Association of Immigration Status and Chinese and South Asian Ethnicity With Incidence of Head and Neck Cancer.

Importance: Head and neck cancer (HNC) incidence varies worldwide, although it remains one of the most common cancers among those of East Asian and South Asian ethnicity. Objective: To determine the association of Chinese and South Asian ethnicity, independent of immigration status, with HNC incidence. Design, Setting, and Participants: This was a retrospective population-based matched cohort study that examined data collected between 1994 and 2017 in Ontario, Canada. Data were analyzed between July 2019 and March 2020. Individuals who immigrated to Canada between 1985 and 2017 were classified as immigrants, whereas Canadian-born individuals and those who immigrated prior to 1985 were classified as long-standing residents. Two separate, matched cohorts were created: an immigration cohort, consisting of immigrants and long-standing residents hard matched on age and sex, and an ethnicity cohort, where participants were further matched on ethnicity (Chinese, South Asian, or non-Chinese/non-South Asian). Exposures: Chinese ethnicity, South Asian ethnicity, and immigration status. Main Outcomes and Measures: Patients newly diagnosed with primary HNC were captured in both the immigration and the ethnicity cohorts. Cause-specific hazard models were used to estimate the association of immigration status and ethnicity with HNC incidence. Results: In the immigration cohort, 3 328 434 matched individuals (mean [SD] age, 36.73 [13.46] years; 52.8% female) were followed, across which 3173 unique HNC diagnoses were made. The hazard ratio (HR) for a new diagnosis of oropharynx cancer was lower in immigrants compared with long-standing residents (HR, 0.26 [95% CI, 0.22-0.31]). In the ethnicity cohort, after adjusting for age, sex, rurality, and deprivation, the rate of HNC diagnosis was higher for Chinese individuals (HR, 1.49 [95% CI, 1.36-1.64]) and South Asian individuals (HR, 1.29 [95% CI, 1.14-1.45]), although it was lower for immigrants (HR, 0.48 [95% CI, 0.44-0.52]) when compared with non-Chinese and non-South Asian individuals. There was no difference in the incidence of nasopharynx cancer when comparing immigrants and long-standing residents of Chinese ethnicity. Conclusions and Relevance: Immigration status appears to offer a protective effect against a diagnosis of HNC. Chinese and South Asian ethnic groups may experience higher HNC incidence when compared with the general Ontario population.