Cochlear Radiation Dose and Early Hearing Changes After Chemoradiotherapy for Head and Neck Cancer: A Single-Center Retrospective Cohort Study

Background/Objectives: Hearing impairment is a frequent but under-recognized sequela of (chemo)radiotherapy for head and neck cancer (HNC). We assessed the frequency of early post-treatment hearing changes and their association with cochlear radiation exposure and concurrent platinum-based chemotherapy. Methods: We conducted a single-center retrospective cohort study of 70 consecutive patients with HNC treated with radiotherapy between November 2024 and September 2025. Patients receiving concurrent chemoradiotherapy (CRT, n = 48) were compared with patients receiving radiotherapy alone (RT, n = 22). The primary outcome was clinically documented post-treatment hearing change. Cochlear maximum point doses (Dmax) were extracted from treatment plans. Analyses included Fisher exact and Mann–Whitney U tests, Spearman correlations, Firth penalized logistic regression, a Cochran–Armitage trend test, and restricted cubic splines. Results: Post-treatment hearing changes were documented in 38/70 patients (54.3%): 58.3% after CRT versus 45.5% after RT alone (odds ratio (OR) 1.68, 95% confidence interval (CI) 0.61–4.49, p = 0.439). Mean cochlear Dmax was higher in patients with hearing change (median 5.5 vs. 2.5 Gy, p = 0.045) and correlated with the outcome (ρ = 0.244, p = 0.043), with hearing-change rates of 34.8%, 65.2%, and 65.2% across cochlear-dose tertiles (trend p = 0.038). In Firth regression adjusted for age, pre-treatment hearing loss, and concurrent CRT, the association was attenuated and not statistically significant (adjusted OR 1.31 per 10 Gy, 95% CI 0.82–2.08, p = 0.253), and it was attenuated further after accounting for tumor site (OR 1.09 per 10 Gy, 95% CI 0.66–1.80, p = 0.735), with oropharyngeal primary the strongest correlate of hearing change (OR 4.02, 95% CI 1.28–12.6). Paired audiograms were available in only 10 patients, seven of whom showed audiometric deterioration; a conductive component could not be excluded in 14/38 events. No patient exceeded the QUANTEC mean cochlear-dose constraint of 45 Gy. Conclusions: Early, clinically apparent hearing changes affected more than half of this contemporary cohort. The univariable association with cochlear dose did not persist after adjustment, particularly for tumor site, and the available audiometric data do not allow hearing changes to be attributed specifically to cochlear injury. These findings underscore the need for systematic baseline and follow-up audiometry rather than demonstrating that further cochlear-dose reduction would improve hearing outcomes.