Vaginal Sparing Using A Mold In Anal Cancer Female Patients Treated With Intensity Modulated Radiation Therapy: A Dosimetric Feasibility Study

The use of intensity modulated radiation therapy (IMRT) in the organ conservation treatment approach of anal cancers reduces acute morbidity and may improve tumor control. Nevertheless, late complications and quality of life (QOL) outcomes are still disappointing, and sexual dysfunction rates have certainly been under estimated. Our study aims to identify the dosimetric feasibility of vaginal sparing using a mold in anal cancer female patients treated with IMRT. Five consecutive sexually active female patients diagnosed with a localized anal cancer were included in this study after their consent. A personalized vaginal mold was used to dilate the vagina and displace the anterior vaginal wall and vulva from the primary tumor. Computed tomography (CT) scan of the pelvis was performed before and after inserting the mold. From these two acquisitions, we performed three IMRT planning for each patient: without a mold, with a mold without applying dose constraints on the vagina and with a mold and vaginal dose constraints. The doses received by the vaginal wall, the external genitalias (EG) and the organs at risk (OAR) were compared as well as the planning target volume (PTV) coverage using the Wilcoxon/Kruskal-Wallis test. The mold insertion resulted in a vaginal dose (VD) reduction of 12% with a median VD (MVD) lower by 7 Gy. An additional 7% was seen when applying vaginal dose constraints with a MVD lower by 12 Gy (p = 0.009). This benefit was more prominent in the anterior vaginal wall where the MVD were decreased by 16% and 32%, respectively, before and after optimization, resulting in an absolute MVD decrease of 10 Gy and 19 Gy, respectively (p = 0.003). No significant difference was observed in the doses received by 2% of the vagina (D2%) (p = 0.543). Moreover we observed an average of 4 Gy decrease in the median dose to the EG when the mold was inserted (p = 0.021). The PTV coverage was adequate in the three plans with 95% of the PTV receiving more than 95% of the planned dose. The OARs were significantly affected by neither the mold nor the optimization. The Combination of IMRT with the use of a vaginal mold for sexually active anal cancer female patients allows for a dose reduction to the genitals. This could significantly affect the sexual function and subsequently the QOL of those patients and deserves to be tested in the frame of clinical trials.