23 Vulvar cancer: Comparative study of novel 3D radiation therapy technique “ Advanced conformal technique ” and AP-PA irradiation techniques

Abstract

Introduction The commonly used technique of vulvar cancer radiation therapy consists of antero-posterior “AP” and postero-anterior “PA” fields. This is the first study that reports dosimetric comparison between the AP-PA techniques and the new 3D radiation therapy technique “advanced conformal technique ACT” based on the multiplicity of treatment fields in patients with squamous cell cancer of the vulva in post-operative setting. Methods This is a comparative planning study of fifteen patients with vulvar carcinoma treated with adjuvant radiation therapy at the National Institute of Oncology in Rabat. Three treatment plans were performed, corresponding to three techniques; photons with source skin distance inguinal supplement, modified segmental boost technique, advanced conformal technique. For each plan, the dose-volume histogram was used to generate target volumes (total and inguinal PTV) and organs at risk OAR (bladder, rectum, bowel and femoral heads) parameters. Results The isodose 95% volume was significantly reduced with the advanced conformal technique (p 0.0001) without compromising the total PTV coverage (p: 0.94). This technique resulted in the best conformity and homogeneity index. The ACT decreased significantly the PTVs Dmax and Dmean (p 0.0001), and offered better homogeneity for inguinal PTV 1.07 ± 0.01 respectively (p 0.0001). The ACT decreased the rectum absorbed dose; V40, V45 and Dmax with 50.21 ± 27.21 22.81 ± 10.22 and 46.56 ± 1.11 respectively. Concerning femoral heads, the ACT decreased the Dmax and V45 in comparison to the both other techniques. Conclusions The ACT seems to be an alternative to the AP-PA irradiation techniques in post-operative setting when IMRT is not available.