Australasian ACPGBI Risk Prediction Model for 30-Day Mortality after Colorectal Cancer Surgery

Background: Postoperative mortality after colorectal cancer surgery varies across hospitals and countries. The aim of this study was to test the Association of Coloproctologists of Great Britain and Ireland (ACPGBI) models as predictors of 30-day mortality in an Australian cohort. Methods: Data from patients who underwent surgery in six hospitals between 1996 and 2015 (CRC data set) were reviewed to test ACPGBI models, and patients from 79 hospitals in the Bi-National Colorectal Cancer Audit between 2007 and 2016 (BCCA data set) were analysed to validate model performance. Recalibrated models based on ACPGBI risk models were developed, tested and validated on a data set of Australasian patients. Results: Of 18 752 patients observed during the study, 6727 (CRC data set) and 3814 (BCCA data set) were analysed. The 30-day mortality rate was 1 center dot 1 and 3 center dot 5 per cent in the CRC and BCCA data sets respectively. Both the original and revised ACPGBI models overestimated 30-day mortality for the CRC data set (observed to expected (O/E) ratio 0 center dot 17 and 0 center dot 21 respectively). Their ability to correctly predict mortality risk was poor (P < 0 center dot 001, Hosmer-Lemeshow test); however, the area under the curve for both models was 0 center dot 88 (95 per cent c.i. 0 center dot 85 to 0 center dot 92) showing good discriminatory power to classify 30-day mortality. The recalibrated original model performed well for calibration and discrimination, whereas the recalibrated revised model performed well for discrimination but not for calibration. Risk prediction was good for both recalibrated models. On external validation using the BCCA data set, the recalibrated models underestimated mortality risk (O/E ratio 3 center dot 06 and 2 center dot 98 respectively), whereas both original and revised ACPGBI models overestimated the risk (O/E ratio 0 center dot 48 and 0 center dot 69). All models showed similar good discrimination. Conclusion: The original and revised ACPGBI models overpredicted risk of 30-day mortality. The new Australasian calibrated ACPGBI model needs to be tested further in clinical practice.