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≥66years) 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 <8weeks, 3) <1week of intra-treatment break, and 4) treatment interval from surgery to start of RT <8weeks. 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 78years (interquartile range [IQR]=74-83). Median follow-up was 17months (IQR=9-40). Three hundred six patients (69%) received RT. Three delivery metrics were associated with improved outcomes: completion of ≥20 fractions, treatment duration <8weeks, and <1week 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.