Mammographic patterns as a predictive biomarker of breast cancer risk: Effect of tamoxifen

Mammographic breast density has been shown to be associated with up to a 4- to 6-fold increase in risk of breast cancer, whereas tamoxifen therapy inc reases disease-free survival and reduces mortality. We have therefore inves tigated whether these effects are related. To determine the effects of tamo xifen on mammographic density, mammograms from 94 women who had received ta moxifen for breast cancer and 188 women (without breast cancer) who had not received tamoxifen were visually classified according to the criteria of W olfe, Two controls were age-matched to each case, All of the women were pos tmenopausal (ages, 50-64 years), neither group was taking hormone replaceme nt therapy, and none of the cases had received chemotherapy, There were sig nificant differences in breast density between cases and controls at the in itial mammogram (P = 0.0001) but no significant differences at the follow-u p mammogram (P = 0.51), A significant change to a more lucent pattern had o ccurred among the case group (P = 0.0001), The odds ratio for cancer that w as associated with the more dense (P2 and DY) patterns with respect to the more lucent (N1 and P1) patterns was 3.6 (95% confidence interval, 2.11-6.1 8) at the initial mammogram, This was significantly reduced to 1.5 (95% con fidence interval, 1.32-1.70) after treatment with tamoxifen (P = 0.019; chi (2) = 5.52). The substantial reduction in breast density with tamoxifen pro vides evidence that tamoxifen has the capacity to favorably alter postmenop ausal breast density toward a more lucent pattern, which is associated with reduced risk of breast cancer. Mammographic pattern is, thus, a potential biomarker of breast cancer risk.