Clues emerge on how HIV increases lymphoma risk.

T wo recent studies provide new clues to why people infected with human immunodeficiency virus (HIV) are at high risk — sometimes very high risk--for lymphoma. One of the studies adds new data linking macrophages in HIV patients with the development of AIDS-related lymphoma (ARL). The other suggests that AIDS patients who develop lymphoma have higher levels of certain cytokines as early as 2 years before their diagnosis. The fi ndings could lead to new prevention and treatment strategies not only for ARL but also for other types of lymphoma, according to the researchers, who presented their fi ndings in April at the annual meeting of the American Association for Cancer Research (AACR). “Because of the homogeneity of ARL, we can use its pathogenesis as a window into other types of lymphoma, which is a very heterogeneous disease,” said Charles Rabkin, M.D. , senior investigator at the National Cancer Institute and author of the cytokine study. Unlike most other lymphomas, ARL is usually high grade and metastatic at diagnosis; patients commonly die within weeks of diagnosis. It’s a common cancer in AIDS patients but did not become an AIDSdefi ning disease until 1985, which suggested that it develops more slowly than other AIDS-related cancers such as Kaposi sarcoma. The simple explanation for its late appearance is that the more time that passes after HIV infection, the more likely one is to develop lymphoma, said Michael McGrath, M.D., Ph.D., a professor at the University of California, San Francisco, and senior author of the macrophage study. “The more complex explanation may involve the evolution of HIV in macrophages that harbor mutations.”