Challenges to delivery and effectiveness of adjuvant radiation therapy in elderly patients with node-positive vulvar cancer

Objective To examine adjuvant radiation therapy (RT) use, patterns of RT delivery, and clinical outcomes in older patients with node-positive vulvar cancer. Methods Using SEER-Medicare linked data, we identified 444 patients (age ≥ 66 years) with node-positive squamous cell vulvar carcinoma, without distant metastases, and treated with primary surgery between 1991 and 2009. We used claims to examine RT use and the following delivery metrics: 1) completion of ≥ 20 fractions, 2) treatment duration < 8 weeks, 3) < 1 week of intra-treatment break, and 4) treatment interval from surgery to start of RT < 8 weeks. We tested associations between RT use and metrics with overall (OS) and cause-specific survival (CSS) using multivariate proportional hazards regression. Results Median age was 78 years (interquartile range [IQR] = 74–83). Median follow-up was 17 months (IQR = 9–40). Three hundred six patients (69%) received RT. Three delivery metrics were associated with improved outcomes: completion of ≥ 20 fractions, treatment duration < 8 weeks, and < 1 week of intra-treatment break. Patients who achieved these 3 metrics demonstrated better disease outcomes compared with surgery alone (OS hazard ratio [HR] for death = 0.62, 95% confidence interval [CI] = 0.46–0.82, P = 0.001; CSS HR = 0.58, 95% CI = 0.40–0.85,P = 0.005). Patients not achieving RT metrics demonstrated marginal improvements in disease outcomes over surgery alone (OS HR = 0.73, 95% CI = 0.55–0.99,P = 0.04; CSS HR = 0.76, 95% CI = 0.52–1.11, P = 0.16). Notably, only 51% of patients who received RT achieved all benchmarks. Conclusions In this cohort of older women with node-positive vulvar cancer, achieving metrics for RT delivery was an important factor for optimizing disease benefits from treatment.