XRT-01. LONG-TERM HEARING LOSS IN CHILDREN WITH MEDULLOBLASTOMA AFTER PROTON IRRADIATION AND CHEMOTHERAPY

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/m(2). 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.