Impact of the COVID‐19 pandemic on the mortality among patients with colorectal cancer in Hiroshima, Japan: A large cancer registry study

BACKGROUND: This retrospective cohort study aimed to evaluate the impact of the COVID‐19 pandemic on colorectal cancer care and mortality using a large cancer registry in Hiroshima Prefecture, Japan. The study aimed to estimate the all‐cause mortality rates within 1 year of diagnosis among colorectal cancer patients diagnosed during the pandemic period (2020 and 2021) compared to those diagnosed during the pre‐pandemic period (2018 and 2019). METHODS: The day of diagnosis was set as Day 0 and Cox regression models were utilized to estimate crude hazard ratios (HRs) and adjusted HRs, accounting for age, sex, cancer stage, and treatment status. Two sensitivity analyses of overall survival were performed with different cutoffs of the pre‐pandemic/pandemic periods and year‐to‐year comparisons. Subgroup analyses were performed using likelihood ratio tests. RESULTS: A total of 15,085 colorectal cancer patients were included, with 6499 eligible for follow‐up. A median age of included patients was 72 years old, of which 59% were male. The distribution of cancer stages showed little variation between the pre‐pandemic and pandemic periods. With a median follow‐up of 177 days, the number of events was 316/3111 (173 events per 1000 person‐years [E/1000PY], 95% confidence interval [CI]: 154–192 E/1000PY) in the pre‐pandemic period, and 326/2746 (245 E/1000PY, 95% CI: 220–274 E/1000PY) in the pandemic period (crude HR: 1.42, 95% CI: 1.22–1.66; adjusted HR: 1.25, 95% CI: 1.07–1.46). The two sensitivity analyses and subgroup analyses consistently supported these findings. CONCLUSIONS: The study revealed an increased colorectal cancer mortality during the pandemic period, suggesting a continuous impact of the COVID‐19 pandemic on the known and unknown risk factors for colorectal cancer for several years. Further studies are necessary to mitigate the adverse effects on patient outcomes.