What Is the Prognostic Value of the Pathologic Response after Neoadjuvant Radiotherapy in Soft Tissue Sarcoma? An Institutional Study Using the EORTC-STBSG Response Score

Abstract

Background/Objectives: The relationship between pathologic findings in soft tissue sarcoma (STS) after neoadjuvant treatment and oncological outcomes remains uncertain due to varying evaluation methods and cut-off values. This study aims to assess pathologic findings after neoadjuvant radiotherapy in STS using the EORTC-STBSG response score and evaluate its prognostic value. Methods: Clinical and outcome data from 44 patients were reviewed. Resected specimens were re-evaluated to measure viable cells, necrosis, fibrosis, and hyalinization. Local recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), and overall survival (OS) were analyzed using Kaplan-Meier survival analysis. Cox proportional hazards regression was used for univariate and multivariate analyses to correlate outcomes with pathologic response. Results: The median percentages of viable cells, necrosis, and fibrosis/hyalinization were 20%, 11%, and 40%, respectively. A pathologic complete response (pCR), defined as ≤5% viable cells, was achieved in 25% of cases. Local recurrence occurred in 33% of cases, with a significantly higher rate of 64% after R1 resection compared to 22% after R0 resection. Distant metastases were observed in 42% of patients, primarily in the lungs. The 3-year rates for LRFS, DMFS, and OS were 65%, 54%, and 67%, respectively. A correlation between outcomes and tumor size, grade and histological subtype was observed. Classifying pathologic response by the EORTC-STBSG score failed to show an association with outcomes. Patients achieving pCR showed lower risk of LR and improved OS. Conclusions: While the EORTC-STBSG score did not show a prognostic value, resection specimens with ≤5% viable cells were linked to improved LRFS and OS.

Keywords: EORTC response score; neoadjuvant radiotherapy; pathologic response; preoperative radiotherapy; soft tissue sarcoma.

Figure 1

Representative figures from the different EORTC–STBSG grades corresponding to the outcome of radiotherapy (eosin–hematoxylin stain, 200× original magnification). (A) collagenous stroma with complete absence of neoplastic cells, (B) only scattered, single viable cells into a necrotic and collagenous stroma, (C) tumor cells interspersed throughout the stroma, occupying less than 10% of the area, (D) tumor cells can be easily identified, with a diffuse growth pattern occupying less than 50% of the area and (E) poor response to radiotherapy showing increased population of viable tumor cells occupying more than 50% of the area.

Figure 2

Kaplan–Meier curves for local recurrence free survival (LRFS), distance metastasis free survival (DMFS) and overall survival (OS) of the studied patient population.