Incidence of rare cancers in the city of São Paulo, Brazil

Introduction: Rare cancers are a challenge for clinical practice as well as for epidemiology and public health. Studies on this subject are few and limited to the study of cases with scarce epidemiologic information. This study aimed to evaluate the incidence of rare cancers and to compare the demographic, anatomic, and histologic characteristics of rare and nonrare (common) cancers. Methods: Incidence data were obtained from the Population-based Cancer Registry of São Paulo, Brazil. Rare neoplasms were those defined in the RARECARE list, which takes into account an incidence lower than 6/100,000/year. Results: In São Paulo, 20.4% of tumors had an incidence lower than 6/100,000/year from 1997 to 2012, being therefore considered as rare tumors. We identified 11 entities with an incidence greater than 6/100,000/year (common neoplasms) and 186 entities with an incidence lower than 6/100,000/year (rare neoplasms). The mean annual incidence of all cancers was 365 per 100,000 in São Paulo between 1997 and 2012, and the incidence of all rare tumors was 74.5 per 100,000. Conclusions: This study presents the burden of rare cancers in Brazil. It is expected to be an incentive for further studies of these entities in order to know the epidemiologic profile of rare tumors in Brazil and to provide a more effective diagnostic and therapeutic approach.