Sole brachytherapy of the tumor bed after conservative surgery for T1 breast cancer: Five‐year results of a phase I–II study and initial findings of a randomized phase III trial

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Abstract
Background and Objectives The objectives of this study were to test the feasibility of sole interstitial high‐dose‐rate brachytherapy (HDR‐BT) after breast‐conserving surgery (BCS) for T1 breast cancer in a phase I–II study, and to present the initial findings of a phase III trial comparing the efficacy of tumor bed radiotherapy (TBRT) alone with conventional whole breast radiotherapy (WBRT). Methods Forty‐five prospectively selected patients with T1 breast cancer undergoing BCS were enrolled into a phase I–II study of TBRT alone, using interstitial HDR implants. HDR‐BT of 7 × 4.33 Gy (n = 8) and 7 × 5.2 Gy (n = 37) was delivered to the tumor bed. Based on the results of this phase I–II study, a further 126 patients were randomized to receive 50 Gy WBRT (n = 63) or TBRT alone (n = 63); the latter consisted of either 7 × 5.2 Gy HDR‐BT (n = 46) or 50‐Gy wide‐field electron irradiation (n = 17). Breast cancer related events and side effects were assessed. Results In the phase I–II study, at a median follow‐up of 57 months, 2 (4.4%) local, 3 (6.7%) axillary, and 3 (6.7%) distant failures were observed. Two patients (4.4%) died of breast cancer. The 5‐year probability of cancer‐specific, relapse‐free and local recurrence‐free survival was 90.0%, 85.9%, and 95.6%, respectively. The cosmetic results were judged to be excellent in 44 of 45 patients (97.8%). Severe (higher than grade 2) skin sequelae or fibrosis was not found. Symptomatic fat necrosis occurred in one patient (2.2%). In the phase III study, at a median follow‐up of 30 months, the locoregional tumor control was 100% in both arms. The 3‐year probability of cancer‐specific and relapse‐free survival was 98.1% and 98.4% in the WBRT group and 100% and 94.4% in the TBRT group, respectively (P = NS). There was no significant difference between the two treatment arms regarding the incidence of radiation side effects. Conclusions Five‐year results of our phase I–II study prove that sole HDR‐BT of the tumor bed with careful patient selection and adequate quality assurance is a feasible alternative to WBRT. However, long‐term results of phase III trials are required to determine the equivalence of TBRT alone, compared with WBRT in the management of selected patients with early breast cancer. J. Surg. Oncol. 2002;80:121–128.