There was an immediate, 34% drop in cancer diagnosis in Ontario, Canada during the start of the pandemic, which was followed by a slow and incomplete recovery, according to a study based in the province.

Research in the March 2022 issue of JNCCN—Journal of the National Comprehensive Cancer Network examined data from the Ontario Cancer Registry from Sept. 25, 2016 through Sept. 26, 2020, to determine the impact of the COVID-19 pandemic on the number of new cancer cases detected.

Researchers found 358,487 adult patients had a new cancer diagnosed during that time period. The week-to-week rate of diagnosis was steady before the pandemic, but dropped 34.3% in March of 2020. After that, there was a trend of 1% increase in new diagnoses every week for the rest of the study period.

“Our data demonstrates that many cancers have gone undetected due to the disruptions in the healthcare system in response to the COVID-19 pandemic,” says Antoine Eskander, MD, ScM, ICES, Toronto, Ontario. “This is concerning because a delay in diagnosis for cancer is associated with a lower chance of cure. Healthcare providers should encourage patients to catch up on their cancer screening if any have been missed during the pandemic, and should use a low threshold to investigate patients with any unusual symptoms that may be related to an undiagnosed cancer.”

The drop in new diagnoses was found in both screening cancers—those that have formal screening programs such as cervical cancer, breast cancer and colorectal cancer (and sometimes lung cancer)—and non-screening cancers. The researchers estimate approximately 12,600 cancers went undetected between March 15 and Sept. 26, 2020. The largest decreases in diagnoses were found in melanoma, cervical, endocrine, and prostate cancers.

NCCN has also teamed up with cancer groups across the country to share information about the importance and safety of cancer screening. Learn more about how “Cancer Won’t Wait and Neither Should You” at

To read the entire study, visit