International variation in the incidence of oral and pharyngeal cancer.

OBJECTIVE

An accurate epidemiological profile is a crucial component of any cancer strategy. The ongoing development of population-based cancer registries provides an invaluable information resource in this regard. Examination of international incidence levels indicates substantial geographical variation. This study assesses the precise extent of such variation.

BASIC RESEARCH DESIGN

The age-standardised rates (ASRs) for oral and pharyngeal cancer (OPC) were analysed for 183 registries in the IARC/WHO publication CIFC-Volume VII.

RESULTS

The median annual age-standardised incidence rates were mouth (2.3 per 100,000), tongue (2.0), lip (1.2), and salivary gland (0.6); the corresponding female rates were mouth (0.8), tongue (0.7), salivary gland (0.4) and lip (0.2). A substantial level of heterogeneity existed between registries in most instances. In the case of males, the highest ASR and the inter-quartile range of ASRs were as follows--mouth (highest rate of 12.4 per 100,000; IQR 1.4 to 3.6), tongue (max. 8.0; IQR 1.1 to 2.9), lip (max. 13.5; IQR 0.3 to 2.4) and salivary gland (max. 4.2; IQR 0.4 to 0.8). Corresponding statistics for females were also recorded. Comb graphs are used to highlight the significance of specific geographical-based trends and putative aetiological factors explored.

CONCLUSIONS

This study reveals substantial international variation in the incidence rates of OPC, with up to 20-fold variation between countries in annual incidence rates for individual sites. The novel presentational technique makes this information readily accessible to non-specialists and highlights the need for disaggregation in future OPC studies.