Report of the first patient treated for pelvic sarcoma with a directional 103Pd brachytherapy device

Abstract Purpose Durable local control of leiomyosarcoma of the pelvic sidewall is described at 3 years following implantation with a novel low-dose rate (LDR) brachytherapy device that allows directional irradiation of tumor beds while sparing organs at risk. Methods and materials The patient is a 65-year-old African-American male with incidental finding of a left pelvic sidewall mass. While management was initially deferred, the patient became symptomatic. CT imaging indicated enlargement of the pelvic mass measuring 8.1 x 6.4 x 3.7cm with no distant metastasis. Biopsy revealed a grade 2 leiomyosarcoma. Given the locally-advanced disease, the patient underwent preoperative pelvic intensity-modulated radiotherapy (IMRT; 50.4Gy in 28 fractions) followed by surgical resection. Given concerns for R1 surgical margins, an absorbable brachytherapy sheet was implanted intraoperatively in January 2016 with 48 sources containing 103Pd and gold shielding (CivaSheet). The total implanted source strength was 51 U and the exposure rate at 1 m was 0.01 mR/h. Surgical pathology revealed stage IIB (ypT2b, pNx, pMx) leiomyosarcoma grade 2, measuring 8.3x5.8x3cm with necrosis and a focal positive margin. Results Post-implant CT-based dosimetry, with physical dose of 27.8Gy to a 0.5cm depth, delivered a BED=21.7Gy and EQD2=17.5Gy (near the center of the desired EQD2 range). Total EQD2 delivered to the tumor was 67.2Gy. No early or late grade 3+ gastrointestinal or genitourinary toxicities were observed. At 40 months after implantation, clinical evaluation and CT imaging surveillance demonstrated no evidence of tumor recurrence. Conclusions Favorable oncologic outcomes with local disease control were achieved with the use of CivaSheet in a patient with locally-advanced soft-tissue sarcoma, despite a focally positive microscopic margin. This technology may offer durable local control for selected sarcoma cases while sparing critical organs at risk.