Concomitant chemoradiotherapy for head and neck squamous cell carcinoma: Real-world treatment delivery, toxicity, and survival in Bosnia and Herzegovina.

Real-world evidence on concomitant chemoradiotherapy (CCRT) for head and neck squamous cell carcinoma (HNSCC) in Bosnia and Herzegovina remains limited. We aimed to characterize treatment delivery, toxicity, and survival and identify modifiable barriers to optimal care. This retrospective single-institution cohort study included 116 consecutive patients with HNSCC receiving curative-intent definitive or adjuvant CCRT at University Hospital Mostar during 2012-2022, with follow-up through May 2025. Overall survival (OS) from diagnosis and event-free survival (EFS) from radiotherapy initiation were evaluated using Kaplan-Meier estimates and univariable Cox regression. Most patients (88.8%) presented with stage IVA-IVB disease. Radiotherapy interruptions of ≥4 days occurred in 50.9%, and 51.7% discontinued concomitant chemotherapy. Among 107 cisplatin-exposed patients, 29.0% received a cumulative dose ≥200 mg/m². Median follow-up was 85 months for OS and 78 months for EFS. Estimated 2- and 5-year OS rates were 50.9% and 32.9%, respectively; corresponding EFS rates were 45.7% and 31.0%. Both outcomes differed across stage groups (p < 0.001 for both), with exploratory univariable analyses indicating poorer outcomes in stage IVB than stage III. Acute grade ≥3 toxicity occurred in 74.1%, including one treatment-related death; late toxicity of any grade was documented in 47.4%. This cohort highlights substantial toxicity and frequent treatment-delivery modifications in routine practice. The findings identify priorities for improving treatment continuity, cisplatin delivery, proactive supportive care, renal monitoring, and multidisciplinary coordination, while survival associations remain exploratory.