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

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. 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. 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