RADT-51. SURGICALLY TARGETED RADIATION THERAPY (START) FOR PREVIOUSLY IRRADIATED RECURRENT BRAIN METASTASES: INITIAL REPORT FROM A MULTI-INSTITUTIONAL PROSPECTIVE STUDY

Abstract BACKGROUND The optimal management of previously irradiated recurrent brain metastases is a challenging clinical scenario and despite several salvage strategies, to date no prospective, multi-institutional outcomes for surgically targeted radiation therapy (STaRT) have been reported. OBJECTIVE We sought to assess the efficacy of STaRT for the management of patients with recurrent brain metastases enrolled onto a prospective, multi-institutional study. METHODS A prospective, multi-institutional observational registry (NCT04427384) was created to capture clinical outcomes following brain tumor resection and STaRT using collagen-tile Cesium-131 brachytherapy (GammaTile®, GT Medical Technologies, Tempe, Arizona, USA). Herein, the first 50 consecutive patients with recurrent, previously irradiated brain metastases were assessed for patient demographics, tumor characteristics, and cumulative incidence rates of local failure. RESULTS: 50 consecutive patients with 56 recurrent brain metastases underwent resection (94.6% gross total resection) and STaRT at 19 separate centers. The median age was 60 (Range [R]: 28-81) years; the Male:Female ratio was 1:1; and 50%, 14%, 18%, and 18% of patients had tumors of lung, breast, melanoma, or other, respectively. Median follow up was 12.7 months, and median maximum tumor diameter was 3.0 cm (R: 0.4-5.7). The median time to recurrence after prior radiotherapy was 11.0 months (R: 2.5-44.9) (n=26), with the median time from last radiotherapy treatment to STaRT being 14.1 months (R: 3.5-56.3). After STaRT, cumulative incidences of local failure per-patient at 6, 12, and 15 months were 11.7%, 18.4%, and 22.5%, respectively. Survival probabilities at 6, 12, and 15 months were 79.0%, 65.4%, and 62.4%, respectively. Median overall survival was 22.0 months. Symptomatic adverse radiation effects (AREs) occurred in 3 patients (6%). CONCLUSION This analysis demonstrates encouraging outcomes with STaRT for salvaging previously irradiated, recurrent brain metastases after prior radiotherapy across 19 different centers with a low cumulative incidence rate of local failure and AREs.