Results of stereotactic radiosurgery in the treatment of radioresistant brain metastases

Aims: The incidence of brain metastases in patients with renal cell carcinoma (RCC) and malignant melanoma (MM) with radioresistant histologies is over 50%. Stereotactic radiodiosurgery (SRS) may be beneficial in treating radioresistant histologies. The effectiveness of SRS in terms of local control and survival rates in the treatment of patients with radioresistant brain metastases was the focus of our study. Methods: A retrospective review of RCC and MM brain metastases treated with SRS between 2013 and 2020 was conducted. Local control rates, distant brain metastases free survival, and overall survival (OS) were study endpoints. Results: 55 brain metastases were detected in 29 patients, 14 of whom were MM and 15 were RCC. The median follow-up time was 13 (1-89) months. The 1-y and 3-y actuarial local control rates were 82.4% and 59%, respectively. Increased size and volume of brain metastases were associated with progressive disease (p=0.041, p=0.002). Local control rates were increased in those receiving whole brain radiotherapy (WBRT) prior to SRS (0.008). The 1-y and 3-y distant brain metastases free survival were 87.7% and 60.2%, respectively, and increased in those receiving WBRT before SRS, but not statistically significant (p=0.403). The median OS was 8 months (HR: 1.79, 95% CI: 4.48-11.51). There was no difference in OS according to whether the primary disease diagnosis was RCC or MM (p=0.482). Patients with 1-2 brain metastases had better OS than patients with 3 or more brain metastases (p=0.029). Recursive partitioning analysis (RPA) and graded prognostic assessment (GPA) prognostic risk scores were significantly related to OS (p=0.001, p<0.001). OS worsened in patients who received WBRT before SRS compared to those who did not (0.035). OS increased statistically in patients who received immunotherapy (p=0.033). Conclusion: Improvement in local control was found in patients with small tumor diameter and volume. The addition of WBRT to the SRS increased both local control and distant brain metastasis free survival. Regarding OS, multiple metastases, high RPA score, and low GPA score worsened OS. Another crucial observation is that a positive predictive effect on OS was detected in patients in whom immunotherapy was combined with SRS.