Real-world recurrence and survival in locoregionally advanced head and neck squamous cell carcinoma (LA HNSCC) treated with surgery and adjuvant radiotherapy with or without systemic therapy: A SEER-Medicare analysis.

546 Background: Surgery followed by adjuvant radiotherapy (RT) ± systemic therapy (ST) is the standard of care (SOC) for patients (pts) with resectable LA HNSCC. While prior studies have reported outcomes in the overall resected LA HNSCC setting, this analysis focuses on pts who received SOC using contemporary real-world data. Methods: Using the linked Surveillance, Epidemiology, and End Results-Medicare data, we identified pts aged ≥66 years old and newly diagnosed with stage III/IVA, LA HNSCC between 2007-2019 who received surgery and adjuvant RT ± ST. Outcomes included real-world event-free survival (rwEFS), overall survival (OS), and recurrence. rwEFS was defined as the time from surgery to recurrence or death, whichever is earlier. OS was defined as the time from surgery to death. Both rwEFS and OS were described using Kaplan-Meier analysis. Cumulative incidence of recurrence was described accounting for the competing risk from death. Analyses were stratified by tumor site and type of adjuvant treatment. Results: A total of 321 pts met the inclusion criteria. The median age at diagnosis was 71.4 years; 56.7% had stage IVA disease. Among all patients, 58.9% received adjuvant RT alone, 13.1% received RT + cetuximab, and 28.0% received RT + platinum (22.1% cisplatin-based; 5.9% carboplatin-based). Median rwEFS and OS were 10.9 months (95% confidence interval: 8.5, 13.9) and 49.4 months (34.5, 72.1), with 5-year rates of 20.2% and 46.7%, respectively. The 5-year cumulative incidence of recurrence was 56.9%, with nearly two-thirds (65.5%) of recurrences occurring within the first year after treatment. Across tumor sites, the 5-year rwEFS rate was the highest in oral cavity cancer, while the 5-year OS rate was the highest in oropharyngeal cancer. Across adjuvant treatment groups, pts who received adjuvant RT had numerically lower 5-year rwEFS and 5-year OS rates than those who received RT+ST (Table). Conclusions: Among elderly pts with resected LA HNSCC, while pts who received adjuvant RT+ST showed better outcomes than those who received adjuvant RT alone, survival outcomes remain suboptimal. These findings highlight unmet needs for new paradigms to improve long-term outcomes in resected LA HNSCC. Outcomes by tumor site and adjuvant treatment group. N (%) Median rwEFS, months (5-year rate) Median OS, months (5-year rate) 5-year cumulative recurrence rate Tumor site Hypopharynx 21 (6.5%) 5.5 (8.3%) 18.4 (15.4%) 52.0% Larynx 130 (40.5%) 13.0 (14.7%) 34.5 (35.8%) 55.5% Oral Cavity 90 (28.0%) 10.3 (30.5%) 65.8 (51.9%) 50.6% Oropharynx 80 (24.9%) 10.5 (22.6%) 83.2 (63.2%) 64.7% Adjuvant treatment group RT 189 (58.9%) 9.3 (18.3%) 40.1 (41.7%) 56.2% RT + Cetuximab 42 (13.1%) 16.4 (24.5%) 66.0 (50.4%) 48.5% RT + Platinum 90 (28.0%) 10.9 (21.7%) 79.5 (55.4%) 62.1%