Cholangiocarcinoma: descriptive epidemiology and risk factors.

In theory, the term of cholangiocarcinoma is reserved for the tumours originating from the intrahepatic bile ducts. The problems of classification of the most frequent hilar tumours and the absence of histopathological confirmation in a large percentage of cases in cancer registries from many countries show the difficulty of establishing the specific epidemiologic behaviour of intrahepatic cholangiocarcinoma (ICC). There are clearly two types of ICC: the first one is the consequence of the recurrent infection of the biliary ducts by the parasites Opisthorchis viverrini and Clonorchis sinensis, and is only seen in the areas of Southeast Asia where liver flukes are endemic. In these areas, incidence and mortality rates of ICC are extremely high. Both parasites have been classified class I carcinogens by the International Agency for Research on Cancer. The other type of ICC is a cancer much rarer but present in the whole world. Some risk factors have been well-established (chronic inflammation of biliary ducts, hepatitis, thorotrast, etc) but many patients do not have any of these factors. An increase in incidence and mortality of this second type of ICC has been seen in recent years, mostly in developed countries. There is an ongoing discussion in the literature about its authenticity and potential causes.

Helicobacter species in cancers of the gallbladder and extrahepatic biliary tract.

Helicobacter species have been found in human bile and biliary tract (BT) tissue and are suspected to cause BT diseases, including gallbladder and extrahepatic cancers, collectively referred to in this work as BT cancers. We conducted a literature review of the epidemiological evidence linking the presence of Helicobacter species in bile or BT biopsies to BT cancers and benign diseases. Reports showed great variability with respect to study methods. Nine studies of BT cancers were identified, all with 30 or fewer BT cancers; eight included cancer-free control subjects and used polymerase chain reaction (PCR) as a means of Helicobacter species detection. In four of these studies, Helicobacter species were detected in patients with BT cancer significantly more frequently than in controls, at least when controls without BT diseases were used. In two studies, no Helicobacter species were detected in either cases or controls. Helicobacter species were also often detected in benign BT diseases such as gallstone disease or chronic cholecystitis. As our current knowledge relies on a few small studies that showed substantial differences, larger studies and more standardised protocols for detecting DNA and antibodies against Helicobacter species are needed to investigate a potential association with BT cancer.

Estimating disease prevalence using census data.

We describe a method of working on publicly available data to estimate disease prevalence in small geographic areas using Helicobacter pylori as a model infection. Using data from the Third National Health and Nutrition Examination Survey, risk parameters for H. pylori infection were obtained by logistic regression and validated by predicting 737.5 infections in an independent cohort with 736 observed infections. The prevalence of H. pylori infection in the San Francisco Bay Area was estimated with the probabilities obtained from a predictive logistic model, using risk parameters with individual-level 1990 U.S. Census data as input. Predicted H. pylori prevalence was also compared to gastric cancer incidence obtained from the Northern California Cancer Center and showed a positive correlation with gastric cancer incidence (P<0.001, R2=0.87), and no statistically significant association with other malignancies. By exclusively using publicly available data, these methods may be applied to selected conditions with strong demographic predictors.