ESTRO 2024 - Abstract Book

S1081

Clinical - Gynaecology

ESTRO 2024

constraints should be applied to reduce V 15Gy by another 150cc and possibly aim towards reaching the 25th percentile values (700-800cc) for the entire IG-IMRT cohort (Figure 1). No difference was observed in the median values of V 15Gy , V 30Gy and V 40Gy of those with and without grade≥2 GI toxicity or C-MOSES 0-0.7 and >0.7. On investigating relationship with DVH-AUC, patients with grade≥2 diarrhoea and grade≥2 GI toxicity had higher median AUC cc.Gy values (20667cc.Gy vs. 17639cc.Gy) and (20590cc.Gy vs 17686cc.Gy) respectively. Similar difference in cc.Gy values was also observed in those with persistent vs. non persistent diarrhoea (MOSES>0.2) and persistent and non-persistent GI (C-MOSES>0.7) toxicity (Figure 2).

Conclusion:

Distinct dosimetric differences exist in patients with late grade≥2 diarrhoea or those having persistent diarrhoea or GI symptoms after postoperative IG-IMRT. Based on this comparative analysis, a new planning aim of V 15Gy <750cc-800cc is proposed for bowel bag for postoperative IG-IMRT. Furthermore, limiting DVH-AUC 15-45Gy < 17500cc.Gy could lead to further reduction in late GI toxicity. The feasibility of meeting these planning aims and applying DVH-AUC for routine clinical use needs to be prospectively tested.