CJH Kramer

Causality and functional relevance of BRCA1 and BRCA2 pathogenic variants in non‐high‐grade serous ovarian carcinomas

Abstract The identification of causal BRCA1/2 pathogenic variants (PVs) in epithelial ovarian carcinoma (EOC) aids the selection of patients for genetic counselling and treatment decision‐making. Current recommendations therefore stress sequencing of all EOCs, regardless of histotype. Although it is recognised that BRCA1/2 PVs cluster in high‐grade serous ovarian carcinomas (HGSOC), this view is largely unsubstantiated by detailed analysis. Here, we aimed to analyse the results of BRCA1/2 tumour sequencing in a centrally revised, consecutive, prospective series including all EOC histotypes. Sequencing of n  = 946 EOCs revealed BRCA1/2 PVs in 125 samples (13%), only eight of which were found in non‐HGSOC histotypes. Specifically, BRCA1/2 PVs were identified in high‐grade endometrioid (3/20; 15%), low‐grade endometrioid (1/40; 2.5%), low‐grade serous (3/67; 4.5%), and clear cell (1/64; 1.6%) EOCs. No PVs were identified in any mucinous ovarian carcinomas tested. By re‐evaluation and using loss of heterozygosity and homologous recombination deficiency analyses, we then assessed: (1) whether the eight ‘anomalous’ cases were potentially histologically misclassified and (2) whether the identified variants were likely causal in carcinogenesis. The first ‘anomalous’ non‐HGSOC with a BRCA1/2 PV proved to be a misdiagnosed HGSOC. Next, germline BRCA2 variants, found in two p53‐abnormal high‐grade endometrioid tumours, showed substantial evidence supporting causality. One additional, likely causal variant, found in a p53‐wildtype low‐grade serous ovarian carcinoma, was of somatic origin. The remaining cases showed retention of the BRCA1/2 wildtype allele, suggestive of non‐causal secondary passenger variants. We conclude that likely causal BRCA1/2 variants are present in high‐grade endometrioid tumours but are absent from the other EOC histotypes tested. Although the findings require validation, these results seem to justify a transition from universal to histotype‐directed sequencing. Furthermore, in‐depth functional analysis of tumours harbouring BRCA1/2 variants combined with detailed revision of cancer histotypes can serve as a model in other BRCA1/2 ‐related cancers. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Prognostic Relevance of Molecular Classification in Endometrial Cancer: Insights From a South African Cohort

PURPOSE Geographical and racial diversity may influence endometrial cancer (EC) prognosis, yet its impact remains underexplored. In South Africa (SA), the rising incidence of EC underscores the need to investigate potential biologic differences. Molecular classification of EC offers valuable prognostic insights that could help address disparities and improve care. This study evaluated the prevalence and prognostic significance of molecular subtypes in a South African high-intermediate and high-risk EC cohort. MATERIALS AND METHODS We included 133 patients with high-intermediate and high-risk EC diagnosed in SA between January 2017 and December 2021. Clinical, demographic (including self-identified race), and follow-up data were collected. Central pathology review assessed histotype, grade, lymphovascular space invasion, and International Federation of Gynecology and Obstetrics 2009 stage. Molecular subtyping followed the WHO 2020 algorithm using targeted next-generation sequencing and immunohistochemistry for p53, mismatch repair (MMR) proteins, and ER. Shallow whole-genome sequencing (sWGS) assessed genome-wide copy number alterations. RESULTS Among 131 patients with complete molecular classification, the most common subtype was p53-abnormal (p53abn, n = 71; 54.2%), followed by MMR-deficient (MMRd, n = 30; 22.9%), no specific molecular profile (NSMP, n = 21; 16.0%), and POLE -ultramutated ( POLE mut, n = 9; 6.9%). Nonendometrioid EC (NEEC) predominated (n = 82; 61.7%). High-grade endometrioid EC and NEEC were more frequent in non-White patients ( P = .030). Molecular subtypes were significantly associated with overall recurrence ( P = .029), with no recurrences in POLE mut ECs and the worst outcomes in p53abn ECs. sWGS revealed higher CN burdens in p53abn ECs, with recurrent focal alterations involving CCNE1 amplification and RB1 loss. CONCLUSION To our knowledge, this study is the first to demonstrate the prognostic value of EC molecular classification in a South African cohort. These findings support the global relevance of molecular EC subtyping. The urgent need for access to molecular diagnostics or cost-effective alternatives in resource-limited settings is highlighted.

Clinical Behavior and Molecular Landscape of Stage I p53-Abnormal Low-Grade Endometrioid Endometrial Carcinomas

Abstract Purpose: The clinical significance of the p53-abnormal (p53abn) molecular subtype in stage I low-grade endometrioid endometrial carcinoma (EEC) is debated. We aimed to review pathologic and molecular characteristics, and outcomes of stage I low-grade p53abn EEC in a large international cohort. Experimental Design: Previously diagnosed stage I p53abn EC (POLE–wild-type, mismatch repair–proficient) low-grade EEC from Canadian retrospective cohorts and PORTEC-1&2 trials were included. Pathology review was performed by six expert gynecologic pathologists blinded to p53 status. IHC profiling, next-generation sequencing, and shallow whole-genome sequencing was performed. Kaplan–Meier method was used for survival analysis. Results: We identified 55 stage I p53abn low-grade EEC among 3,387 cases (2.5%). On pathology review, 17 cases (31%) were not diagnosed as low-grade EEC by any pathologists, whereas 26 cases (47%) were diagnosed as low-grade EEC by at least three pathologists. The IHC and molecular profile of the latter cases were consistent with low-grade EEC morphology (ER/PR positivity, patchy p16 expression, PIK3CA and PTEN mutations) but they also showed features of p53abn EC (TP53 mutations, many copy-number alterations). These cases had a clinically relevant risk of disease recurrence (5-year recurrence-free survival 77%), with pelvic and/or distant recurrences observed in 12% of the patients. Conclusions: A subset of p53abn EC is morphologically low-grade EEC and exhibit genomic instability. Even for stage I disease, p53abn low-grade EEC are at substantial risk of disease recurrence. These findings highlight the clinical relevance of universal p53-testing, even in low-grade EEC, to identify women at increased risk of recurrence.

Evaluation of BRCA1/2 testing rates in epithelial ovarian cancer patients: lessons learned from real-world clinical data

Abstract Identification of somatic and germline BRCA1/2 pathogenic variants in epithelial ovarian cancer (EOC) patients is essential for determining poly-(ADP-ribose)-polymerase (PARP) inhibitor sensitivity and genetic predisposition. In the Netherlands, BRCA1/2 testing changed to a tumor-first approach to efficiently identify both somatic and germline pathogenic variants in all patients. Here, we performed an in-depth evaluation of the first four years of the tumor-first test-pathway. Data of consecutive series of patients diagnosed with EOC in two regions were obtained from the Netherlands Cancer Registry. Tumor and/or germline test data were retrieved from hospital databases. The primary outcome was the percentage of patients completing the BRCA1/2 test-pathway, defined as having a negative tumor test or a referral for a germline test in case of a positive tumor test or no tumor test. Factors associated with test-pathway completion were identified through multivariable logistic regression analysis. In total, 69.8% (757/1085) completed the test-pathway. This was 74.4% in the most recent year. Younger patients, patients diagnosed in year three or four, patients with high-grade serous/high-grade endometrioid carcinoma, advanced stage disease, middle or high socioeconomic status, and patients who underwent surgery or chemotherapy, were more likely to complete the test-pathway. We report inequalities in genetic testing access in EOC patients, which highlight the need for better guideline adherence, particularly in older patients, those with low socioeconomic status, low-grade histotypes, early-stage disease and those without surgery or chemotherapy. Additionally, timely testing of patients, and testing relatives if patients cannot be tested, are crucial to increase test uptake.

Performance of a RAD51-based functional HRD test on paraffin-embedded breast cancer tissue

Abstract Purpose BRCA-deficient breast cancers (BC) are highly sensitive to platinum-based chemotherapy and PARP inhibitors due to their deficiency in the homologous recombination (HR) pathway. However, HR deficiency (HRD) extends beyond BRCA-associated BC, highlighting the need for a sensitive method to enrich for HRD tumors in an alternative way. A promising approach is the use of functional HRD tests which evaluate the HR capability of tumor cells by measuring RAD51 protein accumulation at DNA damage sites. This study aims to evaluate the performance of a functional RAD51-based HRD test for the identification of HRD BC. Methods The functional HR status of 63 diagnostic formalin-fixed paraffin-embedded (FFPE) BC samples was determined by applying the RAD51-FFPE test. Samples were screened for the presence of (epi)genetic defects in HR and matching tumor samples were analyzed with the RECAP test, which requires ex vivo irradiated fresh tumor tissue on the premise that the HRD status as determined by the RECAP test faithfully represented the functional HR status. Results The RAD51-FFPE test identified 23 (37%) of the tumors as HRD, including three tumors with pathogenic variants in BRCA1/2. The RAD51-FFPE test showed a sensitivity of 88% and a specificity of 76% in determining the HR-class as defined by the RECAP test. Conclusion Given its high sensitivity and compatibility with FFPE samples, the RAD51-FFPE test holds great potential to enrich for HRD tumors, including those associated with BRCA-deficiency. This potential extends to situations where DNA-based testing may be challenging or not easily accessible in routine clinical practice. This is particularly important considering the potential implications for treatment decisions and patient stratification.