Retrospective analyses of hormone receptors among patients enrolled in the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-24 study showed that women with estrogen receptor (ER)-positive ductal carcinoma in situ (DCIS) who received tamoxifen after standard therapy had significant reductions in subsequent breast cancer. “The use of adjuvant tamoxifen should be considered for patients with DCIS,” concluded the researchers, who represented the NSABP and centers in the United States and the Netherlands.
“The B-24 trial was initiated before hormone receptor status was routinely evaluated in DCIS, and patients were enrolled without this information. The current study was undertaken to evaluate, retrospectively, the relationship between adjuvant tamoxifen and receptor status in DCIS, with the expectation that the results would be similar to those in [invasive breast cancer],” the authors wrote.
For the retrospective evaluation, ER and progesterone receptor (PgR) results were available for a subset of 732 patients, 41% of the original study population. ER was positive in 76% of those patients, and PgR was positive in 66%.
“Patients with ER-positive DCIS treated with tamoxifen (vs placebo) showed significant decreases in subsequent breast cancer at 10 years (HR = 0.49; P = .001) and overall follow-up (HR = 0.60; P = .003), which remained significant in multivariable analysis (overall HR = 0.64; P = .003),” the researchers reported. “Results were similar, but less significant, when subsequent ipsilateral and contralateral, invasive and noninvasive, breast cancers were considered separately.” Stratifying patients by PgR and by PgR and/or ER status was not more predictive than ER alone.
“Tamoxifen reduced contralateral breast cancer in patients with ER-positive and ‑negative DCIS, as expected (ie, prevention),” the authors noted. “No ipsilateral benefit was observed in ER-negative disease, emphasizing that tamoxifen must bind to functional ER to exert its beneficial effect on preexisting residual tumor cells.”
The study was supported by grants from the National Institutes of Health and by the Breast Research Foundation and AstraZeneca. ■
Allred DC, et al: J Clin Oncol. March 12, 2012 (early release online).