INCIDENCE AND PREDICTORS OF CLINICALLY SIGNIfiCANT ACUTE AND LATE TREATMENT-RELATED TOXICITY AFTER STEREOTACTIC RADIOSURGERY IN 4 OR MORE BRAIN METASTASES

Abstract

Abstract AIMS Selected patients with multiple brain metastases can benefit from stereotactic radiosurgery (SRS). Brain V12 (total brain volume receiving 12Gy including target) can predict for late toxicity in single target benign disease, however their value remains uncertain for multiple brain metastases. We report the incidence and evaluate predictors of toxicity in patients with 4 or more brain metastases treated with single fraction SRS. METHOD 226 patients with 2160 treated metastases from 2014-21 were retrospectively studied. Severe acute toxicity, and symptomatic late toxicity (new/progressive neurological symptoms ≥ 3 months post SRS) with MRI changes suggestive of treatment-effect were analysed. Kaplan-Meier method and cumulative incidence function was used to assess survival and toxicity respectively. RESULTS Median number of metastases per patient was 6 (range 4-41) and median V12 was 11.3cc (range 1.5- 45.2cc). Median overall survival (mos.) was 7.6 months. Absolute incidence of acute grade 3/4 cerebral oedema/haemorrhage was 4.9%. The subgroup developing late SRS-related toxicity (16 patients) had a higher mos. than those without toxicity (25mos vs 5 mos., p <0.002). 9/16 (56%) patients developed Grade 3 or 4 toxicity. 82/226 patients survived >12 months and cumulative incidence function of symptomatic SRS-related late toxicity in this group was 4% at 1 year and 9.5% at 2 years. CONCLUSIONS Within the limits of data available a brain V12 value did not meaningfully predict for late SRS related toxicity in patients with multiple brain metastases. The cumulative incidence of clinically relevant late toxicity remains <10% at 2 years despite accepting a high median V12 to treat these patients.