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Learning from the Melbourne experience: How reliable are cancer registry data for hepatocellular carcinoma?

Hepatocellular carcinoma (HCC) is unique among cancers, in that it is the only solid organ malignancy that can be diagnosed on the basis of radiographical criteria given the proper clinical context. Because every other solid organ malignancy requires tissue confirmation, pathologists and oncologists find this unusual. In their populationbased study, Hong et al. conducted a careful study of the incidence of HCC based on clinical diagnostic criteria and compared this to cancer registry data for the same period and population in Melbourne, Australia. They found a 2-fold higher incidence of HCC than reported by cancer registry data attributable to under-reporting of clinical diagnoses. Many registries continue to rely upon tissue confirmation for HCC classification, lumping those without histology into the category “liver cancer unspecified.” This category encompasses any primary liver cancer (e.g., HCC and intrahepatic cholangiocarcinoma, as well as other rare tumors). However, HCC-specific data are needed to truly understand local and global trends in incidence and inform all aspects of epidemiological research on this deadly disease. In the era of electronic health records, many administrative database studies are reporting disease incidence based on international diagnostic coding systems (e.g., International Classification of Diseases [ICD]-9 and ICD-10). However, cancer registries have a specific and important role. Population-based cancer registries are designed to collect data on all new cases of cancer that occur in a well-defined population. When the incidence and prevalence of cancer in a specific community is well quantified and characterized, priorities may be established and future needs assessed. Identifying risk factors and determining effectiveness of screening initiatives and cancer care are important objectives of a cancer registry. A cancer registry seeks to attain high-quality data with careful monitoring of data completeness and validity. Quality control is an essential part of ensuring valid and complete data. For example, the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute (NCI) collects and publishes cancer incidence and survival data from populationbased cancer registries covering approximately 28% of the population of the United States. SEER has been including clinically diagnosed HCC cases for decades. NCI staff in conjunction with the North American Association of Central Cancer Registries work with state registries to achieve uniform data content. However, as Hong et al. demonstrate in their study, in countries where clinical HCC diagnoses are not captured, the fundamental premise on which the data are collected is flawed, leading to incomplete data and falsely low estimates of the incidence and prevalence of HCC. Abbreviations: HCC, hepatocellular carcinoma; ICD, International Classification of Diseases; NCI, National Cancer Institute; SEER, Surveillance, Epidemiology, and End Results.