Lewei Zhang

Although smoking prevalence in British Columbia (BC) is decreasing, numbers of oral cancers are increasing. This change may reflect new emerging risk factors, including an increase in human papillomavirus (HPV) infections and greater immigration from high-risk countries. Currently, in BC there is no data on the trends in oral cancer incidence and survival by ethnicity or by etiologically clustered oral cancer subsites (oral cavity cancers, OCC, which are predominantly tobacco related; and oropharyngeal cancers, OPC, which are predominantly HPV-related). Oral cancers were retrieved from BC Cancer Registry (BCCR) from 1980 to 2006 and the following information collected: names, demographic, tumor, treatment and outcome information. When specific information was not complete, chart review was done. South Asian (SA) or Chinese ethnicities were determined by using previously generated ethnic surname list. Age-adjusted incidence rates (AAIR), age-specific incidence rates (ASIR) and 5-year survival rates for these three populations were calculated by sex, grouping the cancers into etiologically clustered subsites. Calculations were done for each year from 1980 to 2006. An ethnographic study was then conducted to describe the patterns of access, use and perceptions of SA men towards chewing tobacco-containing betel quid (BQ). Extensive field work included participant observations and semi-structured interviews. We have for the first time shown that the incidence of HPV-related OPC has surpassed that of tobacco-related OCC in men. For female, the incidence rates of OPC increased and OCC unchanged. AAIR for OCC was highest in SA males and females while rates of OPC were highest in general population males and Chinese males. Survival rates for OCC were unchanged and for OPC improved in males. SA had poorest survival rates for OCC. Ethnographic findings revealed that among SA males chewing tobacco-containing BQ was viewed as a culturally accepted practice. Availability of BQ, perceived benefits of chewing, ability to conceal the habit, and a lack of awareness of health risks also supported chewing practices. These findings provide a strong foundation for continued work in this field aimed at identifying effective prevention and treatment strategies for oral cancer.

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