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CHICAGO (Reuters) - Treating cancer patients with anemia drugs increases their risk of blood clots and death, U.S. researchers said on Tuesday, confirming concerns about these widely used drugs.
Researchers said the drugs, erythropoiesis-stimulating agents or ESAs, raise the risk of death by 10 percent in patients who took them compared to those who did not, a finding that could not be explained by the higher blood clot risk alone.
Anemia is a common complication of cancer treatment.
"The findings of mortality are new and are different from prior reports," said Dr. Charles Bennett of Northwestern University in Chicago, whose study appears in the Journal of the American Medical Association.
He said the drugs also increased the risk of blood clots in the lungs and legs by 57 percent in cancer patients, confirming other findings.
"Our findings, in conjunction with basic science studies, raise the concern that the drug may be stimulating cancer and shortening cancer patients' survival," Bennett said in a statement.
Millions of cancer and kidney disease patients take ESAs, man-made versions of a human hormone called erythropoietin. They work by stimulating production of oxygen carrying red blood cells.
Drugs in the class include Amgen Inc's biggest drug Aranesp, and an older version, Epogen, and Johnson & Johnson's Procrit. The study sent shares of both companies lower in extended-hours trading on Monday.
Amgen spokeswoman Ashleigh Koss said the analysis does not define any new risks associated with ESAs, and the blood clot risk is included in current labeling.
She said doctors and their patients need to weigh the drugs' benefit -- avoiding a blood transfusion -- and the risks and use the drug appropriately.
J&J, in a statement, said the study's conclusions "do not provide an accurate reflection of the safety profile" of ESAs when used to treat chemotherapy-induced anemia.
"When used according to product labeling, ESAs remain safe and effective and are the only proven treatment alternative to blood transfusions for patients with chemotherapy-induced anemia," the company said.
Known as a meta-analysis, the study culled data from 51 clinical trials with 13,611 patients who were treated with ESAs or a placebo. It updates a 2006 report from the Cochrane Collaboration, which studies health-care issues, with additional data on 5,000 patients from 13 clinical trials, many of which addressed the issue of survival. The 2006 report did not show an increased risk of death.
The study is an update of a presentation Bennett made to the American Society of Clinical Oncology in June and includes data through January 17, 2008.
The drugs were first approved by the U.S. Food and Drug Administration in 2003 as a treatment for anemic cancer patients to avoid blood transfusions.
The FDA warned of an increased risk of serious and life-threatening side effects in a public health advisory last March on ESAs.
Dr. Michael Henke of the University of Freiburg in Germany, who worked on the latest analysis, said the study would likely affect treatment guidelines.
He said more basic research needs to be done to understand the effects of these drugs on cancer patients.
"We suspect that ESAs activate survival pathways in cancer cells," Henke said, adding that hypothesis needs to be proven conclusively.
The FDA's Oncologic Drugs Advisory Committee plans to review on March 13 recent study results regarding the use of ESAs, including the JAMA study.
"The current FDA recommendation is these drugs are safe for cancer patients as long their hemoglobin levels aren't raised too high. Our data do not support that," Bennett said.
The drugs generated up to $6 billion in cancer-anemia related sales last year for drug companies and represented Medicare's largest drug expenditure, Bennett said.
J&J's shares fell 1.5 percent to $62.76 in after-hours trading, while shares of Amgen fell 1.9 percent to $46.90.
Editing by Will Dunham, Toni Reinhold, Leslie Gevirtz