Is there an association between the COVID-19 pandemic and cancer incidence?

A recent JAMA Network Open study assessed whether the coronavirus disease 2019 (COVID-19) pandemic, caused by the transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), influenced cancer incidence in Manitoba, Canada.

Study: New Cancer Diagnoses Before and During the COVID-19 Pandemic. Image Credit: Stokkete/Shutterstock.com

Background

The ongoing COVID-19 pandemic has massively impacted the global healthcare system. This pandemic resulted in the reorganization of the healthcare system, which included an increase in the use of virtual consultation, redeployment of cancer care staff, and temporary suspension or reduction in cancer screening. 

COVID-19 has significantly disrupted routine healthcare services, which caused missed or delayed diagnoses of cancer. As a result, these individuals could be diagnosed at advanced stages, compromising their survival.

Therefore, it is essential to evaluate how much the cancer care system was affected due to disruptions caused by COVID-19. This insight will be invaluable in formulating effective strategies to prevent the system's vulnerability during future disruptions.

About the study

The current population-based cross-sectional study assessed the association between the COVID-19 pandemic and cancer incidence. This study was conducted in Manitoba, located in central Canada.

CancerCare Manitoba offers clinical services to all Manitoba residents diagnosed with cancer. Before the onset of the pandemic, around 6,000 individuals were diagnosed with cancer.

Among these, 5,000 cancer patients received regular treatment or follow-up care by CancerCare Manitoba.

By the end of March 2020, the government implemented strict COVID-19 restrictions in Manitoba to prevent the spread of the SARS-CoV-2 virus.

In Manitoba, COVID-19 cases peaked, i.e., the first wave occurred in March 2020, the second wave in November 2020, and the third in May 2021. Around 70% of Manitoba residents received full vaccination by October 1, 2021.

This study assessed changes in the rates of new cancer diagnoses before and after the COVID-19 pandemic.

This study included all cancer diagnoses in Manitoba between 2015 and 2021. All relevant data were obtained from the Manitoba Cancer Registry. 

Study findings

48,378 cancer cases were diagnosed between 2015 and 2021 in Manitoba. The median age of cancer patients was 68 years, and 49.6% were female. Around a 23% decrease in cancer incidence was observed in April 2020, and this rate remained unchanged till June 2020. 

The overall age-standardized cancer diagnosis was reduced at the earlier phase of the pandemic. Particularly, a decrease in the incidence rate of melanoma, breast, colon, prostate, urinary, lung, brain, and central nervous system cancers was recorded.

This reduction in cancer incidence rate could be due to decreased breast and colorectal cancer screening programs in Manitoba between April and May 2020. In addition, a significant reduction in the number of colonoscopies in the region could lead to a decreased diagnosis.

In contrast, the increase in rectal cancer incidence could be associated with a central endoscopy waitlist, as most endoscopies are performed in Winnipeg.

The decrease in breast cancer incidence among older women could be due to a reduction in the availability of diagnostic mammography, reluctance to seek medical care during the pandemic, and an increase in mortality rate in this group of individuals due to their higher susceptibility to SARS-CoV-2 infection.

The incidence of lung cancer dropped during the second COVID-19 wave. However, this decrease was only observed among individuals who were older than 75 years of age.

Melanoma cancer incidence also decreased, which could be due to reduced primary care visits. The rate of melanoma cancer incidence increased rapidly to pre-pandemic levels over time.

A long-term decrease in urinary cancer incidence was observed, with no rate of improvement throughout the pandemic. Brain, central nervous system, and endocrine cancer exhibited reduced incidence rates; however, these numbers must be interpreted cautiously because of the reduced number of cases at baseline and inconsistent data.

No association was found between the COVID-19 pandemic and gynecologic and prostate cancer incidence.

Conclusions

The use of high-quality, population-based data is one of the key strengths of this study. Furthermore, interrupted time-series analysis and the inclusion of seasonality are other strengths of this study.

The current study has limitations, including the lack of adjustments of multiple confounding factors during analysis. It also failed to detect individual cancer incidence rates based on the area of their residence and sex. Since this is a single-center study, the findings lack generalization.

Despite the limitations, this study highlighted that the COVID-19 pandemic caused a significant decrease in cancer incidence in Manitoba.

A substantial decrease in colon, breast, and rectal cancer incidence was observed. In the future, similar observational studies must be performed to investigate how the COVID-19 pandemic affected cancer patients in other regions.

Written by

Dr. Priyom Bose

Priyom holds a Ph.D. in Plant Biology and Biotechnology from the University of Madras, India. She is an active researcher and an experienced science writer. Priyom has also co-authored several original research articles that have been published in reputed peer-reviewed journals. She is also an avid reader and an amateur photographer.