What is the benefit of using IMRT for extremity soft tissue sarcoma? Two phase 2 trials have investigated IMRT in the preoperative setting for STS. IMRiS was a prospective, phase 2 trial from the UK, and with 168 patients it is the largest IMRT trial to date for STS. It included patients receiving either preop (67%) or postop (33%) RT. Preop RT consisted of 50 Gy in 25 fractions. Postop patients with negative margins received 60 Gy and 52.2 Gy in 30 fractions using a simultaneous integrated boost technique. Those with positive margins received 66 Gy and 53.46 Gy in 33 fractions. A longitudinal strip of skin and soft tissue was limited to a V20 <50%. Weight-bearing bone within the treatment field was limited to V50 <50%. The whole bone mean dose was limited to ≤40 Gy, and the V40 was limited to ≤64%. The primary endpoint of grade 2+ fibrosis at 24 months was 10.8% (11% preop, 10.5% postop). This is comparable to the rates of moderate fibrosis seen in other IMRT trials, and it was lower than the historical control rate of 28%. The rates of wound complication were 29.2% in preop patients and 3.8% in postop patients. | Seddon, Int J Radiat Oncol Biol Phys 2024
