On the Feasibility of Treating to a 1.5 cm PTV for Accelerated Partial Breast Brachytherapy With a Commercial Single Entry Hybrid Applicator

Abstract

Purpose: It’s well known that mediastinum, lungs, heart, spinal cord are the unwishful targets in distant radiation therapy at the parasternal zone in breast cancer patients. Different treatment-related morbidity has been observed. That was the reason for the modern radiation therapy application at this zone. It has been shown that internal mammary artery is the optimal natural pathway for the radiation sources which leads to symmetrical irradiation of internal mammary lymph nodes. Our goal was to identify the efficacy of breast cancer treatment depending on the parasternal brachytherapy using Co or Cf sources in comparison with Ir afterloading and to analyze long-term results in each group. Materials and Methods: 868 patients with central and medial location of the tumor underwent parasternal brachytherapy. In 575 women (66.2%) 60Co was used, in 194 (22.4%) 252Cf was used, and 99 (11,4%) had afterloading ‘‘Microselectron-HDR’’ irradiation with 192Ir. Medium age was 48.2 ( 15.8) years in the first group, 50.8 ( 12.6) years in the second group, and 49.7 ( 9.8) years in the third group. I stage had 98 patients (11.3%), IIA e 388 (44.7%), IIB e 202 (23,3%), IIIA e 121 (13.9%), IIIB e 59 (6.8). All women with T3 and T4 (62 e 19.8%) had standard preoperative chemotherapy. Manual installation of 60Co or 252Cf sources was performed for the time necessary for the prescribed dose to be achieved. The isodose at the specification point was 80 Gy, while at 2 cm from the medial field edge total dose was at least 36 Gy. A total dose of 45 Gy in three 15 Gy fractions was delivered to the internalmammary lymph nodes using 192Ir afterloading. Results:With a median followup of 148 months no significant difference in 15-year disease-free and overall survival was detected in all brachytherapy techniques. No significant complications associated with brachytherapy were registered. Conclusions: Ir afterloading technique we conceder to be preferable to manual Co and Cf radiation source installation due to decreased medical staff irradiation. It has become apparent that distant radiation therapy is a cause of significant morbidity, especially among long-term survivors. If the internal mammary nodes are to be treated we suggest using afterloading brachytherapy technique.