XXXX -induced reduction in mammographic density and @entity0 risk reduction: a nested case-control study.

@entity1 @entity440 @entity0
BACKGROUND: Mammographic breast density is a strong risk factor for @entity0 . @entity440 , which reduces the risk of @entity0 in @entity1 at high risk, also reduces mammographic breast density. However, it is not known if @entity440 -induced reductions in breast density can be used to identify @entity1 who will benefit the most from prophylactic treatment with this drug. METHODS: We conducted a nested case-control study within the first International @entity0 Intervention Study, a randomized prevention trial of @entity440 vs placebo. Mammographic breast density was assessed visually and expressed as a percentage of the total breast area in 5% increments. Case subjects were 123 @entity1 diagnosed with @entity0 at or after their first follow-up mammogram, which took place 12-18 months after trial entry, and control subjects were 942 @entity1 without @entity0 . Multivariable logistic regression was used to adjust for other risk factors. All statistical tests were two-sided. RESULTS: In the @entity440 arm, 46% of @entity1 had a 10% or greater reduction in breast density at their 12- to 18-month mammogram. Compared with all @entity1 in the placebo group, @entity1 in the @entity440 group who experienced a 10% or greater reduction in breast density had 63% reduction in @entity0 risk (odds ratio = 0.37, 95% confidence interval = 0.20 to 0.69, P = .002), whereas those who took @entity440 but experienced less than a 10% reduction in breast density had no risk reduction (odds ratio = 1.13, 95% confidence interval = 0.72 to 1.77, P = .60). In the placebo arm, there was no statistically significant difference in @entity0 risk between subjects who experienced less than a 10% reduction in mammographic density and subjects who experienced a greater reduction. CONCLUSION: The 12- to 18-month change in mammographic breast density is an excellent predictor of response to @entity440 in the preventive setting.
