. We therefore sought to investigate the clinicopathologic characteristics and overall survival of Greek patients with BC carrying BRCA1/BRCA2 mutations.

PATIENTS AND METHODS

Greek patients with BC diagnosed between 1999 and 2016, fulfilling the National Comprehensive Cancer Network criteria for genetic testing, were analyzed for BRCA1/BRCA2 mutations by Sanger sequencing or by a 94-gene panel. Medical records and pathology reports were retrospectively reviewed to retrieve patient and tumor baseline characteristics. Potential associations with mutation status were assessed using the Fisher exact, Pearson χ², and Mann-Whitney tests.

RESULTS

Of 2096 selected patients with BC, we identified 297 (14.2%) BRCA1 and 88 (4.2%) BRCA2 carriers. The mean age at BC diagnosis was 40 and 42.6 years, respectively (P = .02). Tumor histologic subtypes in BRCA1 and BRCA2 carriers were predominantly ductal (79%) followed by medullary (10%), and ductal (72%) followed by lobular (15%), respectively. A significantly higher percentage of BRCA2 tumors were human epidermal growth factor receptor 2-positive, compared with BRCA1 tumors (21.7% vs. 5.8%; P < .001). Second primary cancer diagnosis was more frequent in BRCA1 compared with BRCA2 mutation carriers (36.2% vs. 10.7%; P < .001), whereas there was no difference in 15-year overall survival (hazard ratio, 0.92; 95% confidence interval, 0.48-1.83; P = .804) between the 2 groups.

CONCLUSIONS

These data confirm established observations in the pathology of BRCA-related tumors and provide further insight on the association of rare histologic entities with mutations in these genes, which can be clinically beneficial.

Abstract 486: Pathogenic drivers and their comutations in genes frequently altered in cancer

Background - aim: The as yet publicized results from Precision Oncology trials highlight the need to define parameters that may interfere with the actionability of common pathogenic drivers. One such parameter may be the presence of multiple drivers within the same tumor. Here, we investigated the properties of single and coexisting pathogenic mutations in genes frequently altered and targeted across cancers.

Methods: We examined informative deep sequencing data for TP53, PIK3CA, KRAS and BRCA1 from 2672 paraffin tumors that were obtained at first diagnosis (88% stage I-III; 12% stage IV) from patients with breast (n=1745), colorectal (n=524), nasopharyngeal (n=143), gastric (n=102), biliary tree (n=81), nasopharyngeal (n=143) and ovarian (n=77) cancer. Single mutation corresponds to the presence of a pathogenic mutation in only one of these genes; co-mutation, to the presence of pathogenic mutations in ≥2 genes. We examined the status of single and co-mutations compared to disease stage and patient overall survival (OS) stratified by tumor type.

Results: Pathogenic mutations in any of the 4 genes were observed in 1337 (50% of all tumors) and co-mutation in 347 tumors (28% of tumors with mutations in these genes). Single mutations and co-mutations were observed in 481 (36.0%) and 322 (24.1%) tumors for TP53, respectively; in 350 (26.0%) and 198 (14.8%) for PIK3CA; in 80 (6%) and 198 (14.8%) for KRAS; and, in 51 (3.9%) and 120 (9.0%) for BRCA1. Co-mutations of BRCA1 and KRAS were more frequent than single mutations in the two genes across tumor types (p’s&lt;0.010). The same was observed for PIK3CA and TP53 except for breast cancer, where single mutations were more frequent than co-mutations (p’s&lt;0.001). Compared to stage I-III, stage IV tumors were more frequently mutated in TP53, KRAS and BRCA1 (p’s&lt;0.010) but were significantly less often mutated in PIK3CA (p&lt;0.001). Co-mutation rates for BRCA1, KRAS and TP53 did not differ between stage I-III and IV tumors but these were significantly different for PIK3CA (33.5% in I-III vs. 64.3% in IV; p&lt;0.001). Upon stratification by tumor type, in stage I-III disease, compared to tumors with co-mutations, single BRCA1, TP53 and KRAS mutations conferred similar OS, but single PIK3CA mutations conferred significantly lower risk for death (HR 0.52; 95%CI 0.35-0.77; p&lt;0.001). In stage IV disease, compared to no mutations, single KRAS or TP53 were associated with poor OS (p=0.017 and p=0.025, respectively) but this effect disappeared in patients with KRAS/TP53 co-mutated tumors.

Conclusions: Co-mutation patterns of known cancer drivers vary with respect to the affected gene, tumor type and disease stage. Known drivers have distinct prognostic impact when occurring singly or co-altered in the non-metastatic and metastatic setting, which may need to be considered in Precision Oncology trials.

Citation Format: Vassiliki Kotoula, Elena Fountzilas, Georgia-Angeliki Koliou, Kyriaki Papadopoulou, Eleni Giannoulatou, Ioannis Tikas, Flora Zagouri, Christos Christodoulou, Georgios Pentheroudakis, Angelos Koutras, Dimitrios Pectasides, George Fountzilas. Pathogenic drivers and their comutations in genes frequently altered in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 486.

Prognostic implications of mismatch repair deficiency in patients with nonmetastatic colorectal and endometrial cancer

Background

The clinical relevance of mismatch repair (MMR) status in patients with nonmetastatic cancer across tumour types remains unclear. Our goal was to investigate the prognostic role of MMR deficiency in patients with stage I-III colorectal and endometrial cancer.

Methods

Patients with nonmetastatic colorectal and endometrial cancer with tumour tissue available for analysis were identified through the Hellenic Cooperative Oncology Group (HeCOG)'s tumour repository. Patients had been referred to Departments of Medical Oncology affiliated with HeCOG. MMR protein expression was evaluated by immunohistochemistry. The primary outcome measure was overall survival (OS).

Results

From May 1990 to September 2012, 1158 patients with nonmetastatic colorectal (N = 991) and endometrial cancer (N = 167) were identified (median age: 64 years, men: 544). All patients with colorectal and 109 (65%) with endometrial cancer had received adjuvant treatment. MMR deficiency was observed in 114 (11.5%) of colorectal and 80 (47.9%) of endometrial tumours. More commonly deficient proteins were PMS2 (69 patients, 7%) and MLH1 (63 patients, 6.5%) in colorectal cancer and MSH2 (58 patients, 34.7%) in endometrial cancer. Colorectal MMR-deficient (dMMR) tumours were more likely to be right sided (65 % dMMR vs 27 % proficient MMR, pMMR; p < 0.001), high grade (31% vs 15%, χ², p < 0.001) and with a mucinous component (64% vs 42%, p < 0.001). Endometrial dMMR tumours were more often of endometrioid histology (51.4 % endometrioid vs 20 % serous/clear cell, p = 0.020). Compared with MMR proficiency, MMR deficiency was associated with improved OS in patients with endometrial cancer (HR = 0.38, 95% CI 0.20 to 0.76, p = 0.006), but not in patients with colorectal cancer (HR = 0.73, 95% CI 0.49 to 1.09, p = 0.130). After adjusting for age, stage and grade, MMR deficiency maintained its favourable prognostic significance in patients with endometrial cancer (HR = 0.42, 95% CI 0.20 to 0.88, p = 0.021).

Conclusions

DMMR was associated with improved outcomes in patients with nonmetastatic endometrial cancer, but not in patients with nonmetastatic colorectal cancer who received adjuvant chemotherapy.

Prognostic significance of tumor genotypes and CD8+ infiltrates in stage I-III colorectal cancer

Background

We explored the clinical significance of tumor genotypes and immunophenotypes in non-metastatic colorectal cancer (CRC).

Methods

In primary tumors (paraffin blocks) from 412 CRC patients treated with adjuvant chemotherapy, we examined pathogenic mutations (panel NGS; 347 informative); mismatch repair (MMR) immunophenotype (360 informative); and CD8+ lymphocyte density (high – low; 412 informative). The primary outcome measure was disease-free survival (DFS).

Results

We evaluated 1713 pathogenic mutations (median: 3 per tumor; range 0-49); 118/412 (28.6%) tumors exhibited high CD8+ density; and, 40/360 (11.1%) were MMR-deficient. Compared to MMR-proficient, MMR-deficient tumors exhibited higher CD8+ density (chi-square, p<0.001) and higher pathogenic mutation numbers (p=0.003). High CD8+ density was an independent favorable prognosticator (HR=0.49, 95%CI 0.29-0.84, Wald's p=0.010). Pathogenic BRCA1 and ARID1A mutations were inversely associated with each other (p<0.001), were not associated with MMR-deficiency or CD8+ density, but both independently predicted for unfavorable DFS (HR=1.98, 95%CI 1.12-3.48, p=0.018 and HR=1.99, 95%CI 1.11-3.54, p=0.020, respectively).

Conclusion

In non-metastatic CRC, high CD8+ lymphocyte density confers a favorable prognosis and may be developed as a single marker in routine diagnostics. The unfavorable prognostic effect of pathogenic BRCA1 and ARID1A mutations is a novel observation that, if further validated, may improve treatment selection.

Treating EGFR-Mutated Oncogene-Addicted Advanced Non-Small-Cell Lung Cancer in the Era of Economic Crisis in Greece: Challenges and Opportunities

PURPOSE

Because of the profound financial crisis that commenced in Greece in 2010, severe cuts in health care spending and other restriction measures led to significant delays in the reimbursement of novel antineoplastic agents. In 2011, the Hellenic Society of Medical Oncology initiated a program of early access to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors for the treatment of patients with advanced, EGFR-mutant non-small-cell lung cancer (NSCLC). We evaluated treatment patterns and clinical outcomes in patients with EGFR-mutant or wild-type disease treated at a large center in Greece throughout the period of financial crisis.

PATIENTS AND METHODS

From 2011 through 2015, 252 patients with newly diagnosed advanced NSCLC were treated at the Department of Medical Oncology of the Papageorgiou Hospital, a tertiary cancer center in northern Greece. We retrospectively reviewed patient medical records to obtain clinicopathologic characteristics, EGFR mutation status, and follow-up data. The primary end point was time to treatment failure.

RESULTS

Of the 198 evaluable patients, 25 (12%) had EGFR mutations. All patients with EGFR mutations except one received treatment with an EGFR tyrosine kinase inhibitor. Median times to treatment failure for patients with EGFR-mutant and wild-type disease were 15.8 and 7.1 months, respectively (hazard ratio, 0.58; 95% CI, 0.35 to 0.95; P = .031). There was no difference in overall survival between the two groups ( P = .293). No deviation from treatment guidelines or discontinuation of treatment regimens occurred because of logistic reasons or drug shortages.

CONCLUSION

Despite restrictions in the reimbursement policy and accompanying controls in the use of high-cost medicines, the national program enabled treatment of patients with EGFR-mutant NSCLC according to established guidelines. Therefore, the clinical outcomes of such patients treated in Greece during the economic crisis were in accordance with international standards.

A phase I clinical trial of hepatic arterial infusion of oxaliplatin and oral capecitabine, with or without intravenous bevacizumab, in patients with advanced cancer and predominant liver involvement

BACKGROUND

We investigated hepatic arterial infusion (HAI) oxaliplatin combined with capecitabine +/- bevacizumab in advanced cancer with predominant liver involvement.

METHODS

Patients received HAI oxaliplatin (140 mg/m²) and escalating doses of capecitabine (500, 750, and 1000 mg/m²), with (Group 1) or without (Group 2) bevacizumab (10 mg/kg IV). A 3 + 3 dose design was used, followed by an expansion phase.

RESULTS

From 9/2009 to 2/2014, 61 patients (34 men, 27 women) were enrolled (Group 1 = 44; Group 2 = 17). Patients were treated in Group 2 if they had contraindications to bevacizumab (n = 13) or if there was no opening in Group 1 (n = 4). The median age was 60 years (range, 20-88). The most common cancers were colorectal (22 patients), liver (12), pancreatic (7), breast (4), and biliary tract (4). The median number of prior therapies was 3 (range, 1-12); 32 (53%) patients had received oxaliplatin. The dose-limiting toxicity was Grade 3 diarrhea and occurred in 2 patients receiving 1000 mg/m² capecitabine. The maximum tolerated dose was HAI oxaliplatin 140 mg/m², capecitabine 750 mg/m², and bevacizumab 10 mg/kg. The most common toxicities were nausea/vomiting, anemia, thrombocytopenia, neutropenia, and hypomagnesemia. The rates of partial response and stable disease ≥ 4 months were 22% and 39% (Group 1) and 9% and 0% (Group 2). The respective median time to treatment failure and overall survival were 3 and 6.9 months (Group 1) and 1.5 and 5.9 months (Group 2).

CONCLUSION

HAI oxaliplatin combined with capecitabine +/- bevacizumab was well-tolerated and was associated with favorable outcomes in selected patients.

Overview of precision oncology trials: challenges and opportunities

INTRODUCTION

In recent years, the therapeutic management of selected patients with cancer has shifted toward the 'precision medicine' approach based on patient's mechanisms of tumorigenesis, and their baseline characteristics and comorbidities. Complete tumor and cell-free DNA profiling using next-generation sequencing, proteomic and RNA analysis, and immune mechanisms should to be taken into consideration and accurate bioinformatic analysis is essential to optimize patient's treatment. Areas covered: The challenges and opportunities of conducting clinical trials in precision oncology are summarized. Expert commentary: Precision medicine has significantly changed the diagnostic and therapeutic landscape of cancer. Successful implementation of precision medicine requires translational and bioinformatics infrastructure to support optimization of treatment selection. Targeted therapy, immunotherapy, T-cell therapy alone or in combination with cytotoxic or other effective therapeutic strategies and innovative clinical trials with adaptive design should be offered to all patients. Data sharing and 'N-of-1' models hold the promise to optimize the treatment of individual patients and expedite drug approval for rare alterations and tumor types. Artificial intelligence will facilitate accurate utilization of sequencing data to perform algorithm analysis. Collaboration of healthcare providers with pharmaceutical and biotechnical companies, scientific organizations, and governmental regulatory agencies have a crucial role in curing cancer.

Abstract 1359: Somatic involution of pathogenic BRCA1 germline mutations

There is currently a wealth of data on the tumor genomic contexture from BRCA1/2 carriers, particularly breast and ovarian carcinomas. By contrast, little attention has as yet been paid to the genomic status of cancer-related normal tissues from these individuals. Here, we investigated the status of pathogenic BRCA1 germline mutations (GM) in breast (B) and gynecologic (GYN) tissues.

Methods: We examined 121 DNA samples (48 B; 36 GYN; 37 tumors) from an equal number of paraffin blocks obtained upon prophylactic or debulking surgery from 44 BRCA1/2 carriers (mean age 38 yrs, range 24-62; 43 BRCA1 carriers). Six women had never had cancer manifestation (CM). At the time of surgery, 32 were cancer-free but had received neo- or adjuvant chemotherapy, and 6 had concurrent cancer without prior treatment. Following multimethod DNA quality control, mutation validation and sample identity match to exclude false negatives, we interrogated GM presence in tissues in comparison to clinicopathologic data and tumor genotypes (60-gene panel; mean read depth over 800).

Results: In 19 samples from 13 BRCA1 carriers, including 13 normal B/GYN and 6 tumors, the germline mutation was present at frequencies lower than 5% (observed with the integrated genome viewer) up to 12%, or it was undetectable with Sanger sequencing and multiplex PCR. This condition, termed GM-loss, was present in 13 GYN, 12 of which in the histologically normal tube, and in only 3 B with fibrocystic disease (p=0.0210). It was also present in one ovarian thecoma but it was absent in usual or atypical hyperplasia in B. GM-loss was observed in 9/55 normal tissues from breast cancer and in 4/6 normal tissues from ovarian cancer patients, while it was absent in the normal tissues from women without CM (p=0.0002). GM-loss mostly affected the BRCA1 BRCT functional domain (p&lt;0.0001) and concerned large deletions (10/17 samples), small indels (5/32; 15.6%) and less so single-nucleotide substitutions (4/66; 6.0%; p&lt;0.0001). Normal tissue GM-loss was rather localized, e.g., in 10 patients with multiple samples it was present in only one B or fallopian tube. It was, however, related to the status of concurrent ovarian tumors in 3/6 cases. In the normal tube of these patients, next to the low-frequency GM a somatic pathogenic BRCA1 mutation was present at 25-41% allelic frequency; the same was observed in one breast tumor after neoadjuvant chemotherapy. Three of the replaced GMs were indels, two corresponded to the well-known BRCA1 p.Q1777fs, and all novel mutations were missense.

Conclusions: We observed BRCA1 GM-loss in normal tissues, breast and mostly fallopian tube, in about 30% of the carriers in the present cohort, all with previous or concurrent cancer. The phenomenon seems analogous to the GM reversion described in tumors but, as shown, it may also occur in the absence of prior treatment. Its origin and impact on cancer dynamics and therapeutic approaches seem worth further pursuing with functional studies.

Citation Format: Vassiliki Kotoula, Efterpi Demiri, Florentia Fostira, Eleni Vrettou, Kyriaki Papadopoulou, Ioannis Tikas, Konstantinos Papazisis, Thomas Zaramboukas, Asimina Asimaki-Vlachopoulou, Spyridon Miliaras, Elena Fountzilas, Ananias Ananiadis, Sofia Chrisafi, Christos Poulios, Ioannis Natsiopoulos, Aris Tsiftsoglou, George Fountzilas. Somatic involution of pathogenic BRCA1 germline mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1359.

Abstract P3-04-04: Germline and somatic mutation status in tissues from BRCA1/2 carriers

Background – aim: In carriers of BRCA1/2 pathogenic mutations (mut), it is expected that the germline mut is present in all tissues, particularly in normal; the somatic mut status in normal tissues from these patients is usually not addressed. We investigated the mut status in normal and tumor tissues in a real-life cohort of BRCA1/2 carriers who underwent prophylactic surgery.

Methods: All 53 women had known BRCA1/2 germline mut that had been assessed independently; 42 had previous cancer manifestation (PCM); all had prophylactic mastectomy; 22 had prophylactic hystero-salpingo-oophorectomy. By using a 60-gene NGS panel, we examined the mut status of 231 samples, 39 peripheral blood and 192 paraffin tissues (FFPE: 46 tumors, out of which 43 breast; 97 normal breast [NB]; 49 normal ovary and salpinx [NGYN]). Germline mut status was interrogated in tissues with the above panel, Sanger sequencing and a multiplex PCR protocol for large exonic deletions, along with extensive FFPE DNA quality control (QC) to exclude false negatives.

Results: Eight patients carried germline BRCA2 and 45 BRCA1 mut (29 in the BRCT-domain; 31 substitutions/indels). We identified somatic mut in 85% of the tumors and in 64% of the normal samples; mut were found significantly more often (p=0.003) and in higher numbers (p&lt;0.001) in NGYN than in NB. In NB and NGYN, top 3 genes with somatic mut were BRCA2 (28%), BRCA1 (17%), TP53 (7%). In tumors, somatic mut were most frequent in TP53 (49%; p&lt;0.001) and BRCA1 (38%; p=0.039). Among all tissue types, the 5 tumors post-neoadjuvant treatment had the highest and NB the lowest mut load (p=0.001). In NB and NGYN, mut load was not affected by PCM or BRCA1 mut domain but it was higher in BRCA1 vs. BRCA2 carriers (p=0.027) and in those with BRCA1 substitutions/indels vs. exon deleting and skipping mut (p&lt;0.001). In tumors, germline BRCA1 substitutions/indels were associated with higher mut load (p=0.014). We validated germline mut status in all blood samples and in 111 tissue samples that passed FFPE DNA QC from 40 patients. The germline mut was not found in 14 samples (4 breast tumors; 3 NB; 7 NGYN) from 10 (25%) patients, all BRCA1 carriers, 9 with germline mut in the BRCT-domain. The only non-BRCT domain germline mut that was lost in one breast tumor, p.V1234fs, was replaced by the R1751* (validated), again in the BRCT domain. In normal tissues, those with lost germline mut had significantly less somatic mut compared to those with preserved germline mut (p&lt;0.001).

Conclusions: In BRCA1/2 carriers, somatic mut in BRCA genes and TP53 are present in normal breast and GYN tissues, more frequently in the latter, and seem associated with the mutated gene and with the type of mut in the germline. The mut status of normal breast tissue does not seem to be affected by neoadjuvant chemotherapy for breast cancer. The observed BRCA1 germline mut loss, particularly in normal tissues, may be approached as a negative selection for the inherited mut; similarly to the described germline mut reversion after chemotherapy, tissues may react to deleterious effects of haploinsufficiency, which needs functional validation.

Citation Format: Kotoula V, Demiri E, Fostira F, Vrettou E, Papadopoulou K, Tikas I, Papazisis K, Zaramboukas T, Asimaki-Vlachopoulou A, Miliaras S, Fountzilas E, Ananiadis A, Chrisafi S, Poulios C, Natsiopoulos I, Tsiftsoglou A, Fountzilas G. Germline and somatic mutation status in tissues from BRCA1/2 carriers [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 P3-04-04.