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Predicting acute diarrhoea in rectal cancer chemoradiotherapy: Secondary analysis of the phase III ARISTOTLE trial
Ying Zhang1, Douglas Brand2, Zhuoyan Shen1
1Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom.
Background:
Neoadjuvant chemoradiotherapy is a standard treatment for locally advanced rectal cancer, but acute diarrhoea remains a significant side effect, affecting the completion of chemoradiotherapy treatment.
Purpose:
This study aimed to predict acute diarrhoea after neoadjuvant chemoradiotherapy for rectal cancer and further develop a strategic tool to individualise rectal cancer treatment.
Materials And Methods:
The ARISTOTLE trial is a phase III trial comparing capecitabine chemo-radiotherapy (CRT) versus capecitabine-irinotecan CRT as a pre-operative treatment for locally advanced rectal cancer. We included 589 trial patients across 73 institutions. The volume of the AI-segmented small bowel receiving at least 10 Gy (V10Gy) was used alongside the treatment arm, patient age, and performance status in a logistic regression model to predict a more than 2-grade increase in acute diarrhoea toxicity from baseline (ΔG ≥ 2). Finally, based on the prediction, we identified a sub-cohort of patients for whom a viable dose decrease would result in a reduction of toxicity, and conversely, we also identified individuals for whom adding irinotecan may not cause toxicity.
Results:
The average mean receiver operating characteristic curve (AUROC) for predicting ΔG ≥ 2 is 0.71 [95 % CI 0.58-0.82] on the independent test dataset. Based on the prediction, we identified 71 patients (14 %) who could potentially benefit from irinotecan addition without a dose decrease to maintain ΔG < 2, and 77 patients (15 %) who could potentially benefit from irinotecan addition but need a dose decrease to maintain ΔG < 2.
Conclusion:
The multi-institutional cohort of 73 centres strengthens the reliability of these findings, demonstrating the model's potential as a strategic tool to individualise rectal cancer treatment while mitigating severe diarrhoea.
