A Canadian study revealed a large volume of undetected cancer cases related to the COVID-19 pandemic, with some cancer types being more impacted than others, according to researchers.

The largest declines in incidence were seen for cervical, endocrine, and prostate cancers, as well as melanoma. Declines in lung and hepatobiliary cancers were much smaller but persisted throughout the period studied.

Researchers reported these findings in the Journal of the National Comprehensive Cancer Network.

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The researchers looked at individuals diagnosed with cancer from September 2016 to September 2020 in Ontario, Canada, and used segmented negative binomial regression models to examine weekly cancer incidence.

The study included data from 358,487 adults diagnosed with cancer. Of this group, 37,479 were diagnosed during the pandemic, from March 15, 2020, to September 26, 2020.

The researchers’ model showed that, at the start of the pandemic (the week of March 15, 2020), there was an immediate 34.3% reduction in the mean cancer incidence volume, compared with pre-pandemic volumes.

However, the immediate drop was followed by a 1% increase in cancer incidence volume in each subsequent week through September 26, 2020.

The immediate decline in cancer incidence was similar for cancers that had screening programs (35.0%) and cancers that did not (33.7%). Both cancer types saw a slow increase in incidence after the immediate drop.

The greatest declines in incidence were seen for cervical cancer (68.1%), endocrine cancer (63.1%), prostate cancer (54.7%), and melanoma (54.6%).

The smallest declines were in hepatobiliary cancer (4.0%), central nervous system cancer (6.5%), lymphoma (7.9%), and lung cancer (13.5%). For lung and hepatobiliary cancers, there continued to be a weekly decline in incidence throughout the pandemic period studied.

An estimated 12,601 fewer individuals were diagnosed with cancer during the COVID-19 period than expected, the researchers wrote. Sociodemographic and clinical characteristics of people diagnosed before and during the pandemic did not differ, indicating that access to diagnostic care was equitable.

“These potentially missed cancer cases, along with the continued decline in cancer incidence in some cancers, raise grave concerns regarding real-world diagnostic delays,” the researchers wrote. “Providers in the system, especially in primary care, will need to quell patient and caregiver concerns regarding ongoing risk of COVID-19 transmission and to reinforce the value of early detection and treatment of cancers.”

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Eskander A, Li Q, Yu J, et al. Incident cancer detection during the COVID-19 pandemic. J Natl Compr Canc Netw. Published online Feb 1, 2022. doi:10.6004/jnccn.2021.7114.