REAL WORLD EVIDENCE FOR ONCOLOGICAL OUTCOMES AFTER RADIOTHERAPY OR SURGERY FOR T1A-T1B GLOTTIC SQUAMOUS CELL CARCINOMA: A POPULATION-BASED COHORT STUDY

Purpose: To compare oncological outcomes after surgery (S) or radiotherapy (RT) for T1a-T1b glottic squamous cell carcinoma (T1GSCC) in a population-based cohort study with a propensity score method (PSM). Methods: Patients diagnosed with T1GSCC from 1999 to 2020 were identified from The Fundação Oncocentro de São Paulo database. Only patients with T1a/bN0M0 treated by RT or S were included. Data on age, gender, tumour stage (T), education level, practice setting, time to S or RT, and local treatment were extracted. Treatment groups were compared with the log-rank test. Subgroups were analysed for overall survival (OS), cancer-specific survival (CSS) and local control (LC) with the Cox proportional test. PSM analysis was used to balance confound factors and compare results of S and RT. Results: Eight hundred eighty-eight patients with T1GSCC treated with S (n=447) or RT (n=441) were included in the study. The median follow-up for the entire cohort was 61 months (S=61 and RT=62). A significant unbalance for T stage, age, and time between the diagnosis and treatment was observed. The 5- and 10-year OS for S versus RT were 76% vs 71% and 60% vs 52% (p=0.02); respectively. The CSS and LC at 5 and 10 years for S and RT were 88% vs. 87% and 82% vs. 84% (p=0.424); and 89% vs. 89% and 73% vs. 72% (p=0.823); subsequently. In the subgroup analysis, S was associated with better OS for T1b (p=0.009), male (p=0.03) and public service patients (p=0.03). For LC and CSS, there were no significant differences in the subgroups. In the PSM cohort of S versus RT with 110 patients each, there was no significant difference in the 5 years OS 72% vs. 74%, 10-year OS 53% vs. 54% (p=0.633); 5-year CSS 80% vs. 83%, 10-year CSS 74% vs. 79% (p=0.596), and LC. Conclusion: T1GSCC has favourable outcomes independently of the treatment method employed. Treatment selection should consider patient/tumour characteristics, local social factors, and patient preference to decide which treatment modality to deliver.