International journal of cancer 2017 07 31141(10) 1971-1980 doi 10.1002/ijc.30899
Surgery is the mainstay curative treatment in most cancer. We aimed to test the new hypothesis that cancer surgery performed during holiday periods is associated with worse long-term prognosis than for non-holiday periods. This nationwide Swedish population-based cohort study included 228,927 patients during 1997-2014 who underwent elective resectional surgery for a cancer where the annual number of resections was over 100. The 16 eligible cancer sites were grouped into 10 cancer groups. The exposure, holiday periods, was classified as wide (14-weeks) or narrow (7-weeks). Surgery conducted inside versus outside holiday periods was compared regarding overall disease-specific (main outcome) and overall all-cause (secondary outcome) mortality. Cox regression provided hazard ratios (HR) with 95% confidence intervals (CI) adjusted for age, sex, comorbidity, hospital volume, calendar period and tumor stage. Surgery conducted during wide and narrow holiday periods were associated with increased HRs of disease-specific mortality for cancer of the breast (HR 1.08, 95% CI 1.03-1.13 and HR 1.06, 95% CI 1.01-1.12) and possibly of cancer of the liver-pancreas-bile ducts (HR 1.09, 95% CI 0.99-1.20 and HR 1.12, 95% CI 0.99-1.26). Sub-groups with cancer of the colon-rectum, head-and-neck, prostate, kidney-urine bladder and thyroid also experienced statistically significantly worse prognosis following surgery conducted during holiday periods. No influence of surgery during holiday was detected for cancer of the esophagus-stomach, lung or ovary-uterus. All-cause HRs were similar to the disease-specific HRs. The prognosis following cancer surgery might not be fully maintained during holiday periods for all cancer sites.