Pandemic restrictions corresponded with a significant drop in diagnoses of breast, colorectal and prostate cancers as well as melanoma, according to a new Alberta study published in CMAJ (Canadian Medical Association Journal).

“The sweeping and unprecedented measures enacted at the beginning of the COVID-19 pandemic in Alberta had an inevitable impact on cancer care,” writes Dr. Darren Brenner, an epidemiologist in Calgary, Alberta, and associate professor at the University of Calgary’s Cumming School of Medicine, with co-authors. “Even though treatment and urgent surgeries for cancers were prioritized when other procedures were delayed or canceled, preventive and diagnostic services were greatly reduced.”

The study compared survival rates for three groups of patients diagnosed between January 16, 2018, and March 15, 2019; March 16, 2019, and March 15, 2020; and March 16 and December 15, 2020. The researchers divided the third period into a “state of emergency” (SOE) phase (March 16 to June 15, 2020) and post-SOE phase (June 16 to December 15, 2020).

Researchers saw large reductions in the number of new diagnoses for some cancer types during the SOE period, with a drop of 43% (melanoma), 36% (colorectal and prostate) and 33% (breast). In the post-SOE phase, diagnoses increased 9%, 8% and 10% per month, respectively. Other cancers, such as bladder, kidney, lung and cervical, did not show decreases in diagnoses during that period.

“Our findings that early-stage breast and colorectal cancer had the largest decrease in diagnoses suggest that a reduction in screening services during the first wave of pandemic-related restrictions in Alberta resulted in asymptomatic individuals receiving a diagnosis later than they would have otherwise,” write the authors. “These results highlight the importance of screening services in reducing late-stage cancer diagnoses.”

Patients with colorectal cancer and non-Hodgkin lymphoma diagnosed during the pandemic period in 2020 had poorer one-year survival than those diagnosed in 2018.

By December 2020, the rate of diagnoses had returned to a level more in line with pre-SOE levels.

The findings are consistent with studies from the United Kingdom, United States, the Netherlands, Germany, Japan and other parts of Canada. In Ontario, there was a 34% drop in new cancer diagnoses in April 2020, and Manitoba had a 23% reduction in the same period. An estimated 15% reduction in Quebec occurred in the first year of the pandemic.

Cancer care must become more efficient and increase capacity to reduce long-term effects of the pandemic on cancer outcomes, the authors conclude.