The decrease in the incidence of malignant tumors as a consequence of the epidemic of COVID-19
Authors: Stilidi I. S. , Zaridze D. G. , Maksimovich D. M. , Dzitiev D. M. 
Published: June 2022

In 2020 we observed a sudden decline in cancer incidence in Russia in comparison with 2019. The age-standardized rates (ASR) per 100,000 population of cancers that were on increase before 2019 dropped abruptly including cancers of the colorectum, prostate, breast, thyroid, kidney, while for those cancers that steadily decreased including cancers of the lung and stomach, the decrease has speeded up.The difference between predicted and actual number of cases registered in 2020 was 98 142 for all cancers, 24 172 for skin cancer (excluding melanoma), 13202 – for prostate cancer 11 660 – for breast cancer, 9570 – for colorectal cancer, 7235 – for lung cancer, 5450 – for kidney cancer, 3506 for gastric cancer, 2744 for urinary bladder cancer, 2436 – thyroid cancer and 2080 for melanoma.The observed decrease in cancer incidence in 2020 reflects the decrease in the detection rate of cancer. Following arguments might explain this decrease. First the individuals with complains or symptoms who in normal situation would seek medical advice might have barriers for consulting doctor due to isolation and lockdowns. For the same reason the coverage of the population by the check-up programs temporarily decreased including screening for breast, cervix, colorectal and prostate cancer. Regrettably there are no data on the population coverage of these screening programs either before (in 2019) or at the time of COVID epidemic (in 2020).For most of these tumors the effective screening tests are available that if applied correctly with quality control contribute to early diagnosis and consequently to the improvement of survival and decrease in mortality.The decrease in the detection rate of cancer in 2020 and 2021 (still to be seen) will result in the shift of the stage of cancer at diagnosis from early to late stages. The proportion of cancer patients diagnosed at the stages III–IV will increase and will be followed by increase in mortality from cancer.The decrease in cancer detection rate is observed in many counties. The Covid‑19 pandemic affected cancer control in Europe. In one third of the countries in Europe the pressure on the health system created by the Covid –19 pandemic caused interruptions in cancer care.To handle effectively the problem of the underdiagnosis of cancer during the Covid‑19 pandemic we have to address population using all available ways of communication and explain that the decrease in detection rate of cancer will be followed by shifting the stage of detected cancer from early to late stages and this will affect its curability. People should be advised to see doctor immediately for any health problems. To make this advice effective the accessibility of cancer diagnostic and treatment facilities need to return to pre-pandemic level.Screening programs should be restored. However, they need to be adjusted to the WHO guidelines and the existing international experience. WHO guidelines recommend screening for colorectal, breast and cervical cancer. Cervical cancer screening – preferably using HPV testing that is much more sensitive than cytological testing and could be carried out twice in the life at age 35 and 45 years.The evidence-based cancer control program will not only help us to overcome the consequences of the pandemic and returning to the pre-pandemic state but also will promote further decline of cancer mortality.