Although our study found that fewer patients were diagnosed with CRC during the COVID-19 pandemic than before the pandemic, their diseases were more advanced and complicated, which consequently increased the number of emergency surgeries, open surgeries, stoma formations, and postoperative complications. Despite the lack of significant differences in the pathologic results, more patients should have received adjuvant chemotherapy following surgery.
The survival rates of CRC in Korea have been reported to be the highest worldwide; the 5-year survival rates are 71.8% for colon cancer and 71.1% for rectal cancer [18]. Although the CONCORD-3 study group did not discuss the reasons in detail, a possible explanation is that the Korean healthcare system, which started its national cancer screening program in 1999 and expanded it to include CRC in 2004, is responsible [19]. Easy access to medical services based on low costs contributes to better survival rates given that Koreans aged ≥50 years can receive fecal occult blood tests at no cost. Moreover, Koreans with positive fecal occult blood test results are recommended to undergo colonoscopy at no cost. The number of doctor consultations per person and average length of hospital stay in Korea have been among the highest in the Organization for Economic Co-operation and Development countries [20]. Individuals who do not meet the CRC screening criteria but wish to undergo colonoscopy can do so for only US$ 80.
Despite the better accessibility and lower prioritization of CRC management than in other countries, fewer patients were diagnosed with CRC during the COVID-19 pandemic in this study. Similar findings have been observed from other countries [15, 21, 22]. Miyo et al. reported reductions in surgeries and colonoscopies of 10.4% and 14%, respectively, in Japan in their retrospective study [23]. Two other single-center studies in Korea showed 5.4% and 24.3% decreases in CRC patients between 2019 and 2021, respectively [24, 25]. The nationwide database showed an increase in CRC patients from 1999 to 2011, followed by a decrease owing to the aforementioned cancer screening program [26]. However, our study found an 18% decrease over the last 2 years, which is much larger than the average decrease between 2015 and 2019 (i.e., 2% per year). This finding indicated a delay in the diagnosis of CRC due to reduced medical screening rather than decreased CRC incidence.
The inevitable delays in the diagnosis of CRC could affect not only a large number of patients but also patients with more advanced and complicated diseases. Although most patient characteristics did not differ in this study, delays in the diagnosis and treatment have resulted in a significant reduction in CRC survival rates from previous studies [27-29]. When potential patients become the “real” patients due to diagnostic delays, the age at diagnosis also increases. Subsequently, other related factors, such as the ASA physical status class, medical and surgical history, and advanced tumor complications, could worsen and easily lead to postoperative morbidity and mortality. In comparison to the prepandemic group, the pandemic group had more preoperative tumor-related problems and postoperative complications within 30 days after surgery. A few reports have shown similar results [15, 22, 30], whereas others have shown no difference in tumor-related complications, including perforation and obstruction, unlike our findings [21, 24, 25, 30]. This difference reflects the limitations of a single-center study, small number of cases, or lack of detailed data. The difference in the rate of emergency surgeries reached a borderline P-value (3.3 vs. 4.6%, P=0.059), despite the fact that the pandemic group had higher rates of complicated symptoms. Contrary to perforation, which nearly always required emergency surgery, patients with obstruction had a variety of alternatives: stent insertion followed by elective surgery or emergency surgery, depending on the severity of their symptoms, preference of surgeons, and available healthcare devices.
The pathologic outcomes did not differ between the prepandemic- and pandemic groups, as indicated in several studies [21, 23]. Adjuvant chemotherapy increased, albeit it is unclear why (drop rate 21.2% vs. 14.1%), not because the stages were advanced but rather because patients with stage 3 cancer were more compliant with chemotherapy. Some studies have revealed advanced pathologic results, including lymphatic invasion, lymphovascular invasion, and lung metastasis, which could have an impact on the prognosis of patients with CRC [24, 25, 30]. However, because these results were analyzed from the early pandemic period database, they potentially could become aggravated within the near future unless the COVID-19 pandemic ends soon. Further assessment for pathologic variables, including tumor diameter, TNM stage, and lymphatic/vascular/perineural invasion is required.
Apart from delays in diagnosis and treatment, screening delays can also affect the prognosis [31]. Despite the gradual increase in CRC screening rates between 2012 and 2019, screening of identified individuals decreased by 6.1% in 2020, the year COVID-19 emerged [32]. Although the rate slightly increased in 2021, it did not return to the levels observed during 2018. This decline should not be ignored because it may lead to lower overall adenoma detection rates as well as the diagnosis of malignancy. Unlike the effects of delayed CRC patient visitation, the effects of omitting screening would not be reflected over a short period considering the progression rates of adenoma to adenocarcinoma. Encouraging people to participate in the national cancer screening program and promptly visit their care provider when suspicious symptoms emerge will reduce future socioeconomic costs.
To the best of our knowledge, this study—which was based on a comprehensive database—is the largest multicenter study to reflect the effects of the COVID-19 pandemic on various aspects of CRC. However, due to the study’s retrospective design, one of the limitations was selection bias. No stratification of the participating institutions, surgeons, surgical techniques, and treatment policies was possible. Even though all the participating institutions were tertiary, large-volume centers in Korea with secured multidisciplinary teams for CRC management, we excluded the clinical stages determined by preoperative imaging studies due to the possibility of inter-observer difference and the discrepancy between the clinical stages and the pathologic ones. Another limitation is the lack of information on the prognosis of participants; however, these data will be examined in a few years through regular surveillance. Lastly, our results cannot be applied to the general population given the differences in healthcare systems and situations among countries.