Trends Of Lip, Oral Cavity And Oropharyngeal Cancers In Australia ...

The numbers of cases of head and neck cancers were obtained for the period 1982 to 2008 from the Australian Institute of Health and Welfare (AIHW). The AIHW compiles the Australian Cancer Database, a collation of all primary malignant neoplasms diagnosed in Australia. This is compiled from data provided by state and territory cancer registries through the Australian Association of Cancer Registries. Population-based cancer registries receive information on cancer diagnoses from a variety of sources: hospitals; pathology laboratories; radiotherapy centres; and registries of births, deaths and marriages.

The data were segregated by sex, age, and anatomical site based on the World Health Organisation International Classification of Diseases for Oncology, 3rd edition (ICD-O-3) ICD-10 codes. Age was grouped into 5-year bands 0–4, 5–9, 10–14, 15–19, 20–24, 25–29, 30–34, 35-39, 40–44, 45–49, 50–54, 55–59, 60–64, 65–69, 70–74, 75–79, 80–84 and 85+. Annual mid-year population estimates for the period by age group and sex were obtained from the Australian Bureau of Statistics [22].

Cancers in the present analysis are: “Lip and Oral cavity”, which includes lip (ICD 10; C00); the Oral Tongue (Anterior two-thirds only; C02); Gum (C03); Floor of mouth (C04); Hard Palate (C05.0) and other unspecified parts of mouth (C06). Cancers of the Base of the tongue (C01), Soft palate (C05.1), Uvula (C05.2), Tonsil (C09), Oropharynx (C10) and other ill defined sites of oral cavity and pharynx (C14) were considered separately as cancers of the “Oropharynx”. Malignant neoplasms of salivary glands (C07, C08) and other pharyngeal sites (Naso- and Hypo-pharynx: C11-13) were excluded.

Raw data were re-analysed to calculate crude, age-specific and age-standardised incidence rates. Segi’s world standard population and the direct method were used to calculate age-standardised incidence rates [23].

Time trends in age-standardised incidence rates were analysed using Joinpoint regression modeling [24]. The Joinpoint programme version 3.5.2 was used [25]. This analysis generates discrete points that separate different line segments on a log scale, to describe the trends over time. The analysis involves 0–4 “Joinpoints” and the Monte Carlo permutation method to test the level of significance of the trends. Annual percentage change (APC) of each segment, and annual average of APC with corresponding 95% confidence intervals, were estimated. APC was tested to determine whether the trends are increasing (positive change) or decreasing (negative change). P values of <0.05 were considered statistically significant.