Purpose: The aim of this study was to evaluate effect, toxicity, and cosmesis of a prospectively applied pulsed dose rate (PDR) brachytherapy boost schedule in patients with stage I/II/IIIa invasive breast cancer.
Patients and methods: A total of 113 patients were treated after breast-conserving surgery (BCS) and external beam radiotherapy (median 50 Gy, range 46-52). The boost dose was graded in accordance to the pathologic tumor characteristics: 20-25 Gy: incomplete resection (n = 34), vascular invasion (n = 27), close margin resection (n = 41); 15 Gy: T2G3 stage (n = 11). PDR brachytherapy (37 GBq, (192)Ir source) was carried out after geometric volume optimization with 1 Gy/pulse/h. The implantation and dose specification were performed similar to the rules of the Paris system.
Results: The overall local failure rate after a median follow-up of 61 months was 4.4% (5/113). The actuarial 5- and 8-year local recurrence-free survival rates were 95% and 93%, respectively. Cosmesis was rated by 90% of the patients as excellent or good. 14/113 patients experienced grade III (all caused by planar telangiectasia) and none of the patients grade IV late toxicity of the skin (RTOG/EORTC). A boost dose of 25 Gy resulted in a significantly higher rate of late toxicity (Fisher's exact test, p < 0.01).
Conclusions: PDR brachytherapy is safe, effective, and provides good cosmesis. A CLDR breast boost can be replaced by PDR brachytherapy without significant loss of therapeutic ratio.