Survival in relation to time to start of curative treatment of colon cancer: A national register-based observational noninferiority study.

Aim: There are ample discussions regarding the timing of treatment, especially in the era after Covid that caused delay to treatment. The aim of this study was to determine whether a delayed start to curative treatment, within 29-56 days after a diagnosis of colon cancer, was noninferior to starting treatment within 28 days, with regard to all-cause mortality.

Method: This is a national register-based observational noninferiority study, with a noninferiority margin of hazard ratio (HR) 1.1, including all patients treated with curative intent for colon cancer in Sweden between 2008 and 2016. The primary outcome was all-cause mortality. Secondary outcomes were length of hospital stay, readmissions and reoperations within 1 year after surgery. Exclusion criteria were emergency surgery, disseminated disease at diagnosis, missing diagnosis date and treatment for another cancer 5 years before colon cancer diagnosis.

Results: A total of 20 836 individuals were included. A period of 29-56 days from diagnosis to start of curative treatment was noninferior versus starting treatment within 28 days for the primary outcome of all-cause mortality (HR 0.95, 95% CI 0.89-1.00). Starting treatment within 29-56 days was associated with a shorter length of stay (average 9.2 vs. 10 days) but a higher risk of reoperation compared to within 28 days. Post hoc analyses demonstrated that surgical modality was driving survival rather than time to treatment. Overall survival was greater after laparoscopic surgery (HR 0.78, 95% CI 0.69-0.88).

Conclusion: For patients with colon cancer, a period of up to 56 days from diagnosis to the start of curative treatment did not lead to worse overall survival.