ESTRO 2025 - Abstract Book

S4334

RTT - Treatment planning, OAR and target definitions

ESTRO 2025

Results: Of 104 fractions (fx) adapted using LOP, the pMR plan was selected as the most suitable plan in 13fx . LOP3 and LOP4 were used most frequently for 36fx and 41fx, respectively. For patients 1,3,4 and 5, there was no significant difference in CTV-T-LR and ITV coverage between MR-adapted and LOP (all p > 0.05). Patient 2, CTV-T-LR and ITV coverage were reduced by 1.3% (p = 0.0040) and 3.8% (p = 0.0002), respectively, with LOP. Compared to online adaptation, the bladder LOP dose increased by 5% (198 cGy) in 95/104fx; the rectal LOP dose increased by 4.1% (172 cGy) in 84/104fx; the bowel LOP dose increased by 4.1% (205.7 cGy) in 104/104fx (Figure 2).