In a recent article published in JAMA Network Open, researchers evaluated the association between the coronavirus disease 2019 (COVID-19)-triggered pandemic and cancer incidence to inform strategies potentially reducing the public healthcare system's vulnerability to future disruptions.
To this end, they performed a population-based cross-sectional study in Manitoba, Canada, among 48378 individuals diagnosed with cancer between January 1, 2015, and December 31, 2021.
Study: New Cancer Diagnoses Before and During the COVID-19 Pandemic. Image Credit: ORION PRODUCTION / Shutterstock
Background
In Canada, like elsewhere globally, health services had to be reorganized to provide care for COVID-19 patients. Modeling studies estimated that these people experienced more advanced disease due to late/missed diagnosis and poor outcomes, including reduced survival.
Data on the association between the COVID-19 pandemic and cancer care health services could help identify strategies for decreasing the healthcare system's vulnerability to similar future disruptions (as the COVID-19 pandemic).
About the study
In the present study, researchers used a cross-sectional study design to examine the new cancer diagnoses before January 2015 and February 2020 (pre-pandemic) and after the COVID-19 pandemic began in April 2020. Additionally, they evaluated the effects of interventions implemented to mitigate the pandemic impact between April 2020 and December 2021. They used the population-based Manitoba cancer registry data to determine cancer cases.
The primary study outcome was the age-normalized cancer incidence rate per 10,0000 individuals. The secondary study outcome was the aggregate difference in the monthly cumulative counterfactual (diagnoses in the absence of COVID-19) versus fitted count.
They categorized cancers into the following sites for examination of incidence rates: lung, breast, prostate, rectal, colon, hematologic, urinary, brain and central nervous system (CNS), head and neck, breast, gynecologic, other digestive, pancreatic, endocrine, melanoma, and other. They also examined rectal, colon, and breast cancers separately for individuals <50, 50-74, and ≥75 years.
Finally, the team used interrupted time-series analysis with a long preintervention period that accounted for baseline or seasonal trends in cancer diagnoses. They calculated counterfactual and fitted estimate ratios and 95% confidence intervals (CIs) and used a forest plot to plot them.
Results
There were 48378 cancer cases diagnosed in Manitoba during 2015-2021, of which 23972 occurred in females. In April 2020, there was a 23% decrease in cancer incidence; however, by June 2020, the difference between the fitted and counterfactual cancer incidence rates became insignificant.
Longer-term decreases in diagnoses occurred for breast, colon, prostate, lung, urinary, melanoma, and brain and CNS cancers. It holds for cancer incidence and cumulative deficits, especially for breast and colon cancer cases in individuals aged 50-74.
Between April and May 2020, there were reductions in breast and colorectal cancer screening programs and the rate of colonoscopies in the Manitoba province. Accordingly, in April 2020, there was a 46% decline in breast cancer incidence. Breast cancer incidence remained 11% lower than the counterfactual until December 2021.
There was a decrease in breast cancer incidence only among women ≥75 years, likely due to reduced availability of diagnostic mammography or hesitancy in seeking medical care during the pandemic.
Rectal cancer incidence decreased in April 2020 by 47%. By May 2020, rectal cancer incidence increased by 5% to the counterfactual, likely because they initiated triaging of individuals with suspected rectal cancer and performed endoscopies on people on the waitlist. Its incidence rate was insignificantly higher than the counterfactual in all three age groups.
Lung cancer incidence remained stable until December 2020 and gradually decreased by 11%. However, the association was seen only for individuals ≥75 years, in whom lung cancer incidence declined by 46% in April 2020.
During this time, the rate of SARS-CoV-2 infections in Manitoba was at an all-time high, leading to more deaths among vulnerable people undiagnosed but having lung cancer, advanced age, and comorbidities. Perhaps they did not even seek health care services.
The 12% decrease in urinary cancer incidence persisted over time without any observed recovery, likely because of reduced abdominal imaging availability throughout the COVID-19 pandemic. On the contrary, the incidence of head, neck, and melanoma cancers, which plunged at the start of the pandemic, 50% and 65% in April 2020, respectively, returned to pre-pandemic levels quickly.
Incidence rates of brain and CNS and endocrine cancer also showed decreases of 26% between April 2020 and December 2021. Case numbers of these cancers were small; hence, the effect of the COVID-19 pandemic on the incidence of these cancers might merely be a random variation. Furthermore,
The COVID-19 pandemic showed no association with the incidence of gynecologic, prostate, pancreatic, or other cancers.
Conclusions
In the current study, the authors noted a substantial heterogeneity in the relationship between the COVID-19 pandemic and cancer incidence for all cancer sites in Manitoba, Canada.
Breast, colon, and rectal cancer incidence decreased substantially between May and April 2020, while breast and lung cancer incidence showed sustained decreases only among individuals 75 years and older. Likewise, there was a sustained decline in urinary, brain, and CNS cancer(s) incidence rates between April 2020 and December 2021.
The study highlighted the total deficits for specific high-fatality cancers, which need healthcare service providers' attention.
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