Risk of additional cancers in untreated and treated hairy cell leukemia patients

Importance of the field. One of the feared events encountered in hairy cell leukemia (HCL) survivors is the subsequent development of a malignant neoplasm. The increased incidence of second cancers in HCL has been documented in large epidemiologic studies conducted in various locations on the globe. Areas covered in this review. The authors explore the current clinico-epidemiologic evidence, as well as the immune alterations, that link HCL and its therapies to the development of second cancers. Most relevant publications have been identified through the PubMed/Medline database search. What the reader will gain: Although HCL patients could develop both HCL and secondary malignancies because of a shared genetic predisposition, a common environmental carcinogen, or not yet identified infectious agents, multiple immune defects documented in HCL might play an important role in second carcinogenesis. Furthermore, the 'gold standards' of HCL therapy - cladribine and pentostatin - are associated with profound and prolonged suppression of the CD4(+) T-lymphocyte counts, often in excess of 2 - 3 years. And while there is no clear-cut evidence that pentostatin or interferon-alpha play an established role in generation of an excess of second cancers in HCL, the safety of cladribine, the preferred agent by a majority of clinicians worldwide, in this regard is a still largely unsettled issue. Take-home message: Therefore, it remains to be seen if the immune deficiencies induced by the HCL therapies and their consequences can be offset by the benefit conferred by controlling the leukemic process.