ESTRO 2025 - Abstract Book

S4113

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2025

The penis was positioned either ventrally (for shorter lengths) or cranially in the midline (for longer lengths). The distance from the caudal side of the cast to the top tattoo was determined each session. Between July 2020 and April 2024 male patients treated for anal cancer at Radiotherapiegroep were included in this pilot. Raystation was used for planning and the mean dose and Dmax to the penis and scrotum were determined. A Mann-Whitney U test was used to compare values. Cast reproducibility was assessed by cone beam CT (CBCT). The scrotum and penis were not allowed to cover the target volumes of the inguinal lymph nodes. When >75% of the number of reported fractions met the definition above, positioning was considered reproducible. Patient records were analyzed retrospectively to determine reported skin toxicity. Results: 26 Men were included, 15 patients with a scrotal cast and 11 without. In 9 out of 15 patients with a cast, both penis and scrotum were positioned in the cast (penis in ventral direction). In 8 of them a CBCT score of >75% was achieved. In one patient this score was not achieved due to abnormal positioning of the penis (to the side). In the remaining 6 patients with cast, the penis was positioned cranially in the midline; 4 of them achieved >75%. Patients with and without cast did not show significant differences in mean dose (Gy) and Dmax (Gy) in scrotum and penis (p>0.05). However, a trend towards a lower Dmax has been observed in patients with a scrotal cast (median 33,1 Gy with cast to 44,7 Gy without). Changes in toxicity due to the cast have not been observed. Conclusion: Our in-house developed cast provides stable positioning of both penis and scrotum, although cranial positioning of the penis potentially reduces stability. The cast may contribute to dose reduction, however, due to the small group size no significant result has been observed. Given its stability in positioning, reproducibility and possible dose reduction, the scrotal cast is considered a valuable addition to the radiotherapy treatment of male anal cancer patients.

Keywords: cast, scrotum, penis