(ChemotherapyAdvisor) – Women in the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-24 study with estrogen receptor(ER)-positive ductal carcinoma in situ (DCIS) who received adjuvant tamoxifen after standard therapy had a significant reduction in subsequent breast cancer, according to a retrospective study published in the Journal of Clinical Oncology online March 5.

“Although an ASCO 2007 update of recommendations for the use of tumor markers in breast cancer concluded that available data were insufficient to support using ER status of DCIS in making decisions about tamoxifen treatment, we believe it is time to revise this recommendation to allow all patients with DCIS to have ER and PgR measured for a tailored treatment approach,” a separate article published in the same issue stated.

Previously, NSABP B-24 observed a significant benefit with adjuvant tamoxifen in patients with DCIS following lumpectomy and radiation; however, women were not stratified by hormone-receptor status at enrollment. This study evaluated ER and progesterone receptors (PgR) in 732 patients with DCIS, 41% of the original population, primarily by immunohistochemistry using comprehensively validated assays. Benefit of tamoxifen by receptor status was evaluated at 10 years and at overall follow-up, a median of 14.5 years.

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Of patients with DCIS, ER was positive in 76%, and those treated with tamoxifen showed significant decreases in subsequent breast cancer at 10 years (HR, 0.49; P <0.001) and overall follow-up (HR, 0.60; P=0.003) compared with placebo, which remained significant in multivariable analysis (overall HR, 0.64; P=0.003).

“Results were similar, but less significant, when subsequent ipsilateral and contralateral, invasive and noninvasive, breast cancers were considered separately,” the investigators noted. No significant benefit was observed in ER-negative DCIS. PgR was positive in 66% of patients and either receptor in 79%; however, neither was more predictive than ER alone.

These results mandate that physicians discuss endocrine therapy as an alternate method of risk reduction in women with ER-positive DCIS,” an accompanying editorial notes, noting that since this trial was conducted, “other options are available to postmenopausal women with DCIS who wish to minimize their risk of future breast cancer events.”