Data on patients with cancer of the gall bladder and cancer of the extra-hepatic bile ducts were obtained from the tumour registry in La Paz, Bolivia. Incidence rates were calculated using the Bolivian census data and compared to US incidence data from the Third National Cancer Survey. The age and population standardized incidence rates for cancer of the gall bladder in Bolivia were 5.3/100 000 males/year and 10.3/100 000 females/year. Comparable US rates were 1.0/100 000 males/year and 2.1/100 000 females/year. The age and population standardized incidence rates for cancer of the extra-hepatic bile ducts in Bolivia were 1.1/100 000 males/year and 4.1/100 000 females/year. Comparable US rates were 1.6/100 000 males/year and 1.0/100 000 females/year respectively. Both diseases occurred at younger ages in Bolivia than in the US and both showed marked racial variation. Differences in disease incidence between Bolivia and the US could not be fully explained by differences in age, sex, or racial distributions. Studies designed to investigate the causes of this remarkable variation in disease incidence could provide important clues to disease aetiology.
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ACKNOWLEDGEMENTS Supported in part by grant AM-16549 and contracts 236-79-G-002151, 263-80-P(65>0160 from the National Institutes of Health, a grant to Dr Rios-Dalenz from the Pan American Health Organization, and grants to the Clinical Epidemiology Unit from The Charles A Dana Foundation, The Rockefeller Foundation, and the Andrew W Mellon Foundation.