Histologic Appearance After Preoperative Radiation Therapy for Soft Tissue Sarcoma: Assessment of the European Organization for Research and Treatment of Cancer–Soft Tissue and Bone Sarcoma Group Response Score

• DOI: 10.1016/j.ijrobp.2017.02.087
• Publication Date: 2017-02-24T08:16:30Z
• Authors: Inga-Marie Schaefer; Jason L. Hornick; Constance M. Bary...; Chandrajit P. Raut; Sagar A. Patel; Trevor J. Royce; Christopher D.M. ...; Elizabeth H. Baldini
• Keywords: Adult; Aged, 80 and over; Leiomyosarcoma; Male; Neoplasm, Residual; Cell Survival; Fibrosarcoma; Sarcoma; Kaplan-Meier Estimate; Liposarcoma; Middle Aged; Fibrosis; Disease-Free Survival; 3. Good health; Necrosis; 03 medical and health sciences; 0302 clinical medicine; Infarction; Humans; Female; Aged; Follow-Up Studies; Proportional Hazards Models

To critically assess the prognostic value of the European Organization for Research and Treatment of Cancer-Soft Tissue and Bone Sarcoma Group (EORTC-STBSG) response score and define histologic appearance after preoperative radiation therapy (RT) for soft tissue sarcoma (STS).For a cohort of 100 patients with STS of the extremity/trunk treated at our institution with preoperative RT followed by resection, 2 expert sarcoma pathologists evaluated the resected specimens for percent residual viable cells, necrosis, hyalinization/fibrosis, and infarction. The EORTC response score and other predictors of recurrence-free survival (RFS) and overall survival (OS) were assessed by Kaplan-Meier and proportional hazard models.Median tumor size was 7.5 cm; 92% were intermediate or high grade. Most common histologies were unclassified sarcoma (34%) and myxofibrosarcoma (25%). Median follow-up was 60 months. The 5-year local recurrence rate was 5%, 5-year RFS was 68%, and 5-year OS was 75%. Distribution of cases according to EORTC response score tiers was as follows: no residual viable tumor for 9 cases (9% pathologic complete response); <1% viable tumor for 0, ≥1% to <10% for 9, ≥10% to <50% for 44, and ≥50% for 38. There was no association between EORTC-STBSG response score and RFS or OS. Conversely, hyalinization/fibrosis was a significant independent favorable predictor for RFS (hazard ratio 0.49, P=.007) and OS (hazard ratio 0.36, P=.02).Histologic evaluation after preoperative RT for STS showed a 9% pathologic complete response rate. The EORTC-STBSG response score and percent viable cells were not prognostic. Hyalinization/fibrosis was associated with favorable outcome, and if validated, may become a valid endpoint for neoadjuvant trials.