Abstract
Todetermine the associated toxicity, tolerance, and safety of partial-breast reirradiation. Eligibility criteria included in-breast recurrence occurring >1year after whole-breast irradiation, <3cm, unifocal, and resected with negative margins. Partial-breast reirradiation was targeted to the surgical cavity plus 1.5cm; a prescription dose of 45Gy in 1.5Gy twice daily for 30 treatments was used. The primary objective was to evaluate the rate of grade ≥3 treatment-related skin, fibrosis, and/or breast pain adverse events (AEs), occurring ≤1year from re-treatment completion. A rate of ≥13% for these AEs in a cohort of 55 patients was determined to be unacceptable (86% power, 1-sided α=0.07). Between 2010 and 2013, 65 patients were accrued, and the first 55 eligible and with 1year follow-up were analyzed. Median age was 68years. Twenty-two patients had ductal carcinoma in situ, and 33 had invasive disease: 19≤1cm, 13>1 to ≤2cm, and 1>2cm. All patients were clinically node negative. Systemic therapy was delivered in 51%. All treatment plans underwent quality review for contouring accuracy and dosimetric compliance. All treatment plans scored acceptable for tumor volume contouring and tumor volume dose-volume analysis. Only 4 (7%) scored unacceptable for organs at risk contouring and organs at risk dose-volume analysis. Treatment-related skin, fibrosis, and/or breast pain AEs were recorded as grade 1 in 64% and grade 2 in 7%, with only 1 (<2%) grade ≥3 and identified as grade 3 fibrosis of deep connective tissue. Partial-breast reirradiation with 3-dimensional conformal radiation therapy after second lumpectomy for patients experiencing in-breast failures after whole-breast irradiation is safe and feasible, with acceptable treatment quality achieved. Skin, fibrosis, and breast pain toxicity was acceptable, and grade 3 toxicity was rare.
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