SU‐GG‐T‐46: Dose Volume Analysis of HDR Breast Brachytherapy Plan

Purpose: To report dose volume analysis for HDR interstitial breast brachytherapy.Method and Materials: The interstitial HDR brachytherapy is performed on localized breast carcinoma patients using a custom made template. The catheters were implanted using the template to cover surgical resection with 1.5cm margin. A custom made template, with adjacent grids forming a triangle with 1cm spacing along base and 1 cm along vertical. The design goal was to obtain uniform coverage around PTV and to minimize dose gradient inside volume. The treatment was delivered for 34Gy in 10 fractions over 5 days. Four criteria were used for plan evaluation. The PTV must encompass with reference dose (RD) from 0.95 to 1.0 × RD, ⩽ 30% of PTV must encompass with 1.5×RD, ⩽ 10% of PTV must encompass 2×RD and the skindose must be kept < 0.75×RD. We have recorded the volume of lung and hearttissue covering 10% of the RD. Also we have measured the skindose on inferior and superior implant planes. Results: The coverage was in the range of 96 to 100% (N=80) at a median value of 98%. The % of PTV coverage for 1.5RD was in the range of 7 to 32 (N=80) at median value of 28, 3 patients exceeded the 30% criteria. The % of PTV for 2×RD was in the range of 4.5 to 16 at median value of 12 with 8 patients exceeding 10% criteria. The measuredskindose ranged from 25 to 87% of RD at a median value of 74%, with 3 patients (N=80) exceeding the 0.75 RD criteria. Conclusion: The patients tolerated the treatment very well and there were no complications of skin reaction or fat tissue necrosis observed in the series of patients treated with modified template.