Intrapelvic dose of radiotherapy for breast cancer after breast-conserving surgery

Recently, young patients with breast cancer are increasingly more able to become pregnant in the future in Japan. The purpose of this study was to analyze the exposure dose of intrapelvic organs in patients with breast cancer who received radiotherapy to the breast region after breast-conserving therapy. From July 2003 to June 2004, 14 patients with breast cancer- all had breast-conserving surgery and whole breast radiotherapy following surgery. The radiation dose to the whole breast was 50 Gy in 5 weeks with 2 Gy daily fractions, using 4 MV X-ray 10 Gy and a boost dose was administered to the tumor bed, using a 6 MeV electron beam. At the same time, the radiation dose at the patient's surface was measured using glass rod detectors (GRDs). In much the same way, the surface dose and intra pelvic dose of a rand-phantom were measured. Average intrapelvic dose of the rand-phantom was 2.07 mGy for 2 Gy radiation for the breast of the rand-phantom. The average surface dose in the pelvic region of the rand-phantom was 9.47 mGy for 2 Gy radiation for the breast of the rand-phantom. Therefore, intrapelvic dose is 0.218 times as much as the surface dose in the pelvic region. Estimated intra pelvic dose is 1.2 mGy, according to his conversion factor for 2 Gy radiation for the breast. For radiotherapy of 50 Gy for the breast, the intrapelvic dose is estimated to be about 30 mGy. Radiotherapy after breast-conserving surgery should not be avoided unreasonably to treat a patient who is able to become pregnant. (author)