ESTRO 2025 - Abstract Book

S4420

Late-breaking abstracts

ESTRO 2025

without increasing exposure to organs-at-risk (OARs) such as bowel and bladder while preserving target volume coverage (Table 1). One-year PIF rate was 27.8% (22/79), with 5 categorized as mild and 17 evident. 34% of all patients reported bone-related symptoms, 17% potentially related to CRT and subsequently 12 of the 22 patients with MRI detected PIF reported bone pain (57.1%), (Table 2).

Conclusion This is the first study to demonstrate that bone-sparing radiotherapy reduced PIF rates compared to historical data without compromising target coverage or increasing OAR toxicity. Further follow-up will assess long-term clinical impact and validate predictive PIF risk factors.

Keywords: Anal cancer, PIF, Bone sparing radiotherapy

References 1. Pelvic insufficiency fractures, dose volume parameters and plan optimization after radiotherapy for rectal cancer. Kronborg CJS et al. Clin Transl Radiat Oncol. 2019 2. Pelvic Insufficiency Fractures and Bone Pain after Radiation Therapy for Anal Cancer: Relation to Pelvic Bone Dose-Volume Parameters, Kronborg C et al. Adv Radiat Oncol. . 2022 3. DACG_Onkologisk-bh-af-lokaliseret-analcancer_v.3.0_AdmGodk310524.pdf