Comparison of histological response across patients with Ewing sarcoma treated with preoperative chemotherapy with or without preoperative radiotherapy

Purpose: This study aimed to compare the histological response, a surrogate preoperative treatment efficacy marker, of patients treated with preoperative chemotherapy with or without preoperative radiotherapy. Moreover, local recurrence in both groups was investigated. Methods: Surgical specimens from 210 patients with Ewing sarcoma were assessed between 2003 and 2020 to evaluate their histological response to preoperative treatment; 181 patients received preoperative chemotherapy, while 29 received both preoperative chemotherapy and radiotherapy. The histological response rate in the surgical section was assessed based on tumour necrosis and reparative fibrous tissue. Results: The median histological response rates were 100% (interquartile range = 83–100%) for the preoperative chemotherapy and radiotherapy group and 90% (interquartile range = 60–100%) for the preoperative chemotherapy group (P = 0.004). Multivariate logistic regression analysis indicated that the administration of the preoperative radiotherapy (Odds ratio = 3.36 [95% confidence interval, CI 1.32–8.54]; P = 0.011) and small tumour volume (< 200 mL) were associated with the achievement of > 95% histological response (Odds ratio = 0.52 [95% CI 0.27–0.99]; P = 0.047). Local recurrence occurred in 9.9% (18/181) of patients who received preoperative chemotherapy and in 2.4% (1/29) of patients who received both preoperative chemotherapy and radiotherapy (P = 0.258). Conclusion: Preoperative radiotherapy might enhance histological response, potentially reducing local recurrence. Therefore, it should be considered for patients with Ewing sarcoma who are at high risk of local recurrence or may have inadequate surgical margins.