Clinical and Treatment-Related Factors Associated With Recurrence After Definitive Radiotherapy for Early-Stage Glottic Squamous Cell Carcinoma: A Retrospective Cohort Study in Panama

Background: Definitive radiotherapy is a standard larynx-preserving treatment for early-stage glottic squamous cell carcinoma. This study evaluated recurrence patterns and freedom from recurrence after definitive radiotherapy in Panama; explored baseline clinical, pathological, and treatment-related factors associated with recurrence; and analyzed initial post-treatment response as an early marker of subsequent recurrence risk. Methods: We conducted a retrospective cohort study of adults diagnosed between 2013 and 2022 with T1-T2 N0 M0 glottic squamous cell carcinoma and treated with definitive radiotherapy at the National Oncology Institute of Panama. Time to recurrence, event-free survival, overall survival, and laryngeal preservation with oncologic control were evaluated. Freedom from recurrence was estimated using the Kaplan-Meier method, with deaths without prior recurrence censored. Survival outcomes were compared using log-rank tests and Cox proportional hazards models. Results: Ninety-four patients were included: 79.8% had T1a, 13.8% had T1b, and 6.4% had T2 disease; 94.7% received three-dimensional conformal radiotherapy. An initial complete response was achieved in 86/93 patients (92.5%). With a median observed follow-up of 65.9 months (38.6-96.6), 17/94 patients (18.1%) developed recurrence: local recurrence occurred in 13.8% and regional recurrence in 4.3%, with no distant metastases. Freedom from recurrence at two and five years was 87.0% and 80.2%, respectively; five-year event-free survival was 70.4%, and five-year overall survival was 81.7%. Laryngeal preservation with oncologic control was achieved in 77/94 patients (81.9%). Partial response was associated with lower five-year freedom from recurrence compared with complete response (28.6% vs. 84.2%; p < 0.001). Five-year freedom from recurrence was 85.4% with hypofractionation and 78.5% with conventional fractionation (p = 0.483). Conclusion: In this retrospective cohort with a median observed follow-up of 65.9 months, definitive radiotherapy achieved a high initial complete response rate, predominantly local recurrence patterns, and a five-year freedom from recurrence of 80.2%, with deaths without prior recurrence censored. Partial response identified a high-risk subgroup as an early post-treatment response marker. Hypofractionation showed a non-significant numerical trend toward higher five-year freedom from recurrence, but the study did not demonstrate superiority, equivalence, or non-inferiority between fractionation schedules.