(P047) Which Patients With Inoperable Vulvar Cancer may Benefit From Brachytherapy in Addition to External Beam Radiation? A Surveillance, Epidemiology, and End Results (SEER) Analysis

Abstract

Currently, it remains unknown whether brachytherapy after external beam radiation (EBRT+BT) results in improved outcomes compared to EBRT alone for patients with inoperable vulvar cancer. The purpose of this study was to compare survival outcomes for patients who received these treatment modalities. Data between 1973 and 2011 from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) database were analyzed. Patients with FIGO stage I-IVA vulvar cancer treated with definitive EBRT+BT or EBRT alone were included. Patients with prior surgical resection were excluded. Disease specific survival (DSS) and overall survival (OS) were compared using the Kaplan-Meier method and Cox proportional hazard models. A total of 649 patients were analyzed, of which 617 received EBRT alone and 32 received EBRT+BT. Median follow-up was 13 months. The use of brachytherapy declined from 16% of cases treated in 1973-1980 to 4% in 2001-2011 (p=0.04). EBRT+BT versus EBRT alone was not significantly associated with improved DSS or OS on univariate or multivariate analyses. On post-hoc subgroup analyses, brachytherapy consolidation was associated with a higher 5-year DSS in patients with node-positive disease (60% for EBRT+BT vs 23% for EBRT, p=0.02). Additionally, there was a trend towards a higher 5-year DSS for EBRT+BT in patients with stage IVA disease (53% vs 23%, p=0.052) or tumor size >4cm (45% vs 27%, p=0.08). Finally, EBRT+BT was associated with higher 5-year DSS in a composite subgroup that included patients with stage IVA disease, tumor >4 cm, or node positive disease (52% vs 27%, p=0.02). Utilization of interstitial brachytherapy after EBRT for vulvar cancer is declining in the United States. EBRT+BT is not associated with improved survival compared to EBRT alone in the entire group of patients with inoperable vulvar cancer. Further investigation is required to determine which subgroup may preferentially benefit from brachytherapy consolidation.