2.4. Outcome Measurements
The primary outcome in this trial was change in mammographic density (MD) over the study period. Mammography was conducted at enrolment and at Month 12 at the study site, using a single full-field digital mammography machine (Hologic Selenia Mammography System, Hologic Inc., Marlborough, MA, USA). MD was estimated from processed digital mammogram images using Stratus, a fully-automated software that is described elsewhere [To ease comparison to the published literature, we also calculated absolute and relative MD change using dense volume estimates from a commonly used mammographic density measurement software (Volpara