Xrt-01. long-term hearing loss in children with medulloblastoma after proton irradiation and chemotherapy

Abstract PURPOSE To evaluate the incidence and risk factors for hearing loss (HL) among children with medulloblastoma treated with proton irradiation and cisplatin. METHODS We identified children with medulloblastoma ≥3 years of age treated at Texas Children’s Hospital between 2007-2022. Audiograms were graded using the International Society of Pediatric Oncology-Boston scale (SIOP-Boston). Time to grade ≥3 HL was evaluated using Kaplan-Meier and multivariable Cox models to estimate hazard ratios (HR) and 95% confidence intervals (CI). RESULTS Seventy-eight patients (65.4% male) were treated with craniospinal irradiation (CSI) at a median age of 7.6 years (range: 3-21). The mean cochlear irradiation dose was 31.5±9 Gy, and the cumulative cisplatin dose was 295±50 mg/m2. Fifty-six patients (72%) received amifostine. Patients completed a median of 9 audiograms (range: 4-22) with a median audiogram follow-up of 49 months (range: 3-177). Grade ≥3 HL was documented in 25 patients (32%). In adjusted Cox models, mean cochlear dose (HR=1.12, 95% CI: 1.06-1.18) and the age at CSI (HR=0.81, 95% CI: 0.68-0.98) were associated with grade ≥3 HL. Among children who received irradiation after or at 7 years of age, the estimated probability of grade ≥3 HL at three years post-CSI was 12.6% (95% CI: 4.1-34.6) in children exposed to <36 Gy cochlear irradiation and 35.6% (95% CI: 17.4-63.6) in children exposed to >36 Gy cochlear irradiation. Among children who received irradiation before 7 years of age, the estimated probability of grade ≥3 HL at three years post-CSI was 16.5% (95% CI: 5.6-43) in children exposed to <36 Gy cochlear radiation and 66.7% (95% CI: 35.4-93.7) in children exposed to >36 Gy cochlear irradiation. CONCLUSION Long-term follow-up shows that children who received a cochlear dose ≥36 Gy before 7 years of age are at higher risk for HL, regardless of the amifostine and the cisplatin dose.