Progesterone receptor gene polymorphism is associated with decreased risk for breast cancer by age 50

In a population-based case-control study for breast cancer before the age o f 51 years, 554 cases and 559 age-matched controls were genotyped for the p olymorphic progesterone receptor allele PROGINS. Breast cancer risk was dec reased in women carrying the PROGINS allele, The odds ratio adjusted for ag e and study region was 0.76 [95% confidence interval (CI), 0.58-1.00]. Comp ared with wild-type A1/A1 homozygotes, the odds ratio for A1/A2 heterozygot es and A2/A2 homozygotes was 0.82 (95% CI, 0.62-1.08) and 0.27 (95% CI, 0.1 0-0.74), respectively, suggesting a gene dosage effect of the A2 allele. Th ere was suggestive evidence for a differential effect by menopausal status (P = 0.07) and by family history of breast cancer (P = 0.15).