About Rare Cancers
Rare cancers are generally classified in the group of rare diseases, which is defined in the European Union as diseases with a prevalence of fewer than 5 cases out of a population of 10,000. A table published by the European Medicines Agency (EMA) with information on relevant sources for prevalence data for orphan conditions can be downloaded from the EMA Website.
Given that prevalence – the number of patients with the same diagnosis at a given time – is affected by mortality, however, it has been proposed by the Surveillance of Rare Cancers in Europe (RARECARE) project to consider a definition of rare cancers based on incidence, meaning the number of newly-diagnosed cases per year.
According to this definition, rare cancers are identified as those with an incidence of less than 6 per 100,000 persons per year. Using this definition would help minimise the risk of mistaking a rare cancer (such as testicular cancer), which is frequently cured and thus has a rather high prevalence, for a common cancer, or a frequent cancer (such as small-cell lung cancer), which has a low life expectancy and thus a low prevalence, for a rare cancer.
A presentation on the epidemiology of rare cancers can be downloaded here.
See also the guidance for deliberations on rare cancer trial closures issued by the the U.S. National Cancer Institute (NCI) Office of Cancer Centres on 22 May 2012.