Does time to completion of radiation treatment in locally advanced vulvar cancer impact survival?

Abstract

5593 Background: Although well established in cervical cancer, it is unclear whether time from initiation to completion of radiation therapy for vulvar cancer affects survival outcomes. We seek to assess if completion of radiation, either alone (RT) or as concurrent chemoradiation (CRT), within a planned timeframe in locally advanced squamous cell vulvar cancer impacts overall survival (OS). Methods: Women 18 years or older with FIGO stage II to IVA vulvar cancer who received external beam RT or CRT as part of their initial treatment course were identified from the National Cancer Database from 2004-2017. Patients with non-squamous cell carcinoma histology or who received systemic cytotoxic therapies as primary treatment were excluded. Patients who received less than 20 fractions of radiation were also excluded. Time to radiation completion was the number of days from the initiation to completion of radiation. The delay of radiation completion was calculated as the difference between the actual time to radiation completion and predicted duration of radiation. Types of treatment (RT and CRT) were both stratified into groups based on the delay of radiation completion, less than 7 days or greater than 7 days. Chi-square, Fisher Exact ANOVA and Kruskal-Wallis tests were used for analysis. Kaplan-Meier curves with log-rank tests were fit for univariate time-to-event analysis. Multivariable Cox proportional hazard models were fit to assess effects after controlling for confounding. Results: There were 2378 patients identified for analysis (n = 856 RT and n = 1522 CRT). Median age was 67 (IQR 56-78) and the CRT group was younger (p < 0.0001) than the RT group. The majority were white (88.35%) with advanced FIGO stage III or IVA (72.29 %) disease. Median dose of total radiation was 5720 cGy (IQR 5040-6300) with higher doses observed in the greater than 7 days delay group versus less than 7 days, (p < 0.0001). Median follow up was 27.2 (IQR 11.8-57.9) months. For both cohorts, completion of treatment with delay less than 7 days resulted in significant improvement in median survival when compared to treatment completion delay of more than 7 days: RT (Median OS 34.9 versus 21.6 months, p < 0.01) and CRT (58 versus 41.3 months, p < 0.01). On multivariate subset analysis, both completion of CRT and RT were associated with improved OS when treatment was completed with less than 7 days delay vs greater than 7 days delay, CRT (HR 0.869 [95%CI 0.758-0.997]), RT (HR 0.820 [95%CI 0.698-0.964]). Advanced FIGO stage IVA was associated with the greatest increase in hazard of death, (HR 1.758 [95%CI 1.516-2.039]), compared to FIGO stage II. Conclusions: Completion of radiation with less than 7 days delay is associated with improved overall survival, which is independent of concurrent chemotherapy. These findings suggest that strategies to minimize delays in radiation treatment are crucial in treating locally advanced vulvar cancer.