Aim: To investigate the association between mammographic breast density (MBD) change and disease free survival in hormone receptor positive breast cancer during anti-estrogen therapy.
Methods: This was a single centre study performed at Royal Perth Hospital. Patients were identified from the hospital breast unit database with hormone receptor positive breast cancer planned for curative treatment between 1994-2011. Demographic, pathology, treatment and outcome data were obtained from the unit database, case notes, clinic letters, electronic radiology and pathology systems and the Western Australian Cancer Registry. Mammograms were obtained from the hospital radiology archives and Breastscreen Western Australia. Film mammograms were scanned to obtain digital images. MBD was read by single reader using Cumulus software. Percentage change in MBD was compared between groups. The mammogram taken at diagnosis and the first mammogram taken in the 9-18 month period post-diagnosis were compared.
Results: A total of 1921 patients were identified. At diagnosis 22% were premenopausal, 8% perimenopausal and 69% postmenopausal. 62% received tamoxifen as initial endocrine therapy, 13% letrozole, 18% anastrazole, and 5% ovarian suppression plus and aromatase inhibitor or tamoxifen. Interim univariate analysis of 921 patients gave a disease free survival hazard ratio of 0.45 (95%CI 0.25-0.8;p=0.006) for those with MBD reduction of >20% relative to those with MBD reduction of <0%. MBD measurement has now been completed on the remaining mammograms and analysis of the full cohort will be presented.
Conclusion: Interim analysis shows that a greater reduction in MBD during anti-estrogen therapy is associated with improved breast cancer outcome. Measurement of MBD change has the potential to allow tailoring of adjuvant endocrine therapy.