[Influence of the COVID-19 pandemic on cancer incidence in Japan].

Objectives　The first case of the novel coronavirus disease 2019 (COVID-19) was confirmed in China in December 2019, rapidly escalating into a global pandemic. The first case in Japan was detected in January 2020 and a state of emergency was declared in April. Citizens were urged to stay at home, and healthcare facilities limited their services. Patients with cancer were compelled to postpone or alter their medical visits, either voluntarily or at the request of the institutions. This study aimed to evaluate the impact of the COVID-19 pandemic on the incidence of cancer diagnosis in Japan.Methods　A summary of the population-based cancer registry data in Japan from 2016 to 2021 from e-Stat was evaluated. The average annual number of cancer cases diagnosed from 2017 to 2019 was then calculated and analyzed compared to the 2020 and 2021 statistics according to age group, cancer site, method of cancer detection, and stage at diagnosis.Results　Between 2019 and 2020, the number of cases decreased by 67,305. Case counts decreased across nearly all cancer sites, except for pancreatic cancer and malignant lymphoma. The most substantial decrease was observed in patients with stomach cancer. Notably, cancers detected through screenings, health checkups, and comprehensive medical exams showed significant decreases, including a 24.0% decrease (5,806 fewer cases) in cases of stomach cancer diagnosis. Declines were observed in the carcinoma in situ, localized, and lymph node metastasis stages for most cancer types. Specifically, for stomach cancer, the number of localized cases decreased by 15.8% (11,596 cases), whereas the number of cases involving lymph node metastasis decreased by 12.7% (1,570 cases). In contrast, from 2020 to 2021, the number of cancer cases increased by approximately 50,000, with growth observed across most sites. Detection through screening and of all stages of cancer, except for those with unknown status, also increased.Conclusion　The number of cancer diagnoses decreased in 2020, particularly cases of early stage cancers. This finding suggests that restrictions related to the pandemic may have limited access to screening and medical visits. The 2021 rebound may reflect the resumption of routine medical services. These findings underscore the importance of assessing the effect of delayed diagnosis during a pandemic on subsequent cancer progression and outcomes.