Abstract
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.