Germline cancer susceptibility mutations in older women with breast cancer (BC).

Abstract

e13030 Background: Older women with BC are less likely to undergo genetic cancer risk assessment since a hallmark of hereditary BC is younger age at onset. Hence there are limited data regarding genetic risk assessment findings in older women with BC. We analyzed the clinical characteristics and germline variant profiles of women with history of BC referred for genetic counseling at age ≥ 65 years, enrolled in the Clinical Cancer Genomics Community Research Network registry. Methods: Women age ≥ 65 with a history of BC (invasive or ductal carcinoma in situ) who underwent genetic testing from 1997 to 2016 were included. The profile of those found to have BC-related pathogenic variants was analyzed. Demographic and clinical characteristics for those with and without germline variants were compared using Fisher’s test and x2statistics. Results: 1372 women age ≥ 65 with BC were identified. Genetic testing was performed in 75% (n = 1035), among whom 10.4% (n = 108) had a germline variant in a BC-associated gene. High risk gene variants accounted for 85.1% (n = 92): BRCA2 (41.6%, n = 45), BRCA1 (37%, n = 40), PALB2 (5.5%, n = 6) and TP53 ( < 1%, n = 1). Moderate risk gene variants were identified in 16.6% (n = 18): CHEK2 (13.8%, n = 15), ATM (1.8%, n = 2) and NF1 ( < 1%, n = 1). Mean age at BC diagnosis was 56.4 (range 29 - 84) for women with variants and 60.9 (range 20 - 90) for those without (p < .001). 25.9% of women with variants (n = 28) had their first BC diagnosed ≥ age 65, of which 60.7% (n = 17) were BRCA2 and 21.4% (n = 6) were BRCA1 mutations ( BRCA2 was significantly higher in women diagnosed with BC age ≥ 65 [p < .001]). There was no difference in the mean number of 1st, 2nd and 3rd degree relatives with BC (2.4 [range 0-10] vs 2.2 [range 0-15]) for women with and without variants, respectively, and no difference in stage at diagnosis (Stage I-II in 95% vs 89.5%, p = .4). Women with variants were less likely to have ER/PR positive tumors than those without (66% vs 81.6%, p = .01). Conclusions: BC related susceptibility variants, particularly in BRCA2, are found in a significant number of older women undergoing genetic testing for a first diagnosis of BC ≥ 65. Older women with a clinical suspicion of hereditary BC should not be excluded from genetic testing and counseling based on chronological age alone.