Postoperative mortality risk assessment in colorectal cancer: development and validation of a clinical prediction model using data from the Dutch ColoRectal Audit

Abstract

Background: As the outcome of modern colorectal cancer (CRC) surgery has significantly improved over the years, however, renewed and adequate risk stratification for mortality is important to identify high-risk patients. This population-based study was conducted to analyse postoperative outcomes in patients with CRC and to create a risk model for 30-day mortality.

Methods: Data from the Dutch Colorectal Audit were used to assess differences in postoperative outcomes (30-day mortality, hospital stay, blood transfusion, postoperative complications) in patients with CRC treated from 2009 to 2017. Time trends were analysed. Clinical variables were retrieved (including stage, age, sex, BMI, ASA grade, tumour location, timing, surgical approach) and a prediction model with multivariable regression was computed for 30-day mortality using data from 2009 to 2014. The predictive performance of the model was tested among a validation cohort of patients treated between 2015 and 2017.

Results: The prediction model was obtained using data from 51 484 patients and the validation cohort consisted of 32 926 patients. Trends of decreased length of postoperative hospital stay and blood transfusions were found over the years. In stage I-III, postoperative complications declined from 34.3 per cent to 29.0 per cent (P < 0.001) over time, whereas in stage IV complications increased from 35.6 per cent to 39.5 per cent (P = 0.010). Mortality decreased in stage I-III from 3.0 per cent to 1.4 per cent (P < 0.001) and in stage IV from 7.6 per cent to 2.9 per cent (P < 0.001). Eight factors, including stage, age, sex, BMI, ASA grade, tumour location, timing, and surgical approach were included in a 30-day mortality prediction model. The results on the validation cohort documented a concordance C statistic of 0.82 (95 per cent c.i. 0.80 to 0.83) for the prediction model, indicating good discriminative ability.

Conclusion: Postoperative outcome improved in all stages of CRC surgery in the Netherlands. The developed model accurately predicts postoperative mortality risk and is clinically valuable for decision-making.

Fig. 1

a Postoperative complications, b postoperative surgical complications, c blood transfusion, d duration of hospital stay, and e postoperative mortality for patients with stage I to III and stage IV colorectal cancer by year. Note that for postoperative surgical complications data registration was required from 2011 onward.

Fig. 2

a Flexible calibration curve of the original model. Calibration plot for predicted 30-day mortality in the development cohort (51 484 patients). The calibration slope depicts the strength of predictors. The calibration intercept reflects the calibration in the large, indicating whether predicted probabilities are systematically under- or overestimated. The flexible calibration curve allows examination of calibration across a range of predicted values. A curve close to the diagonal line (i.e. perfect calibration) indicates that predicted (x-axis) and observed probabilities (y-axis) correspond well. The linear bar chart shows the distribution of patients with (= 1) or without (= 0) an observed outcome. Discrimination between a low and high likelihood of 30-day mortality was good (C statistic 0.83, 95 per cent confidence interval (c.i.) 0.82 to 0.84). b Flexible calibration curve of the validation model. Calibration plot for predicted 30-day mortality in the development cohort (32 926 patients). Discrimination between low and high likelihood of 30-day mortality was good (C statistic 0.82, 95 per cent c.i. 0.80 to 0.84). The flexible calibration curve shows some overestimation of predicted risks across the range of true risks. c Flexible calibration curve of the intercept-adjusted model. Calibration plot for predicted 30-day mortality in the development cohort (32 926 patients). Discrimination between a low and high likelihood of 30-day mortality was good (C statistic 0.82, 95 per cent c.i. 0.80 to 0.84). The flexible calibration curve shows some overestimation of predicted probabilities across the between 5 and 30 per cent range of true risks and some underestimation of predicted probabilities across the range of true risks above 30 per cent. RCS, restricted cubic spline.