Mutation Rates in Cancer Susceptibility Genes in Patients With Breast Cancer With Multiple Primary Cancers.

PURPOSE: Women with breast cancer have a 4%-16% lifetime risk of a second primary cancer. Whether mutations in genes other than BRCA1/2 are enriched in patients with breast and another primary cancer over those with a single breast cancer (S-BC) is unknown. PATIENTS AND METHODS: We identified pathogenic germline mutations in 17 cancer susceptibility genes in patients with BRCA1/2-negative breast cancer in 2 different cohorts: cohort 1, high-risk breast cancer program (multiple primary breast cancer [MP-BC], n = 551; S-BC, n = 449) and cohort 2, familial breast cancer research study (MP-BC, n = 340; S-BC, n = 1,464). Mutation rates in these 2 cohorts were compared with a control data set (Exome Aggregation Consortium [ExAC]). RESULTS: Overall, pathogenic mutation rates for autosomal, dominantly inherited genes were higher in patients with MP-BC versus S-BC in both cohorts (8.5% v 4.9% [P = .02] and 7.1% v 4.2% [P = .03]). There were differences in individual gene mutation rates between cohorts. In both cohorts, younger age at first breast cancer was associated with higher mutation rates; the age of non-breast cancers was unrelated to mutation rate. TP53 and MSH6 mutations were significantly enriched in patients with MP-BC but not S-BC, whereas ATM and PALB2 mutations were significantly enriched in both groups compared with ExAC. CONCLUSION: Mutation rates are at least 7% in all patients with BRCA1/2 mutation-negative MP-BC, regardless of age at diagnosis of breast cancer, with mutation rates up to 25% in patients with a first breast cancer diagnosed at age < 30 years. Our results suggest that all patients with breast cancer with a second primary cancer, regardless of age of onset, should undergo multigene panel testing.

Genetic cancer predisposition syndromes among older adults.

Earlier age at onset is one characteristic of hereditary cancer syndromes, so most studies of genetic testing have focused on young patients with cancer. However, recent studies of multigene panel tests in unselected cancer populations have detected a considerable proportion of older patients with germline pathogenic variants (PVs) in cancer susceptibility genes. As the number of older patients with cancer continues to rise, clinicians should be aware of genetic/genomic cancer risk assessment (GCRA) criteria in both young and older adults. Identifying individuals with a germline PV in a cancer susceptibility gene may be important for precision therapy of current cancers and screening and prevention of new primary cancers, as well as cascade testing to identify high cancer risks for family members. Typically, hereditary predisposition germline genetic testing has been recommended for patients with early onset cancers and/or a family history of cancer. However, more recently international guidelines recommend testing for potential therapeutic intervention regardless of age for some tumors frequently seen in older patients, such as epithelial ovarian, pancreatic, and metastatic prostate and breast cancers. GCRA in older patients may present challenges including: clonal hematopoiesis (CH) confounding test interpretation, ethical aspects (autonomy, nonmaleficence, beneficence), patient health status, comorbidities, as well as lack of insurance coverage. These factors should be considered during genetic counseling and when considering cancer screening and risk reduction procedures. This manuscript reviews available data on common hereditary cancer syndromes in older patients and provides tools to help providers perform GCRA in this population.

The Burden of Breast Cancer Predisposition Variants Across The Age Spectrum Among 10 000 Patients.

BACKGROUND/OBJECTIVES: Women diagnosed with breast cancer (BC) at an older age are less likely to undergo genetic cancer risk assessment and genetic testing since the guidelines and referrals are biased toward earlier age at diagnosis. Thus, we determined the prevalence and type of pathogenic cancer predisposition variants among women with a history of BC diagnosed at the age of 65 years or older vs younger than 65 years. DESIGN: Prospective registration cohort. SETTING: The Clinical Cancer Genomics Community Research Network, including 40 community-based clinics in the United States and 5 in Latin America. PARTICIPANTS: Women with BC and genetic testing results. MEASUREMENTS: Sociodemographic characteristics, clinical variables, and genetic profiles were compared between women aged 65 years and older and those younger than 65 years at BC diagnosis. RESULTS: Among 588 women diagnosed with BC and aged 65 years and older and 9412 diagnosed at younger than 65 years, BC-associated pathogenic variants (PVs) were detected in 5.6% of those aged 65 years and older (n = 33) and 14.2% of those younger than 65 years (n = 1340) (P < .01). PVs in high-risk genes (eg, BRCA1 and BRCA2) represented 81.1% of carriers among women aged 65 years and older (n = 27) and 93.1% of those younger than 65 years (n = 1248) (P = .01). BRCA2 PVs represented 42.4% of high-risk gene findings for those aged 65 years and older, whereas BRCA1 PVs were most common among carriers younger than 65 years (49.7%). PVs (n = 7) in moderate-risk genes represented 21.2% for carriers aged 65 years and older and 7.3% of those younger than 65 years (n = 98; P < .01). CHEK2 PVs were the most common moderate-risk gene finding in both groups. CONCLUSION: Clinically actionable BC susceptibility PVs, particularly in BRCA2 and CHEK2, were relatively prevalent among older women undergoing genetic testing. The significant burden of PVs for older women with BC provides a critical reminder to recognize the full spectrum of eligibility and provide genetic testing for older women, rather than exclusion based on chronological age alone. J Am Geriatr Soc 67:884-888, 2019.