Interstitial brachytherapy alone after breast conserving surgery: Interim results of a German-Austrian multicenter phase II trial

Purpose To evaluate the value of interstitial brachytherapy (iBT) alone in the treatment of low-risk breast cancer patients with regard to local control, side effects, and cosmesis. Methods and materials From November 2000 to January 2004, 176 patients with low-risk breast cancer were treated with iBT only. Patients were eligible for entering the study if: the tumor size was <3 cm; resection margins were clear by at least 2 mm; there were no lymph node metastases or only one micrometastasis (pNo, pNmi); age was >35 years; steroid hormone receptor was positive; and histologic grade was 1 or 2. Seventy-five percent of patients received pulsed-dose-rate brachytherapy (Dref = 50 Gy); 25% of patients received high-dose-rate brachytherapy (Dref = 32.0 Gy). An interim analysis is presented for all patients after an interim follow-up of 12 months, and for half the patient population with an interim follow-up of 21 months. Results All patients remained disease-free on the date of analysis. A perioperative complication breast infection was recorded for 1/176 (0.6%) patients. Late toxicity i.e., hypersensation, hyperpigmentation, fibrosis, or teleangiectasia was observed in 1–12% of all patients. Grade I Fibrosis was registered in 7.6% (13/172) and grade II in 7.0% (12/172) of evaluable patients. Similarly, grade I teleangiectasia was observed in 4.7% (8/172), grade II in 0.6% (1/172), and grade III also in 0.6% (1/172) of evaluable patients. Excellent or good cosmetic results have been observed in 92–95% of patients. Conclusions Brachytherapy as monotherapy in low-risk breast cancer patients after breast-conserving surgery is an effective, precise treatment modality without perioperative morbidity, low acute, mild late toxicity, and yields good to excellent cosmetic results.