Hypofractionated Radiotherapy in Soft Tissue Sarcomas – A Single Center Experience

Radiotherapy (RT) plays an important role in the management of soft tissue sarcoma (STS). Although these tumors have a low alpha/beta ratio, being considered sensitive to RT fraction size, little evidence is available on the safety and efficacy of hypofractionated RT for STSs. We report our initial experience. Twenty-nine patients with newly diagnosed or metastatic sarcomas were treated between February 2013 and January 2020. They received doses of 30-35Gy in 5 fractions, delivered on alternative days over 2 weeks, for an EQD2 of 50-64.2Gy using an alpha/beta ratio of 4. Treatments were planned using IMRT and delivered with image guidance with daily CBCTs. Concomitant systemic therapy was not used. A total of 44 lesions were treated. Twenty-nine received 35Gy and 15 received 30Gy. The most prevalent histologies were liposarcoma (13%) and Ewing’s sarcoma (13%). Five patients received neoadjuvant radiotherapy for oligometastatic or newly diagnosed STS prior to curative surgery, and the remainder were treated with palliative intent for pain and/or radiological disease progression of oligometastatic disease. Overall, RT was well tolerated, with 3 patients presenting pain flare and 6 presenting with dermatitis grade 1 during the month following RT. Three patients presented with grade 1 GI toxicity during treatment and 2 complained of fatigue. Two patients treated to the pelvis and proximal thigh developed radiological and clinical signs of grade 2 myositis that responded well to oral corticosteroids. Of the 7 lesions treated preoperatively, two lesions below the knee developed wound infections and dehiscence post-operatively, while 2 lesions treated in the upper limb and 3 in the thigh had no wound healing issues. With a median follow-up of 9.4 months (0.1-53.3), radiological response or stability of disease was seen in 24 treated lesions, including 2 complete responses, and symptoms improved in 20 of them. Post RT, 22 patients presented with progressive disease and, of those, 4 progressed locally in the previously treated lesions, 13 presented with distant progression and 5 had evidence of both local and distant relapse. A treatment schedule of 30-35Gy delivered in 5 fractions appears to be well tolerated, with mild to moderate side effects and good local control of oligometastatic disease. Higher complication rates in patients who underwent surgery after preoperative hypofractionated RT occurred in below the knee lesions. These hypothesis-generating findings should be taken with caution given the small number of patients and short follow-up. A phase I/II trial for hypofractionated preoperative RT for patients with newly diagnosed STS is underway.