Analysis of clinical characteristics in breast cancer patients with the Japanese founder mutation of BRCA1 L63X.

Abstract

22 Background: Hereditary breast and ovarian cancer (HBOC) is a high-penetrance inherited disease, and founder mutation has been reported in the West. However, there are yet no reports of founder mutation of HBOC on breast cancer in the Japanese population. In this study, we report the breast cancer clinical characteristics of L63X, which is one of the founder mutations in BRCA1 in the Japanese population. Methods: Data on 223 affected breast cancer patients (28 BRCA1 carriers, 19 BRCA2 carriers, and 176 non-carriers) were collected at Showa University in Tokyo from September 2010 to June 2015. In 22 independent mutations of BRCA1, the L63X mutation was detected in 9 patients. Data regarding the age of breast cancer onset, pathological features, clinical features, and family history were collected. Results: The age of onset was no significant differences between the L63X mutation and other BRCA1 mutations (39.7 vs. 38.5years). The proportion of triple negative breast cancer patients was 87.5% in the L63X mutation carriers and 89.5% in other BRCA1 mutation carriers. No patients of the L63X affected bilateral breast cancers. On the other hand, 36.7% of other BRCA1mutations affected bilateral breast cancers. There was no significant difference in pathological features (intrinsic subtype, nuclear grade and ki-67 index). The L63X carriers tended to have a family history of breast cancers. All L63X mutations were detected in the Eastern part of Japan. Conclusions: The breast cancer clinical characteristics of L63X might be considered no different from other types of BRCA1 mutations. Recently, it has been reported that breast and ovarian cancer risks varied according to the type and location of BRCA1/2 mutations. L63X mutation is located in the breast cancer cluster region in BRCA1. Further investigation is necessary for appropriate validation and accumulation of data.