Abstract
Age‐adjusted incidence rates of breast cancer vary more than 10‐fold worldwide, with the highest rates reported in North America and Europe. The highest breast cancer incidence rates in Southeast Asia have been reported for the Manila Cancer Registry in the Philippines, with an age‐standardized rate of 47.7 per 100,000 per year. The possible contribution of hereditary factors to these elevated rates has not been investigated. We conducted a case‐control study of 294 unselected incident breast cancer cases and 346 female controls from Manila, Philippines. Cases and controls were selected from women below the age of 65 undergoing evaluation at the PGH in Manila because of a suspicious breast mass. Molecular analysis identified 12 BRCA2 mutations and 3 BRCA1 mutations. We estimate the prevalence of BRCA mutations among unselected breast cancer cases in the Philippines to be 5.1% (95% CI: 2.6–7.6%), with a prevalence of 4.1% (95% CI: 1.8–6.4%) for BRCA2 mutations alone. The BRCA2 4265delCT and 4859delA mutations were found in 2 and 4 unrelated cases, respectively; haplotype analysis confirmed that these, and the BRCA1 5454delC mutation, are founder mutations. BRCA2 mutations were also found in 2 of 346 controls (0.6%; 95% CI: 0.2–1.4%). Compared with non‐carrier cases, the cumulative risk of breast cancer for first‐degree relatives of mutation carriers was 24.3% to age 50, compared with <4% for first‐degree relatives of non‐carrier cases (RR = 6.6; 95% CI: 2.6–17.2; p= 7.5 × 10^−6^). Our data suggest that penetrance of BRCA mutations is not reduced in the Philippines. Germline mutations in the BRCA2 gene contribute more than mutations BRCA1 to breast cancer in the Philippines, due in large part to the presence of 2 common founder mutations. © 2002 Wiley‐Liss, Inc.