Defining and sparing sexual function-related organs at risk for rectal cancer radiotherapy.

Background and purpose: Sexual dysfunction is a common consequence of pelvic radiotherapy, influenced by psychological, physical, social, and relational factors. Research has focused on vaginal dose and stenosis in females and penile bulb dose and erectile dysfunction in males, with limited attention to domains, such as arousal, desire, and satisfaction. In the Danish Colorectal Cancer Radiotherapy Group, we aimed to: (1) Develop an atlas of sexual function-related organs at risk and (2) Evaluate if these organs at risk could be spared without compromising target coverage in rectal cancer radiotherapy planning. Patient/material and methods: A multidisciplinary approach was adopted, involving oncology, physics, psychology, surgery, and radiology. MRI-based anatomical definitions were established, and an atlas was created for both males and females, including inferior hypogastric plexus, pudendal vessels/Alcock's canal, neurovascular bundle, penile bulb, vagina, paracolpium, and bulboclitoris. For comparative planning standard and sexual function-sparing plans were created for each patient.

Results: A national consensus atlas for sexual function-related organs at risk was developed. Standard plans (n = 15) and sexual function-sparing plans (n = 15) for seven males and eight females were compared. Sparing of pudendal vessels and bulboclitoris was feasible without compromising the standard plan. For sexual function-related organs at risk in or close to the target, D2% could often be improved.

Interpretation: Our consensus-based delineation and planning demonstrate that radiation dose to many sexual function-related organs at risk can be spared or optimized without compromising target coverage or dose to standard organs at risk. Future work includes implementing patient-reported outcomes and integrating these new organs at risk into standard radiotherapy planning.