Drugs prescribed to boost red blood cell counts in cancer patients who become anemic may actually be raising patients' risk of death, according to a new study led by researchers at Northwestern University's Feinberg School of Medicine.

Cancer patients taking the drugs, known as erythropoiesis-stimulating agents or ESAs, were found to have a 10% higher chance of dying than patients who didn't take the drugs, the researchers found. In addition, they had a 57% higher risk of developing a potentially life-threatening blood clot. The study also suggests that ESAs may be fueling tumor growth, at least for some types of cancers.

The findings are raising serious concerns about a class of drugs widely used -- and marketed -- to cancer patients.

The study, a large-scale review of 51 recent phase III clinical trials including over 13,000 patients, was led by Charles Bennett, MD, the AC Buehler Professor of Economics and Aging at the Feinberg School and a hematologist and oncologist at Northwestern Memorial Hospital and the Jesse Brown VA Medical Center. It appears in Wednesday's issue of the Journal of the American Medical Association.

This study isn't the first to call attention to the dangers associated with these drugs, known by brand names Procrit, Epogen, and Aranesp. In November 2007, the FDA strengthened warning labels on the drugs because several studies had shown that cancer patients who took ESAs died sooner and/or had more rapid tumor growth than patients not on the drugs.

The agency urged doctors who treat cancer patients to use ESAs only for treating anemia caused by chemotherapy (its only approved use in cancer patients), and not for other cancer-related causes of anemia or to treat symptoms like fatigue.

The FDA's Oncology Drugs Advisory Committee plans to convene in March to discuss the cumulative data, including the results from this study.

In the meantime, patients suffering with chemotherapy-induced anemia should talk to their doctors about how best to manage the symptoms.

"Patients and their doctors need to have a clear understanding of the benefits and risks of using ESAs in cancer treatment. It doesn't mean that these drugs should not be used in anyone, just that we must be more careful and cautious," said Len Lichtenfeld, MD, deputy chief medical officer, American Cancer Society.

"ESAs remain valuable drugs, and probably do have a role in clinical medicine and in the treatment of patients with cancer. Ultimately, it will be up to the FDA to make recommendations on indications for the use of ESAs," Lichtenfeld said.