Histologic Appearance Following Pre-operative Radiation Therapy for Soft Tissue Sarcoma: Assessment of the EORTC-STBSG Response Score

Publication date: Available online 24 February 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Inga-Marie Schaefer, Jason L. Hornick, Constance M. Barysauskas, Chandrajit P. Raut, Sagar A. Patel, Trevor J. Royce, Christopher D.M. Fletcher, Elizabeth H. Baldini
PurposeHistologic appearance defined as percent necrosis following neoadjuvant therapy predicts outcome in osteosarcoma, but has not been systematically studied in soft tissue sarcoma (STS). The EORTC-STBSG has proposed a response score following neo-adjuvant radiation therapy (RT) or chemotherapy for STS based on five tiers of percent residual viable cells (1). We sought to critically assess the prognostic value of the EORTC-STBSG response score and define histologic appearance following pre-operative RT for STS.Methods and MaterialsFor a cohort of 100 patients with STS of the extremity/trunk treated at our institution with pre-operative RT followed by resection, two 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.ResultsMedian 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. Five-year LR rate was 5%, 5-year RFS was 68%, and 5-year OS 75%. Distribution of cases according to EORTC response score tiers was: no residual viable tumor for 9 cases (9% pathologic complete response); < 1% viable tumor for 0, > 1% - < 10% for 9, >10% - <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, (HR 0.49, P = 0.007) and OS (HR 0.36, P = 0.02).ConclusionHistologic evaluation after pre-operative 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.

Teaser

Histologic treatment response predicts outcome in osteosarcoma, but has not been systematically studied in soft tissue sarcoma. EORTC-STBSG proposed a neoadjuvant response score based on five tiers of percent residual viable cells. We assessed histologic appearance after pre-operative radiation for 100 soft tissue sarcomas of extremity/trunk and found the EORTC response score was not prognostic. Whereas, extent of hyalinization/fibrosis was associated with favorable outcome, and if validated, may become a valid endpoint for neoadjuvant trials.


http://ift.tt/2ligVxg