Impact of coronavirus disease 2019 on the number of newly diagnosed cancer patients and examinations and surgeries performed for cancer in Japan: a nationwide study

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has rapidly and dramatically influenced healthcare across Japan. However, the influence of the COVID-19 pandemic on the number of newly diagnosed cancer, surgical treatment, and diagnostic examination for cancer types have not been completely investigated all over Japan. This study aimed to analyze the number of cases before and during the COVID-19 pandemic. METHODS: This retrospective study was a survey that asked to provide the number of cases diagnosed with gastric, colorectal, lung, breast, and cervical cancer between January 2019 and December 2020. The survey was sent to tertiary healthcare hospitals, including national cancer institutions, university hospitals, and general hospitals, all over Japan. Data obtained from 105 of 486 surveyed hospitals were evaluated, and the number of cases in each quarter in 2020 was compared with that in the equivalent quarter in 2019. RESULTS: In the second quarter (Q2), significant reductions were observed in the median number of newly diagnosed cases from 2019 to 2020: gastric cancer, 26.7% (43 vs. 32, p < 0.001); colorectal cancer, 17.9% (52 vs. 40, p < 0.001); lung cancer, 12.3% (53.5 vs. 47, p < 0.001); and breast cancer, 13.1% (43 vs. 35.5, p < 0.001). A significant reduction of 11.4% (9 vs. 8, p = 0.03) was observed in the third quarter (Q3) for cervical cancer. In Q2, the number of cases decreased by 30.9% (25 vs. 15, p < 0.001) for stage I gastric cancer, by 27.3% (12 vs. 9, p < 0.001) for stage I colorectal cancer, and by 17.6% (13 vs. 10, p < 0.001) for stage II breast cancer. The magnitude of reduction was significant for the localized stages of gastric, colorectal, and breast cancer according to diagnostic examinations in Q2 and surgical and endoscopic treatment in Q3 rather than that for lung or cervical cancer. CONCLUSIONS: COVID-19 has prolonged collateral effects on cancer care, including examination, diagnosis, and surgery, with significant effects on gastric cancer, followed by colorectal, lung, breast, and cervical cancer in Japan. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12885-022-10417-6.