Endocrine therapy use in patients with ductal carcinoma in situ treated with conserving surgery plus radiotherapy was associated with improved event-free survival, thereby confirming the generalizability of the 1999 National Surgical Adjuvant Breast and Bowel Project (NSABP)-B24 trial, a population-based analysis published online ahead of print in the journal Annals of Oncology has shown.
The NSABP-B24 trial showed that tamoxifen decreased the risk of relapse in women with ductal carcinoma in-situ treated with breast conserving surgery and radiotherapy, but a subgroup analysis demonstrated that tamoxifen mostly benefited those with estrogen receptor-positive disease.
For this population-based analysis, researchers identified 417 patients who underwent surgery and radiotherapy before the NSABP-B24 study and 1,548 who underwent the same treatment after the study, who were further divided into those who received treatment before or after the subgroup analysis.
Results showed that 20% of the 2,061 patients received endocrine therapy. Researchers found that the proportion of patients who received endocrine therapy increased from 0.2% before the NSABP-B24 trial to 26% after the trial.
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The study also demonstrated that estrogen receptor-positive disease and younger age were associated with increased use of endocrine therapy, and endocrine therapy was associated with improved event-free survival (HR = 0.6; P=0.02).
The findings suggest that the results of the NSABP-B24 trial are generalizable at a population level.