Hospital surgical volume and colorectal cancer survival in Norway: A nationwide cohort study.

Background: Studies of hospital surgical volume and colorectal cancer survival are inconclusive. We investigated whether surgical volume was associated with survival of patients operated for colorectal cancer in Norway.

Methods: Using Cancer Registry of Norway data, we compared excess mortality from colorectal cancer by hospital surgical volume among 26,989 colon and 9779 rectal cancer patients diagnosed 2009-2020 and followed-up to 31.12.2021. Hospitals were divided into terciles according to their three-year average annual surgical volume; colon: low (< 22), middle (22-73), high (> 73); rectal: low (< 17), middle (17-38), high (> 38). We estimated excess hazard ratios (EHR) with flexible parametric models adjusted for age, year, stage, surgical urgency and surgery location (within/outside patient's residential health trust).

Results: Low-volume hospitals had the highest proportion of late-stage or acutely operated colon cancer patients. Colon cancer patients operated at low- versus high-volume hospitals had significantly increased crude excess mortality (EHR = 1.30; 95 % CI = 1.14-1.48) but no difference after adjustment for age, year, and stage (EHR = 0.97; 0.85-1.11). High-volume hospitals had the highest proportion of late-stage rectal cancer patients and patients operated outside their residential area. Rectal cancer patients operated at low- versus high-volume hospitals did not have significantly different excess mortality before (EHR = 0.84; 0.64-1.10) or after (EHR = 1.03; 0.79-1.35) adjustment for age, year, stage, surgical urgency and surgery location. After accounting for case-mix, hospital surgical volume was not associated with excess mortality from colon (P = 0.40) or rectal cancer (P = 0.22).

Conclusion: Low hospital surgical volume was not associated with poorer colorectal cancer survival.