RADT-02. INTRAOPERATIVE RADIOTHERAPY IN BRAIN METASTASIS SURGERY RESULTS IN LESS RADIONECROSIS THAN FSRS WITH EQUAL ONCOLOGICAL OUTCOME

Abstract PURPOSE/OBJECTIVE Aim of this study is to compare time parameters of treatment as well as outcome, local control and the rate of radionecrosis (RN) in patients that underwent resection of BM with adjuvant fSRS compared with ioRT in a single center setting. MATERIAL/METHODS We performed a retrospective single center analysis comparing patients receiving either fSRS after BM resection or ioRT between 2013 and 2021 in University Augsburg Medical Center with respect to RN, overall survival and local control. Time point of analyis was 15.10.2023. Treatment protocolls: RESULTS We analyzed 129 patients receiving 137 radiation treatments of a resection cavity (fSRS:72/75; ioRT:57/62). Median FU was 8 months. Both groups did not show significant differences regarding age, RPA class, size and number of mets. Median Paddick Conformity Index of the fSRS treatment plans was 0.73 (0.29-0.91). Surgery was prolonged by mn. 25min. in the ioRT group (fSRS:137 min. [66-137] vs. ioRT:162min.[89-308]). Length of hospitalization was mdn. 8d[3-41] in the fSRS vs. 7[2-41] in the ioRT group. 1-year overall survival (fSRS: 60.1% (95%CI 47.0-70.9%) vs ioRT: 58.5% (95%CI 43.9-70.5%) p=0.415), local control (fSRS: 89.0% (95% CI 75.2-95.4%) vs. ioRT: 86.8% (95% CI 71.0-94.3%) p=0.706) and LMD rate (fSRS:15.3% (95% CI 7.0-31.4%) vs. ioRT: 16.5% (95% CI 7.7-33.4%) p=0.745) showed no significant difference. But Patients treated with ioRT showed significantly lower 1-year rates of RN (ioRT: 3.7% (95% CI 0.5-23.5%) vs. fSRS: 21.8% (95% CI 11.7-39.2%) p=0.0002). This was true for asymptomatic and symptomatic RN (fSRS: 14.7% vs. SRS: 1.8%). CONCLUSION ioRT treatment of the resection cavity shows similar oncological outcome as postoperative fSRS regarding overall survival and local control after resection of BM, with significantly lower rates of RN.