Locally advanced high-grade extremity soft tissue sarcoma: Response with novel approach to neoadjuvant chemoradiation using induction spatially fractionated GRID radiotherapy (SFGRT).

Abstract

10575 Background: Improved local control and survival has been observed with increasing rate of tumor necrosis >90% with preoperative chemo-radiation for STS. However the rate of necrosis (90%+) following pre-operative chemo radiation remains low (<50%) and likely even less for locally advanced (>8 cm) tumors. The purpose of this study was to increase the rate of tumor necrosis following preoperative chemo-radiation in the management of soft tissue sarcomas (STS) using induction SFGRT. Methods: Fourteen patients with locally advanced extremity STS ranging in size from 8 cm to 26 cm (median 11.5 cm) were treated with high dose megavoltage radiation using an SFGRT technique. Single dose of induction SFGRT 18 Gy was delivered using 6 MV photons followed by external beam radiation 50 Gy combined with iphosfamide 2 gm/m2/day x 3 and mesna 2 gm/day x 3 in divided doses every three weeks followed by surgery 4-6 weeks after completing neoadjuvant therapy. Results: 12 patients completed the planned treatment. 1 patient had treatment interrupted due to Grade 3 skin reaction and 1 patient underwent an amputation of the foot mid treatment. Follow up ranges from 3 months to 43 months (median 14 mo). 13/14 patients underwent limb salvage surgery with 12 having negative margins. 2 patients have had delayed wound healing. 9/14 (65%) patients had > 90 % tumor necrosis with 2 patients having a pathological complete response. 2 additional patients have had greater than 80% necrosis. There have been no local recurrences and 12 patients are alive with no evidence of disease. Conclusions: The combined use of induction SFGRT and external beam radiation/chemotherapy is an effective way to enhance the necrosis and response to neoadjuvant chemo-radiation and potentially improve local control/ limb salvage and survival in locally advanced extremity STS.