Packed with promise.

Top Line: Preliminary reports of five-fraction pre-op radiation for soft tissue sarcoma have been promising, and now we have larger prospective phase 2 data to bolster the movement.

The Study: Here, 32 patients at the Medical College of Wisconsin received 7 Gy x 5 = 35 Gy delivered every other day to sarcomas of the lower (n=25) / upper (n=5) extremity or trunk (n=2)  4-6 weeks prior to resection. All patients had an MRI-simulation and received treatment with either a 3D or IMRT technique. In keeping with the times, the clinical target volume was tighter than that seen historically with 2 cm longitudinal / 1 cm radial margins on tumors ≤8 cm and 3 / 1.5 cm margins on tumors >8 cm. Anatomic boundaries such as uninvolved bone and muscle compartment that were not abutting the GTV were respected. The planning target volume included another 0.5 cm margin cropped 0.3-0.5 cm from uninvolved skin. Thankfully five-fraction dose constraints are included in the supplement. At a median follow-up of just over 3 years, the primary endpoint of local control was an impressive 100%. A bigger problem proved distant control with a metastasis-free survival of 69% at 3 years, and this didn’t appear influenced by the receipt of chemotherapy as a component of first-line therapy as was the case for 10 enrollees.Secondary endpoints of toxicity were largely in line with prior phase 3 data on conventionally-fractionated pre-op radiation: 25% experienced wound complications, 22% grade 2 fibrosis and 13% grade 3 fibrosis. A final interesting observation was that the four patients who experienced treatment-related necrosis and fibrosis of ≥ 90% at time of surgery were all alive at 3 years compared to 78% of the rest of the cohort.

TBL: Phase 2 data point to only upsides with five-fraction pre-op radiation to 35 Gy for soft tissue sarcoma of the extremity and trunk. | Bedi, Adv Radiat Oncol 2022