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Impact of the COVID-19 Pandemic on Inpatient Colorectal Cancer Treatment in Japan: An Interrupted Time Series Analysis Using a National Administrative Database

Year: 2026

Type: article

Abstract: Background: The COVID-19 pandemic disrupted elective endoscopy and non-urgent procedures, but its impact on inpatient colorectal cancer (CRC) treatment in Japan remains incompletely quantified. Methods: We conducted an interrupted time series analysis using the Diagnosis Procedure Combination (DPC) inpatient database. Eligible admissions were patients hospitalized between April 2018 and December 2021 with colorectal cancer codes from the International Classification of Diseases, 10th Revision (ICD-10; C18, C19, and C20) who underwent endoscopic submucosal dissection (ESD) or colorectal surgery. We excluded planned chemotherapy readmissions, recurrence cases, admissions with multiple non-ESD surgeries, and records with missing tumor-node-metastasis (TNM) information. Three periods were defined: Period 1 (Apr 2018-Apr 2020), Period 2 (May 2020-Apr 2021), and Period 3 (May 2021-Dec 2021). Monthly inpatient case volumes were modeled using segmented regression with Prais-Winsten estimation and seasonal adjustment. Results: Of 276,458 eligible admissions, 260,919 were analyzed. At the start of Period 2, adjusted inpatient cases decreased significantly for ESD (-26%; 887 adjusted vs 1,194 predicted; p<0.001) and colectomy (-6%; 2,746 vs 2,928; p=0.043), whereas rectal resection/abdominoperineal resection showed no significant level change (-5%; p=0.189). In stage-stratified analyses limited to surgical resections, Stage I surgical volume decreased significantly at the start of Period 2 (-13%; p=0.010) with no clear reduction for Stages II-IV. Conclusion: In Japan, the early COVID-19 period was associated with short-term reductions in inpatient ESD and Stage I surgical volume, whereas surgical treatment volumes for more advanced disease showed no clear immediate reduction after the first emergency declaration. Because this was an administrative, inpatient-only analysis, the study does not directly assess diagnostic delays, stage migration, or downstream oncological outcomes.

Source: Journal of the Anus Rectum and Colon

DOI: 10.23922/jarc.2026-010