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Prevalence and differentiation of hereditary breast and ovarian cancer in Japan.
J Clin Oncol 31, 2013 (suppl; abstr 1534)
Abstracts that were granted an exception in accordance with ASCO's Conflict of Interest Policy are designated with a caret symbol (^).
Background: Breast cancer is the most common female cancer, according to the Center for Cancer Control and Information Service in Japan. However, the lifetime breast cancer risk in Japan is markedly lower (one in 16) than in the U.S. or Europe. We assembled needed data on the prevalence and characteristics of BRCA1/2 in Japan. Methods: Our study of BRCA 1 and 2 (BRCA1/2) collected data at 8 institutions in Japan on 320 individuals with a strong family history of breast cancer, according to the NCCN guidelines, by the end of March, 2012. Results: Among 260 proband cases, 46 (17.7%) were positive for BRCA1 and 35 (13.5%) were BRCA2 positive. Therefore, the total pathological mutation rate was 30.7%. Pathology data after breast surgery were obtained from 35 cases of BRCA1 mutation, 22 (62.9%) of which were triple negative and 10 (29.4%) were Luminal type. On the other hand, 24 cases (85.7%) of BRCA2 mutations were Luminal type. The most prevalent BRCA1 mutation site was L63X, found in 10 families. L63X was reported previously by studies in Japan, and it may be a founder mutation. We found 2 cases of large deletion detected by MLPA, comprising the first two reported cases in Japan. One was an entire deletion of exon 20 and the lacked exons 1-9. Eight cases of BRCA1 (3.1%) and 12 (4.6%) BRCA2 were uncertain variants. TN with a family history ovarian cancer were 14/20 (70%), TN under 40 y/o 17/23 (73.9%) and TN with one or more breast cancers in family history 19/32 (59.4%) showed higher incidences of BRCA1/2, especially BRCA1. Conclusions: HBOC may have nearly the same prevalence in Japan as in the U.S. or Europe. If TN cases are taken into account, the ratio of BRCA1 is higher. L63X may be one of the founder mutations in Japan. A nationwide database of HBOC is important to address these challenges: (1) To develop risk models for BRCA1/2 carriers in Japan (2) To identify the proper methods to detect cancer occurrence among Japanese BRCA1/2 carrier early (3) To differentiate whether uncertain mutation variants found in Japan are deleterious.