Estimation of the postoperative fatality window in colorectal cancer surgery

Postoperative death measured 30 days after surgery is a conventional quality metric, whereas intervals up to 90 days are increasingly used, although data-driven time windows have scarcely been investigated.

The Swedish Colorectal Cancer Registry was used to identify all patients subjected resection for colorectal cancer between 2007 and 2020. All patients were followed up until 180 days after surgery. A join-point statistical hazard model was used to model a declining hazard to a transition point, followed by a stable death rate. This method was subsequently applied to describe postoperative deaths for the entire cohort and subgroups according to tumour location (colon and rectum).

Some 56 096 patients electively operated on for colorectal cancer during the study interval were included, with a 30-day and 90-day fatality of 805 (1.43%) and 1458 (2.60%) patients respectively. The derived postoperative fatality window, after which the death rate transitioned to a stable rate, was 23.8 (95% c.i. 21.5 to 28.2) days after surgery. There was no significant difference in the time window between rectal cancer (22.9 days; 95% c.i. 15.1 to 28.4) and colon cancer (27.3 days; 95% c.i. 21.4 to 31.8) patients (P = 0.455). However, postoperative fatality time windows were extended in patients aged at least 80 years and with American Society of Anesthesiologists' grade III or IV.

The traditional postoperative time window of 30 days was confirmed to be an appropriate metric in elective colorectal cancer surgery when evaluated with a hazards-based statistical framework. Importantly, this time window is influenced by older age and advanced co-morbidity, which could prompt increased vigilance for these patient groups.