[Impact of COVID-19 on cancer treatment: Results from 18 hospital-based cancer registries in Tochigi prefecture].

Objectives　To show the impact of COVID-19 on cancer treatment in Tochigi prefecture.Methods　The number of cancer cases registered in Tochigi prefecture before (2019) and after (2020) COVID-19 was compared using cancer registry data from 18 member hospitals of the Tochigi Prefecture Cancer Care Collaboration Council. Data were compared by sex, age, patient's address at the time of diagnosis, month of diagnosis, cancer site, cancer stage, and treatment. Data on screenings for stomach, colorectum, lung, female breast, cervix, and prostate cancers were investigated in detail.Results　The total number of registered cancer cases was 19,748 in 2019 and 18,912 in 2020 (a decrease of 836 cases [-4.2%]). Among the total cases, there were 11,223 and 10,511 males in 2019 and 2020, respectively (a decrease of 712 cases [-6.3%]) and 8,525 and 8,401 females in 2019 and 2020, respectively (a decrease of 124 cases [-1.5%]). The decrease was greater among males than among females. There was no decrease in the number of registered patients aged <40 years between 2019 and 2020. Based on the patients' address at the time of diagnosis, there was no decrease in the number of cases from outside of the Tochigi prefecture. Regarding the month of diagnosis, there was a notable decrease in the number of registered patients in May and August of 2020. Among the decrease of 836 cases detected by screening, 689(82.4%) were cases of stomach, lung, colorectum, female breast, cervix, and prostate cancer. The number of registered cases of malignant lymphoma, leukemia, and cancer of the oral cavity and pharynx, pancreas, bone and soft tissue, corpus uteri, and bladder did not decrease between 2019 and 2020. In terms of stage of cancer, the number of registered cases of carcinoma in situ, localized cancer, and regional lymph node metastases was lower in 2020 than in 2019, but there was no decrease in the number of registered cases of distant metastases or regional extension.Conclusion　The number of cancer cases registered in 2020 was lower than in 2019, and the degree of change varied by age, hospital, site, whether the case was detected by screening, and stage of cancer. In particular, a marked decrease was observed in the number of cases detected by screening. Furthermore, the decrease in the number of cancer cases registered in May and August of 2020 were believed to be due to the peak in the spread of COVID-19 and the associated declaration of a state of emergency.