Oral cancer incidence in British Columbia, Canada since the start of the COVID-19 pandemic

Objectives: Since the beginning of the COVID-19 pandemic, there have been notable disruptions to cancer services worldwide. With interruptions to the opportunistic screening of oral lesions at routine dental visits, an initial decrease in the diagnosis and thus incidence of concerning oral diseases, including oral cancer, is expected at the pandemic's onset. Following this, an increase in the diagnosis and incidence of oral cancer in the early years after the start of the pandemic is anticipated due to the recovery of diagnostic delays. However, it is possible that changes observed in the incidence are also related to contributing factors. While there is literature on the impacts of the COVID-19 pandemic on head and neck cancer incidence, minimal research considers temporal trends, which if not considered, it can bias results. Currently, there is no research on the pandemic's impact on oral cancer incidence beyond 2021, while taking into account temporal trends. This project will determine if the incidence of oral cancer in British Columbia, Canada has changed after the start of the COVID-19 pandemic when considering trends. Methods: Data on the diagnosis of new oral cancers, from January 2010 to December 2022, in British Columbia, were retrieved from the BC Cancer Registry. Cancers of the lip and oral cavity, excluding skin and bone lesions, were included. Salivary gland and pharyngeal cancers were excluded. An interrupted time series design was used to determine differences in oral cancer incidence post-pandemic (2020 and after) by comparing the post-COVID-19 observed incidence to the expected (counterfactual) post-COVID-19 incidence. The expected post-COVID-19 incidence was based on the pre-COVID-19 trend (2010 to 2019). The pre-COVID-19 trend was calculated as the annual percentage change of age-standardized incidence rates using joinpoint regression. Ratios and 95% confidence intervals of observed versus counterfactual post-pandemic age-standardized incidence rates for 2020, 2021, and 2022 were used to determine differences in pre-and post-pandemic incidence. Results: From 2010 to 2022, there were 3039 new cases of oral cancers in the oral epithelium of the lip and oral cavity diagnosed in British Columbia. There were no significant differences between the expected and observed post-COVID-19 oral cancer incidence overall and by sex-specific analysis. Although not significant, there were much fewer observed compared to expected cases of tongue cancers overall and for females. Age category- and site-specific analysis is to be completed. Conclusion: Preliminary results suggest no differences in oral cancer incidence since the onset of the COVID-19 pandemic. Data beyond 2022 should be assessed to continue to determine for differences in oral cancer incidence post-pandemic.