Pritchard, Colin C.

Importance Half of all carriers of inherited cancer-predisposing variants in BRCA1 and BRCA2 are male, but the implications for their health are underrecognized compared to female individuals. Germline variants in BRCA1 and BRCA2 (also known as pathogenic or likely pathogenic variants, referred to here as BRCA1/2 PVs) are well known to significantly increase the risk of breast and ovarian cancers in female carriers, and knowledge of BRCA1/2 PVs informs established cancer screening and options for risk reduction. While risks to male carriers of BRCA1/2 PVs are less characterized, there is convincing evidence of increased risk for prostate cancer, pancreatic cancer, and breast cancer in males. There has also been a rapid expansion of US Food and Drug Administration–approved targeted cancer therapies, including poly ADP ribose polymerase (PARP) inhibitors, for breast, pancreatic, and prostate cancers associated with BRCA1/2 PVs. Observations This narrative review summarized the data that inform cancer risks, targeted cancer therapy options, and guidelines for early cancer detection. It also highlighted areas of emerging research and clinical trial opportunities for male BRCA1/2 PV carriers. These developments, along with the continued relevance to family cancer risk and reproductive options, have informed changes to guideline recommendations for genetic testing and strengthened the case for increased genetic testing for males. Conclusions and Relevance Despite increasing clinical actionability for male carriers of BRCA1/2 PVs, far fewer males than female individuals undergo cancer genetic testing. Oncologists, internists, and primary care clinicians should be vigilant about offering appropriate genetic testing to males. Identifying more male carriers of BRCA1/2 PVs will maximize opportunities for cancer early detection, targeted risk management, and cancer treatment for males, along with facilitating opportunities for risk reduction and prevention in their family members, thereby decreasing the burden of hereditary cancer.

Abstract Background Genomic biomarkers that predict response to anti-PD1 therapy in prostate cancer are needed. Frameshift mutations are predicted to generate more neoantigens than missense mutations; therefore, we hypothesized that the number or proportion of tumor frameshift mutations would correlate with response to anti-PD1 therapy in prostate cancer. Methods To enrich for response to anti-PD1 therapy, we assembled a multicenter cohort of 65 men with mismatch repair-deficient (dMMR) prostate cancer. Patient characteristics and outcomes were determined by retrospective chart review. Clinical somatic DNA sequencing was used to determine tumor mutational burden (TMB), frameshift mutation burden, and frameshift mutation proportion (FSP), which were correlated to outcomes on anti-PD1 treatment. We subsequently used data from a clinical trial of pembrolizumab in patients with nonprostatic dMMR cancers of various histologies as a biomarker validation cohort. Results Nineteen of 65 patients with dMMR metastatic castration-resistant prostate cancer were treated with anti-PD1 therapy. The PSA50 response rate was 65%, and the median progression-free survival (PFS) was 24 (95% confidence interval 16–54) weeks. Tumor FSP, more than overall TMB, correlated most strongly with prolonged PFS and overall survival (OS) on anti-PD1 treatment and with density of CD8+ tumor-infiltrating lymphocytes. High FSP similarly identified patients with longer PFS as well as OS on anti-PD1 therapy in a validation cohort. Conclusion Tumor FSP correlated with prolonged efficacy of anti-PD1 treatment among patients with dMMR cancers and may represent a new biomarker of immune checkpoint inhibitor sensitivity. Implications for Practice Given the modest efficacy of immune checkpoint inhibition (ICI) in unselected patients with advanced prostate cancer, biomarkers of ICI sensitivity are needed. To facilitate biomarker discovery, a cohort of patients with DNA mismatch repair-deficient (dMMR) prostate cancer was assembled, as these patients are enriched for responses to ICI. A high response rate to anti-PD1 therapy in these patients was observed; however, these responses were not durable in most patients. Notably, tumor frameshift mutation proportion (FSP) was identified as a novel biomarker that was associated with prolonged response to anti-PD1 therapy in this cohort. This finding was validated in a separate cohort of patients with nonprostatic dMMR cancers of various primary histologies. This works suggests that FSP predicts response to anti-PD1 therapy in dMMR cancers, which should be validated prospectively in larger independent cohorts.

PURPOSE Germline testing (GT) is a central feature of prostate cancer (PCA) treatment, management, and hereditary cancer assessment. Critical needs include optimized multigene testing strategies that incorporate evolving genetic data, consistency in GT indications and management, and alternate genetic evaluation models that address the rising demand for genetic services. METHODS A multidisciplinary consensus conference that included experts, stakeholders, and national organization leaders was convened in response to current practice challenges and to develop a genetic implementation framework. Evidence review informed questions using the modified Delphi model. The final framework included criteria with strong (> 75%) agreement (Recommend) or moderate (50% to 74%) agreement (Consider). RESULTS Large germline panels and somatic testing were recommended for metastatic PCA. Reflex testing—initial testing of priority genes followed by expanded testing—was suggested for multiple scenarios. Metastatic disease or family history suggestive of hereditary PCA was recommended for GT. Additional family history and pathologic criteria garnered moderate consensus. Priority genes to test for metastatic disease treatment included BRCA2, BRCA1, and mismatch repair genes, with broader testing, such as ATM, for clinical trial eligibility. BRCA2 was recommended for active surveillance discussions. Screening starting at age 40 years or 10 years before the youngest PCA diagnosis in a family was recommended for BRCA2 carriers, with consideration in HOXB13, BRCA1, ATM, and mismatch repair carriers. Collaborative (point-of-care) evaluation models between health care and genetic providers was endorsed to address the genetic counseling shortage. The genetic evaluation framework included optimal pretest informed consent, post-test discussion, cascade testing, and technology-based approaches. CONCLUSION This multidisciplinary, consensus-driven PCA genetic implementation framework provides novel guidance to clinicians and patients tailored to the precision era. Multiple research, education, and policy needs remain of importance.