A feasibility study of sexual organ‐dose sparing volumetric modulated arc therapy in female low rectal cancer patients treated with three‐dimensional conformal radiation therapy

Abstract Background Sexual dysfunction is a significant toxicity of pelvic radiation therapy (RT) for female rectal cancer patients and may be more common with intensity‐modulated techniques compared to three‐dimensional conformal radiation therapy (3D‐CRT). However, limited research has evaluated dose sparing of female sexual organs at risk (OARs), particularly erectile tissues that are critical for sexual function. Purpose This feasibility study aimed to demonstrate the practicality of contouring and sparing female sexual OARs in rectal cancer RT by generating sexual organ–sparing volumetric modulated arc therapy (SO‐VMAT) plans from a small 3D‐CRT cohort and comparing dose distributions to guide future planning. Methods Nine female patients with low rectal adenocarcinoma treated with concurrent chemoradiation using 3D‐CRT were retrospectively analyzed. Sexual OARs (bulboclitoris, external genitalia, and vagina) were contoured and incorporated into replanned SO‐VMAT plans. Institutional dose–volume constraints were applied for standard OARs and planning target volumes (PTVs). SO‐VMAT and 3D‐CRT plans were normalized to equal PTV coverage, and dose–volume metrics were compared using Wilcoxon signed‐rank tests. Results Contouring and sparing of female sexual OARs was feasible in all cases. Compared to 3D‐CRT, SO‐VMAT reduced radiation doses to sexual OARs. For the bulboclitoris, SO‐VMAT lowered V3000cGy and V4000cGy (both p = 0.02). For the external genitalia, SO‐VMAT reduced maximum and mean dose (both p = 0.02) as well as V1000cGy ( p = 0.004) and V2000cGy ( p = 0.01). Vaginal sparing was observed at V4000cGy ( p = 0.03). SO‐VMAT provided significant bladder sparing, whereas bowel and femoral head doses remained comparable. Target coverage remained equivalent between techniques. Conclusion This study demonstrates that female sexual OARs can be systematically contoured and effectively spared during rectal cancer RT using SO‐VMAT. Compared with 3D‐CRT, SO‐VMAT achieved meaningful dose reductions while maintaining target coverage. These preliminary findings support multi‐institutional studies with patient‐reported outcomes to validate clinical relevance and guide integration of female sexual OARs into treatment planning.