Do air gaps with image-guided vaginal cuff brachytherapy impact failure rates in patients with high-intermediate risk FIGO Stage I endometrial cancer?

ABSTRACT

PURPOSE: The aim of this study was to assess the impact of air gaps at the cylinder surface on the rate of vaginal cuff failure (VCF) after image-guided adjuvant vaginal cuff brachytherapy (VCBT) in the treatment of high-intermediate risk (HIR) FIGO (Fédération Internationale de Gynécologie et d'Obstétrique (International Federation of Gynecology and Obstetrics)) Stage I endometrial cancer. METHODS AND MATERIALS A retrospective review of patients treated with image-guided VCBT from 2009 to 2016 for HIR FIGO Stage I endometrial cancer was performed. Air gaps present at the applicator surface on the first postinsertion CT were contoured. Vaginal cuff failure-free survival (VCFFS) was measured from the first fraction of VCBT to VCF. RESULTS: A total of 234 patients were identified. Air gaps were present on the first postinsertion CT scan in 82% of patients. The median number of air gaps was 2 (interquartile range [IQR] 1-3), median depth of the largest air gap was 2.7 mm (IQR 2.1-3.4 mm), and the median cumulative volume of air gaps was less than 0.1 cm3 (range < 0.1-0.7 cm3). At a median followup of 56 months (IQR 41-69), 12 patients (5%) experienced VCF, of which 4 had isolated VCF and 8 had synchronous pelvic or distant failure. Five-year VCFFS and isolated VCFFS were 96% (95% confidence interval 93-98%) and 98% (95% confidence interval 96-100%), respectively. On univariate analysis, no factors, including the presence, number, maximum depth, or cumulative volume of air gaps, were predictive for VCFFS. CONCLUSIONS: In this population, VCFFS remained high despite most patients having air gaps present on postinsertion CT scan.