Evaluating the impact of COVID‐19 on cancer declarations in Quebec, Canada

BACKGROUND: COVID‐19 affected healthcare worldwide, limited access to healthcare, and delayed cancer screening and diagnosis. In this study, the effect of the first year of COVID‐19 was determined on cancer diagnoses in the province of Quebec, Canada. METHODS: Data were collected from the 13 Quebec Cancer Registry health institutions. Newly diagnosed cancer declarations in the first year of the COVID‐19 (April 2020–March 2021) were compared with the reference periods (averages of 3 previous years). The main focus was on four leading cancers: lung, prostate, colorectal, and breast cancers. Generalized regression models with a poisson approximation and interrupted time series (ITS) analysis were used. Underestimated cases were presented in terms of relative risk (RR) and 95% confidence intervals (CI). The changes in the stage‐specific counts were also assessed in each of the four cancers. Results were illustrated separately for the first 4 months of the pandemic (first wave). FINDINGS: This study estimated an overall under‐reporting of 15.3% (29,019 vs. 24,584) of declarations. This under‐reporting was evident across all age groups above 35 years (p < 0.0001), four primary cancers (p < 0.0001), all stages of cancers (p < 0.0001), and both sexes (p < 0.0001). Based on the relative risks, stage‐specific lung cancer counts were underestimated by 5%–34% in the first wave (0%–11% in the first year), prostate cancer by 16%–46% in the first wave (0%–25% in the first year), colorectal cancer 15%–45% in the first wave (0%–24% in the first year), and breast cancer 3%–45% in the first wave and (0%–28% in the first year). However, no stage‐IV cancers were statically under‐reported compared to the pre‐pandemic era and not even in the first wave. INTERPRETATION: Cancer diagnosis was underestimated due to the COVID‐19 pandemic in the first year; this effect was more evident in the first phase of the pandemic in Quebec. Further research is required to determine the accurate burden of the disease in the long term.