April 6, 2022 — Research in the March 2022 issue of JNCCN—Journal of the National Comprehensive Cancer Network examined data from the Ontario Cancer Registry from September 25, 2016 through September 26, 2020, to determine the impact of the COVID-19 pandemic on the number of new cancer cases detected. They 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,” explained 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 September 26, 2020. The largest decreases in diagnoses were found in melanoma, cervical, endocrine, and prostate cancers.
“The pandemic has caused dramatic changes in the health care system, including a worrisome decline in cancer screening,” commented Harold Burstein, MD, PhD, Dana-Farber Cancer Institute, who was not involved with this research. “This study is a well done report from Ontario, Canada, where province-wide records are available, and it shows a huge decline in screening for colorectal (colonoscopy), cervical (Pap smear), and breast cancer (mammogram) in the early months of the pandemic. Similar findings have been reported at major health centers across North America, Europe, and other countries with widespread screening programs.”
Dr. Burstein—a member of the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) Panel for Breast Cancer—continued: “Despite the pandemic, it is critical that people continue to get recommended cancer screenings. With the COVID precautions that clinics have put in place, it is very safe for people to see their medical team for routine mammograms, pap smears, and other important testing. Fortunately, here in Boston and many other centers, our numbers of screening mammograms are recovering rapidly after the lull in 2020, and we are doing all we can to remind people of the importance of regular screening.”
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 NCCN.org/resume-screening.
To read the entire study, visit JNCCN.org. Complimentary access to “Incident Cancer Detection During the COVID-19 Pandemic” is available until June 10, 2022.
For more information: www.jnccnorg
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October 21, 2025 
