Breast-cancer patient Christine Van Deven sits in her backyard with her dog Charlie in London, Ont., on June 9, 2023. Ms. Van Deven wonders what might have happened if her cancer had been caught earlier.Nicole Osborne/The Globe and Mail
Significantly fewer cases of cancer were picked up in Alberta during the first wave of COVID-19 than in the past, according to new research that reinforces other Canadian findings that many patients were denied crucial early diagnoses in the beginning months of the pandemic.
The Canadian Medical Association Journal (CMAJ) study, published Monday, concluded that new diagnoses in Alberta of four types of cancer plunged in the spring of 2020, when much of the health system was shuttered to deal with the new virus.
Diagnoses of melanoma, an aggressive skin cancer, were 43 per cent lower than expected in the province during the first three months of the pandemic. New cases of prostate and colorectal cancer were down by 36 per cent, while breast cancer diagnoses were lower by a third. Some of the biggest drops were in early-stage cancers.
The common factor uniting all four types of cancer is that screening tests such as mammograms, colonoscopies and skin tests can catch them before patients begin feeling seriously ill. Usually, the earlier that cancer is found, the easier it is to treat. But during the first wave of the pandemic, pro-active cancer screening programs were all but shut down across the country.
“This really shows the importance of these cancer screening activities,” said Darren Brenner, a cancer epidemiologist at the University of Calgary and one of the authors of the CMAJ study. “It shows that they are working, because as soon as they go away, even for three months, we see a major drop in early-stage cancer diagnoses.”
The phenomenon of missed or delayed cancer diagnoses during the pandemic has been well-documented in Canada and around the world. Just last month, Statistics Canada reported that cancer incidence was 12.3 per cent lower in 2020 than the average annual rate over the previous five years, after adjustments for the growing and aging population.
New cancer diagnoses down in 2020, StatCan says
The question now is what impact those missed diagnoses will have on cancer survival rates in the future. The new Alberta study found that patients with three types of cancer – colorectal, uterine and non-Hodgkin lymphoma – diagnosed in 2020 had slightly lower one-year survival rates than patients diagnosed with the same diseases in 2018.
However, Dr. Brenner said it was too early to say whether that was a true pandemic effect or a random year-to-year variation. Most other Canadian and international research has found no reduction in short-term cancer survival among those diagnosed in 2020.
In Ontario, researchers at ICES, formerly known as the Institute for Clinical Evaluative Sciences, mined multiple administrative databases to determine that an estimated 16,000 cases of cancer in adults were missed between the start of the pandemic and October, 2021.
But when they compared mortality among patients diagnosed in that period to patients diagnosed in 2018 and 2019, they found no difference in one-year survival rates. When they adjusted for age, sex, prediagnosis health, cancer type and other variables, they discovered that patients diagnosed during the pandemic were slightly more likely to survive, unless they had melanoma.
“This was a surprising result. We’re not seeing a negative pandemic impact,” said Rui Fu, a post-doctoral fellow at the Sunnybrook Research Institute in Toronto. “Just from the statistical analysis … there’s a protective effect of the pandemic on one-year overall survival.”
One possible explanation is that cancer patients who were fortunate enough to be diagnosed during the first 18 months of the pandemic went on to receive treatment and surgery faster because missed diagnoses meant there were fewer oncology patients in the pipeline, according to Dr. Fu.
But she and other cancer trackers agree it will take several more years – at least – to get a clear picture of how the pandemic affected cancer outcomes.
“I would personally expect to see more impact on the survival of the cancer cases that were diagnosed later in 2021 because I think that those are the cancers whose diagnoses were delayed, not the ones diagnosed in 2020,” said Talía Malagón, a cancer epidemiologist at McGill University.
Christine Van Deven, 53, of London, Ont., is one of those cancer patients diagnosed later in the pandemic. She turned 50 – the age at which Ontario recommends all women begin getting regular mammograms – in February, 2020, just as COVID-19 took off.
Ms. Van Deven, a mother of two and the general manager of a retirement home, didn’t get her first mammogram until the summer of 2021, after her doctor found a lump in her right breast. The mammogram found nothing of concern, but Ms. Van Deven’s doctor, still worried about the lump, sent her to a cancer surgeon for a second opinion.
That appointment took place in January, 2022, as the Omicron variant and staff shortages battered the health care system. Delays in MRIs and biopsies added up to Ms. Van Deven not being diagnosed until early May.
By that point, her invasive lobular carcinoma was at Stage 3. She had three tumours in her right breast, one of which was the size of a tennis ball. The cancer had spread to her lymph nodes. She had a double mastectomy, followed by chemotherapy and radiation.
Ms. Van Deven wonders what might have happened if her cancer had been caught earlier.
“I believe it could have been a smaller procedure. I really believe it wouldn’t have gone to my lymph nodes. But I can’t say for sure. I just don’t know,” she said.