Patterns of Failure in High-Grade Soft Tissue Sarcomas of the Extremities and Trunk Wall After Pre- or Postoperative Radiation Therapy

PURPOSE: Radiotherapy (RT) is a mainstay of treatment for high-grade soft tissue sarcomas (STS). We sought to examine the pattern of local recurrence (LR) with regard to target volume, clinical course, and tumor characteristics in extremity and trunk wall STS patients receiving pre- or postoperative RT. METHODS AND MATERIALS: In this retrospective study, LR rates and patterns in 91 adult patients with a primary diagnosis of localized high-grade STS of the extremities and trunk wall treated with pre- or postoperative RT at our institution between 2004 and 2021 were analyzed. Radiation treatment plans and imaging data sets at diagnosis and LR were compared. RESULTS: Seventeen out of 91 (18.7 %) patients developed a LR after a median time of 12.7 months. In 10 out of 13 LRs (76.9%) with available treatment plans and radiographic imaging data at the time of recurrence, the LR occurred within the planned target volume (PTV), 2 LRs were marginal (15.4%, at the edge of the PTV volume), and one relapsed out-of-field (7.7%, outside the PTV volume). Positive surgical margins (microscopic or macroscopic) were found in 5 out of 91 patients (5.5%), 1 of which was found in the 17 patients with LRs (5.9%). Eleven of 13 LR patients (84.6%) with available treatment plans and radiographic imaging data received postoperative RT; the median total RT dose was 60 Gy. Volumetric-modulated arc therapy was used in 10 (76.9%), intensity-modulated RT in 2 (15.4%), and 3-dimensional conformal radiation therapy in 1 (7.7%) of 13 LRs. CONCLUSIONS: The majority of LRs occurred within the PTV suggesting that LR is most likely not a consequence of inadequate target volume definition, but rather of radioresistant tumor biology. To further improve local tumor control, future research on the potential of dose escalation with normal tissue sparing, STS subtype-specific tumor biology, radiosensitivity, and surgical technique is indicated.