Incidence of thyroid cancer in New Caledonia, South Pacific, during 1985-1992

Abstract

This study was designed to estimate the incidence and describe characteristics of thyroid cancer among several ethnic groups in New Caledonia, South Pacific. The authors located all of the new pathology diagnoses of primary thyroid cancer that occurred in the 164,173 inhabitants (1989 census) from January 1985 to December 1992. Subject and disease characteristics were abstracted from medical records, and histology was classified according to the World Health Organization's histologic classification of thyroid cancer. The average annual rate of thyroid cancer was 9.1/100,000 population (119 subjects). The highest rates were observed in the Island of Lifu (31.5/100,000). The incidence was higher in females than in males (age-adjusted rate ratio = 7.83; 95% confidence interval (CI) 4.47-13.58) and in Melanesians than in other ethnic groups, especially in subjects aged 45-54 years (rate ratio = 8.27; 95% CI 3.36-20.35) and 55-64 years (rate ratio = 8.83; 95% CI 3.21-24.32). Most cancers were papillary (82 subjects); for follicular cancers, the increased risk among Melanesians was more marked after 44 years of age. Melanesians were also more likely to have a metastatic tumor than were other ethnic groups (rate ratio = 2.99; 95% CI 1.64-5.45). With the highest incidence rates ever reported, thyroid cancer is a major public health problem for Melanesians of New Caledonia.