Epidemiology of Hematologic Malignancies

Hematologic malignancies include a diverse group of lymphomas and leukemias that arise in cells of the immune and lymphatic systems. In general, genetic errors of normal processes of lymphocyte maturation and activation are believed to be central to lymphomagenesis, suggesting that factors that influence the host immune milieu in a manner that favors the survival and proliferation of transformed lymphocytes are likely to also contribute to their etiology. The following chapter discusses the epidemiology of three broad categories of hematologic malignancies grouped according to common risk factors and biology: Hodgkin lymphoma, non-Hodgkin lymphoma, and multiple myeloma. Each category includes multiple distinct cancers, and in some instances, also clinically relevant molecular subtypes, for which emerging evidence suggests some commonality but also some heterogeneity of etiology. This complexity makes it difficult to capture the unique epidemiology of each type of tumor comprehensively. In the following chapter, we will focus instead on the most common types of hematologic cancer to provide an overview of the epidemiology of these diseases and report the most consistently reported risk factor associations for each cancer subtype.