Radt-54. Impt-Based Curative-Intent Salvage Re-Rt in Recurrent/Progressive CNS Tumors: First Experience From a Public Hospital in the Lmic Setting

PURPOSE To report preliminary experience of intensity modulated proton therapy (IMPT)-based curative-intent salvage re-irradiation (Re-RT) in a cohort of recurrent/progressive brain tumors treated at the largest tertiary-care cancer centre in India – a low-middle income country (LMIC). METHODS Patients with recurrent/progressive brain tumors treated with salvage IMPT following discussion in a multi-disciplinary neuro-oncology tumor board were identified retrospectively from a prospectively maintained database. Acute toxicity was assessed weekly during Re-RT using CTCAE criteria. Response assessment imaging was scheduled at 4-6 weeks after IMPT-based re-irradiation with periodic clinico-radiological surveillance on follow-up. RESULTS Electronic search of the neuro-oncology database identified 22 consecutive patients treated with curative-intent salvage Re-RT using IMPT. Median age of the study cohort at Re-RT was 37 years (range 6-72 years) with male predilection (59.1%). Histological distribution of recurrent tumors included ependymoma, oligodendroglioma, meningioma, diffuse astrocytoma, craniopharyngioma, pituitary adenoma, mesenchymal sarcoma, and glioblastoma. Median dose at first course of radiotherapy (RT1) was 59.4Gy (range 25-60Gy). Median interval between RT1 and IMPT-based Re-RT was 83 months (range 13-213 months) with 3 patients undergoing repeat Re-RT (third course). Salvage IMPT-based Re-RT was delivered using conventional fractionation to a median dose of 50.4 CGE (range 40-60 CGE) over 5-6 weeks. All patients completed the planned course of IMPT-based Re-RT without interruptions and with minimal acute toxicity. The worst acute toxicity was grade 2 dermatitis seen in nearly 25% of patients. Acute grade 2 CNS toxicity in the form of neurological worsening was seen in 14% of patients who required short course of low-dose steroids during Re-RT for treatment-induced edema. One patient developed post-re-treatment necrosis at 3-months necessitating high-dose steroids for symptom control. CONCLUSION Our preliminary experience of IMPT-based Re-RT for recurrent/progressive brain tumors at a public hospital in LMIC setting is encouraging with excellent tolerance to re-treatment and manageable acute toxicity. Further follow-up and comparative analysis with photon-based Re-RT is required to assess its long-term efficacy, safety, and cost-effectiveness.