This indicates that TGFBR1*6A association with breast cancer risk may have a more modest effect size than in the original reports (regression toward the mean) and these studies were not powered to account for the effects of other confounding/modifying factors apart from ethnicity and geographical location that modify the magnitude of the risk attributable to the TGFBR1*6A polymorphism. This evidence concerns the gene TGFBR1 and breast cancer.