In premenopausal breast cancer patients, a change in mammographic breast density strongly suggests the effectiveness of tamoxifen.
Mammographic Density as a Biosensor of Tamoxifen Effectiveness in Adjuvant Endocrine Treatment of Breast Cancer: Opportunities and Implications
Authors: Mullooly M, Pfeiffer RM, et. al.
Tamoxifen is associated with improved breast cancer-specific survival and decreased disease recurrence. There is a subset of women who do not properly metabolize the medication and therefore may not receive all of its health benefits. A measure of tamoxifen metabolism for each woman would be extremely useful: women who are not metabolizing the drug fully may be advised towards a different therapy, and women who are fully metabolizing the drug may easily feel motivated to continue the medication for the full 5-10 year prescription.
The investigators on this study first reviewed prior analyses of breast cancer-specific mortality among premenopausal women treated with tamoxifen. Women whose mammographic breast density declined after beginning the medication had reduced risks of cancer disease recurrence and disease-specific death.
The group then analyzed outcomes among their own premenopausal patients who were treated with tamoxifen as part of their breast cancer therapy. Women who had the highest reduction in mammographic density after one year of tamoxifen therapy were least likely to die of breast cancer. They noted that patients whose density declined by at least 10% a year after starting the medication had improved disease-free survival at five years of follow up (this improvement did not reach statistical significance).
Breast density may be a true causative factor in breast cancer development or it may be a marker for the process. Using all of the reviewed data, it was concluded that evaluating premenopausal women for change in mammographic density after the start of tamoxifen therapy may identify patients with a better prognosis with the medication.