Doctors warn of late diagnoses as cancer screening backlog grows

Patients may need extra encouragement to attend routine cancer screening appointments, say cancer experts across Canada.

Many cancer services paused last year during the first wave of the COVID-19 pandemic. While most resumed over the summer, physicians are concerned that routine cancer screening still hasn't bounced back from the slowdown.

Dr. Jonathan Irish, provincial head of surgical oncology at Cancer Care Ontario and Ontario Health, says health systems may face a "tsunami" of patients whose diagnosis and treatment was delayed by the pandemic presenting later with more advanced disease. "The collateral damage of COVID-19 in many areas is going to be significant."

In Ontario alone, hundreds of thousands of people missed routine cancer screening appointments last year.

According to Irish, during the first months of the pandemic, screening mammograms decreased by 97%, pap tests by 88%, and fecal blood tests for colon cancer screening by 73%.

In the case of screening mammograms, service disruptions contributed to a shortfall of more than 152,000 screens between March 15 and May 31, 2020, compared with the previous year. By December, the backlog had doubled to more than 300,000 missed screening mammograms. That number is likely higher now—provincial officials say screening is still being impacted during the third wave and may be scaled back depending on local resources.

Other provinces have seen declines in new cancer diagnoses since the beginning of the pandemic, suggesting that some cancers may be going undetected.

Earlier this year, Quebec officials estimated that 4,119 people with cancer went undiagnosed during the first wave of COVID-19.

According to Dr. Colin Mar, medical director of BC Cancer Breast Screening, the number of cancers detected clinically through symptoms and examination are "almost back to normal" in British Columbia. But the number of screening-detected cancers is not yet back to pre-pandemic levels because participation in screening remains lower than usual.

"We're trying to encourage people to come back," says Mar. Screening programs have enhanced COVID-19 safety measures, including spacing out appointments. Among patients, "there are still some concerns about safety, but also our lives have been so shaken up… people have had to reprioritize things."

In Ontario, cancer screening capacity and participation have ebbed and flowed with the pandemic, says Dr. Keith Stewart, vice-president of cancer services at University Health Network in Toronto.

"As the pandemic lockdown levels rise, the programs to detect cancer fall off," Stewart says. "With a little bit of a lag time, we notice a decrease in referrals and radiation, particularly for cancers detected by screening—breast cancer, colon cancer, cervical cancer."

While patients are still receiving letters recommending screening, Stewart says the volume of people following up is "not where it should be."

"Presumably, it's people saying, 'I'm in lockdown. I can't go out.' Or maybe it's 'I don't want to be around people,' or 'I don't have a caregiver to come with me,'" Stewart says.

Screening services in Thunder Bay have launched a campaign encouraging people to get screened for breast, cervical and colon cancer, warning that "Cancer doesn't stop for COVID-19."

Catch-up screening may also be necessary to clear the backlog of appointments. According to a study published in The Lancet Gastroenterology & Hepatology, without catch-up efforts, even a three-month disruption in colorectal cancer screening could result in hundreds of additional deaths over the next three decades.

Health services could reduce screening backlogs by temporarily expanding capacity. However, a commentary in The Lancet Public Health noted that key components of screening programs, such as cytology and colposcopy, require a skilled workforce that cannot expand quickly, and pushing people to work overtime isn't realistic given the potential for burnout. As such, targeting catch-up screening to the people at the highest risk of cancer may be "the most effective way for screening services to recover."

As things stand, Stewart predicts it may take a long time for health systems to catch up. "It's going to be multiple years… even if we go back up to 100%."