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.
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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.
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