Abstract 2548: Cancer in first-degree relatives of women with early-onset breast cancer: a comparison of self-reported and cancer registry data

Abstract

Abstract Background Breast cancer (BC) is the most common cancer in women, both world-wide and in Sweden. However, only about 2% occur in women ≤35 years of age. The aim of this study was to compare self-reported and registry data of family history of cancer, tumor characteristics and BRCA germline mutation status in women with early-onset BC. Materials and methods Between January 1st 1990 and December 31st 2013, a total of 779 women aged ≤35 years were diagnosed with BC in the South Swedish Health Care Region. Of these women, 231 women sought, or were referred for, genetic counseling at the Oncogenetic Clinic, Lund, Sweden, and were included in the study. Subsequently, 224 women were screened for germline mutations. Self-reported information about family history of cancer in first-degree relatives (parents, siblings and children) was obtained from the participants and was compared with data from the Swedish Cancer Registry. When available, hormone receptor (ER and PR) and HER2 status of the tumors was collected from pathology reports. Fisher's Exact Test was performed to estimate odds ratios (ORs) with 95% confidence intervals (CIs). Results Mutation analyses revealed 143 (63.8%) cases without mutations (BRCAX), 46 (20.5%) with BRCA1, 19 (8.5%) with BRCA2 and 16 (7.1%) with other mutations (TP53, CHEK2, PTEN, PALB2, CDH1 and MSH2/MSH6). Family history of BC and ovarian cancer (OvC) in first-degree relatives was self-reported in equal numbers as registry data. Family history of BC was found in ∼30% of the cases, and of OvC in ∼3%. However, family history of other types of cancer was self-reported in 13 (5.6%) and registry-reported in 58 (25.1%) cases (OR, 18.8; 95% CI, 3.91-180; p<0.001). Of the registry-reported cancers, cervical and skin cancers were the most common when diagnosed before the genetic counseling sessions, and when diagnosed after, prostate and skin cancers were the most common. When comparing tumor characteristics of BRCA1 with BRCAX cases, mutation carriers more often showed receptor negative tumors: ER- (OR, 13.4; 95% CI, 3.77-73.5; p<0.001), PR- (OR, 47.9; 95% CI, 7.34-2011; p<0.001) and HER2- (OR, 17.1; 95% CI, 1.81-inf; p<0.004). Conclusion The main findings in this study of early-onset BC were that cases with germline mutations in the BRCA1 and BRCA2 genes were exceptional high, that cervical cancer was the most common not self-reported cancer in first-degree relatives diagnosed before the genetic counseling, and that BRCA1 carriers had a higher rate of ER, PR and HER2 negative tumors, which tends to indicate a less favorable prognosis. When assessing the need for mutation screening, as shown previously by others, oncologists and genetic counselors need to consider both early-onset BCs and receptor negative tumors as predictors for BRCA1 mutations, and when obtaining information about family history of cancers, patients might lack information about cervical cancers in relatives. Citation Format: Annelie Augustinsson, Ulf Kristoffersson, Håkan Olsson. Cancer in first-degree relatives of women with early-onset breast cancer: a comparison of self-reported and cancer registry data. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2548.