RADT-16. A RETROSPECTIVE COMPARISON OF OUTCOMES AFTER WHOLE BRAIN RADIOTHERAPY AND RAPID SIMPLE (RAPPLE) TARGETED THERAPY FOR BRAIN METASTASES IN MATCHED COHORTS OF PATIENTS WITH POOR PROGNOSIS

Abstract

Abstract BACKGROUND For patients whose poor prognosis does not warrant stereotactic radiosurgery, we use the RAPPLE radiotherapy technique to treat multiple brain metastases. RAPPLE uses single-isocenter, coplanar volumetric modulated arc therapy and a non-stereotactic head-shell with IntegraBite™. Brain metastasis are contoured in a single gross tumour volume and expanded by 3 mm to create a planning target volume, covered by 95-110% of 20 Gy in 5 fractions. Our study compares clinical outcomes after RAPPLE and whole brain radiotherapy (WBRT). METHODS From January 2017 to December 2021, we identified patients receiving a first course of RAPPLE and matched patients receiving a first course of WBRT. Cox regression was used to analyze overall survival and Fine-Gray analysis was used to analyze intracranial progression. For each cohort, we compared patient-reported fatigue before and 2-6 weeks after radiotherapy. RESULTS Each cohort had 137 patients whose median Karnofsky Performance Score was 70. The diagnoses were lung cancer (72%) and other cancers (28%). The median survival was 4.1 months for RAPPLE and 4.2 months for WBRT (log-rank p = 0.8). On multivariable analysis of survival, the radiotherapy technique was not predictive (HR = 0.96, 95%CI: 0.73-1.25, p = 0.7). On multivariable analysis, intracranial progression was more likely after RAPPLE (HR = 1.6, 95%CI: 1.1 – 2.3, p = 0.02). The 18-month risk of intracranial progression was 0.49 for RAPPLE and 0.37 for WBRT (p = 0.04). After RAPPLE, 17% of patients required more focal RT and 4% required salvage WBRT, while after WBRT, 3% required focal RT and 4% required repeat WBRT. After RAPPLE, mean patient-reported fatigue remained stable from baseline to first follow-up (2.18 vs. 2.27, p = 0.9), but after WBRT it worsened (1.95 vs. 2.63, p = 0.002). CONCLUSIONS Ninety-six percent of patients treated with RAPPLE avoided WBRT. Patients reported worse fatigue after WBRT.