The phase III PARCER trial randomized 300 postoperative cervical cancer patients to IG-IMRT versus 3DCRT (50 Gy/25 fx ± weekly cisplatin) to compare late ≥G2 GI toxicity. IG-IMRT significantly reduced late moderate-to-severe GI toxicity, establishing it as the preferred adjuvant technique. Using 283 PARCER patients (median follow-up 43 months), this group developed multivariable NTCP models for acute ≥G2 diarrhea, late ≥G2 diarrhea, late ≥G2 GI toxicity, and late persistent GI toxicity. What bowel dose metrics matter? High-dose bowel volumes, specifically V30 and V40, were the most consistent predictors of acute and late GI toxicity. Mean cohort values for the bowel bag were V30 638 cc and V40 447 cc. While we’d love to see some dose-volume thresholds, the authors emphasize that these don’t fully capture the continuous relationship between dose and risk. Instead they recommend pushing V30 and V40 as low as is feasible through optimization as every decrease in these volumes decreases toxicity risk. | Corbeau, Radiother Oncol 2026
