We found a significant decrease in the number of screening cases between May and July in 2021 no matter which year we compared that period to, as there was a rise in COVID-19 confirmed cases and a Level 3 alert was implemented in Taiwan, representing an advance in epidemic prevention measures. No matter how many cases of COVID-19 were confirmed inside a particular area, screening cases dropped significantly in all areas of Taiwan, especially in Taipei where most COVDI-19 cases in Taiwan were being found. A proportional decrease in screening numbers was noticed in all areas.
Unlike other countries, Taiwan had a quick response to COVID-19 and implemented a strong restriction policy in order to fight the epidemic. While sporadic cases were still noticed during 2019–2021, small numbers of outbreaks were still found. A Level III alert was applied in May 2021, so the postponing of unnecessary and non-emergency hospital visits was propagated. However, people still had to wait in long queues for taking of temperatures, while also reporting travel, occupation, contact and cluster history. Therefore, a drop in screening number was expected and subsequently confirmed in our research. Screenings for colon cancer, oral cancer, cervical cancer and breast cancer were evaluated separately, with the largest dropped rate being noticed in oral cancer screening. (2020–2021 colon cancer vs. oral cancer vs. cervical cancer vs. breast cancer: -63%, -79%, -65%, 71%, respectively; 2019–2021 colon cancer vs. oral cancer vs. cervical cancer vs. breast cancer: -65%, -83%, -70%, -76%, respectively). As patients were required to remove masks and open mouths when undergoing an oral examination, this practice may have allowed people to become exposed and be at a greater risk of COVID-19 infection. Previous research has demonstrated the impact of COVID-19 on the screening of other cancers, particularly breast cancer [14, 17–19] and colon cancer [14, 16]. In our research, a great reduction in screening numbers was also noticed for both cervical cancer and oral cancer (2020–2021 cervical cancer and oral cancer: -65% and − 79%; 2019–2021 cervical cancer and oral cancer: -70% and − 83%). This may imply that the impact of COVID-19 has been universal and extensive. This innovative finding is important and will have a far reaching impact on cancer screening policy in the future.
We found there was a great reduction in screening numbers accompanied with a rise of COVID-19 cases in Taiwan. Similar to previous research results, a decline in screening numbers corresponded to different COVID-19 incidence rates across different regions [14]. This may imply that a rise in incidences of COVID-19 had a great impact on cancer screening numbers. However, public health policy should also be considered as a reason also. As mentioned above, there was a strict epidemic prevention policy put in place in Taiwan, which may have reduced the will of its citizens to leave their homes and seek medical resources if they did not have an emergent need. While this may have also reduced the rate of screenings at same time, this effect may have been seen on a national level. As for screenings being performed in clinics and hospitals, there were several community screening activities held regularly prior to the era of the COVID-19 pandemic in Taiwan. These activities were however immediately later shut down due to the COVID-19 pandemic at that time [19]. Thus, a great reduction in screening numbers was recorded everywhere in Taiwan, particularly in Taipei. Relatively, COVID-19 prevention policy in Taiwan has been less strict than in other countries and screening willingness may be affected by only the COVID-19 rates across different regions.
Previous research has demonstrated the effect of COVID-19 on breast cancer screening [20], and significant delays in early breast cancer detection was thus noticed. Screening for early breast cancer, including AJCC stage 0 and stage 1, decreased by approximately 51% and 27%, respectively, when compared with the previous year of 2020 in Taiwan, while its effect on other cancer screenings and regional differences was not well evaluated. Having discovered a large screening gap in 2021 in Taiwan, actions should be taken to call back suitable screening candidates for regular cancer screening. Additionally, the longer lasting effects of COVID-19 on other cancer screening should also be analyzed in the future.
There were some strengths surrounding this study. First, we enrolled data regarding all cancer screening which was promoted by the government in Taiwan. This may have helped us to differentiate whether the effect of COVID-19 on cancer screening was universal or not. Second, we had enrolled cancer screening data not only from 2021 and 2020, but also 2019, so the screening reduction rate was calculated not only between 2021 and 2020, but also 2021 and 2019. Additionally, we also compared different screening conditions between the period of the pandemic and the previous non-pandemic period. This may have strongly validated our research, with the possibility of normal fluctuation being alleviated. Third, subgroup data, including different regions and different types of cancer screening were analyzed, thus allowing for a complete picture of impact regarding COVID-19 on cancer screening to possibly become completely uncovered.
There were still some limitations to this study. First, we only enrolled screening data taken from insured individuals in Taiwan. But since most citizens in Taiwan are covered by National Health Insurance, this may have only had a small effect. Second, this is a retrospective cross-sectional study, so causality should be interpreted carefully. Third, other demographic characteristics were not collected. Finally, a lack of data surrounding cancer survival rates and cancer stage distribution is also one of the limitations, as a complete relation between reduction rates in cancer screening and mortality rates or cancer stages could not be evaluated.