Oral Cancer Trends in Nova Scotia: 1987 to 2011

Oral Cancer Trends in Nova Scotia: 1987 to 2011

Current knowledge of oral cancer incidence and trends is very important in the development of appropriate research questions, preventive strategies, clinical examination and screening protocols, diagnostic procedures, approaches to treatment, surveillance requirements, educational programs and resource allocation.  The purpose of this study was characterize the burden of oral cancer in the province of Nova Scotia, Canada from 1987 to 2011 and to identify any trends in the incidence rates at specific anatomic locations or within specific age or gender groups over this 25 year period.

This was an observational retrospective analysis conducted using data held by the Nova Scotia Cancer Registry, a registry of all cancers diagnosed in residents of the province, except for non-melanoma skin cancers.  Non-aggregate, non-identifiable person level data was obtained from the registry for oral cancer in Nova Scotia between 1987 and 2011. Data obtained included the primary tumor site, gender, age at the time of diagnosis, and the year of diagnosis.  Cases of cancer of the lip, lymphoma, and leukemia were excluded.  Trends in the incidence rates of oral cancer over this time frame were also assessed. 

SEER*Stat software (http://seer.cancer.gov/seerstat/) was used to generate descriptive statistics related to incidence.  JoinPoint Regression software (http://surveillance.cancer.gov/joinpoint/) was used for the analysis of trends in incidence rates using JoinPoint models.

A total of 2206 cases of oral cancer were registered in Nova Scotia between 1987 and 2011.  The most common site was the tongue (26.3%), followed by gum/other mouth (18.0%), tonsil (15.6%), hypopharynx (9.6%), salivary gland (9.5%), floor of mouth (7.6%), oropharynx (4.9%), nasopharynx (4.3%), and other oral cavity (4.2%).  Statistically significant increases in annual percentage change were found in the base of tongue (3.77), tonsil (3.25), tongue (2.7), oral tongue (1.94), and oropharynx (1.67) over the study period.  The only sites to demonstrate a statistically significant decrease in annual percentage change were the hypopharynx (-3.60), floor of mouth (-2.82), salivary gland (-2.54), and gum and other mouth (-1.77).

The largest increases in annual percentage change were found in the base of tongue and tonsil, whereas decreases in annual percentage change were noted in other oral cavity sites such as the floor of mouth and gum/other mouth.  These findings are consistent with trends reported in the literature of increasing incidence rates for oral squamous cell carcinoma at HPV associated sites in the oropharynx (base of tongue and tonsil) and decreasing rates of squamous cell carcinoma within the oral cavity in other western countries.