ESTRO 2024 - Abstract Book

S1464

Clinical - Lower GI

ESTRO 2024

completion of treatment (Figure 2) was found. The D50/γ50 was 72 Gy/1.22 and 66 Gy/1.41 for pCR and cCR respectively. Treatment times varied between 1 and 30 weeks and did not correlate significantly with rates of pCR (coefficient of determination: 0.03) or cCR (coefficient of determination: 0.2). Rates of grade 3+ adverse events varied significantly between treatment modalities with the highest rates of events reported on CRT with adjuvant CT (up to 76%) and CT alone (up to 73%) studies and the lowest rates with CRT alone and CRT (up to 23%) and BT alone (up to 19%) studies.

Figure 1: pCR as a function of EQD2 fitted with bounded logistic regression. Data point size is scaled towards size of patient cohort in study arm. RT-radiotherapy, CT-chemotherapy, CRT-chemoradiotherapy, TNT-total neoadjuvant therapy, BT-brachytherapy.