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Owen D.,Radiation Therapy Program | Tyldesley S.,Radiation Therapy Program | Tyldesley S.,University of British Columbia | Alexander C.,University of British Columbia | And 7 more authors.
International Journal of Radiation Oncology Biology Physics | Year: 2013

Purpose: To examine, in a large, population-based cohort of women, the risk factors for recurrence after mastectomy for pure ductal carcinoma in situ (DCIS) and to identify which patients may benefit from postmastectomy radiation therapy. Methods and Materials: Data were analyzed for 637 subjects with pure DCIS, diagnosed between January 1990 and December 1999, treated initially with mastectomy. Locoregional relapse (LRR), breast cancer-specific survival, and overall survival were described using the Kaplan-Meier method. Reported risk factors for LRR (age, margins, size, Van Nuys Prognostic Index, grade, necrosis, and histologic subtype) were analyzed by univariate (log-rank) and multivariate (Cox modeling) methods. Results: Median follow-up was 12.0 years. Characteristics of the cohort were median age 55 years, 8.6% aged ≤40 years, 30.5% tumors >4 cm, 42.5% grade 3 histology, 37.7% multifocal disease, and 4.9% positive margins. At 10 years, LRR was 1.0%, breast cancer-specific survival was 98.0%, and overall survival was 90.3%. All recurrences (n=12) involved ipsilateral chest wall disease, with the majority being invasive disease (11 of 12). None of the 12 patients with recurrence died of breast cancer; all were successfully salvaged (median follow-up of 4.4 years). Ten-year LRR was higher with age ≤40 years (7.5% vs 1.5%; P=.003). Conclusion: Mastectomy provides excellent locoregional control for DCIS. Routine use of postmastectomy radiation therapy is not justified. Young age (≤40 years) predicts slightly higher LRR, but possibly owing to the small number of cases with multiple risk factors for relapse, a subgroup with a high risk of LRR (ie, approximately 15%) was not identified. © 2013 Elsevier Inc. All rights reserved.

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