CHICAGO (Reuters) - Widely used anemia drugs may increase the risk that people with the rare blood disorder known as myelofibrosis will develop leukemia, U.S. researchers said on Monday.
By Julie Steenhuysen
CHICAGO (Reuters) - Widely used anemia drugs may increase the risk that people with the rare blood disorder known as myelofibrosis will develop leukemia, U.S. researchers said on Monday.
The findings may heighten safety concerns over erythropoiesis-stimulating drugs or ESAs, which include Amgen Inc's Aranesp and an older version, Epogen, and Johnson & Johnson's Procrit.
U.S. regulators last month strengthened safety warnings on the drugs amid concerns that they increase the risk of death, heart attack, stroke and the progression of other cancers.
!ADVERTISEMENT!Researchers at the Mayo Clinic in Rochester, Minnesota, have now found these drugs may be associated with a higher risk of leukemia for people with myelofibrosis.
Myelofibrosis is a bone marrow disorder that interrupts the body's normal production of blood cells, leading to severe anemia and enlargement of the spleen.
On its own, myelofibrosis becomes progressively worse. But it can also progress to acute lymphycytic leukemia or lymphoma.
Mayo Clinic researchers examined the records of 311 patients with primary myelofibrosis from 1976 to 2006 to see what factors led some of them to advance to acute leukemia.
"We found an association with erythropoietin and erythropoietin like-drugs," said Dr. Ayalew Tefferi, who presented the study at American Society of Hematology's annual meeting in Atlanta.
Erythropoiesis-stimulating drugs are genetically engineered forms of the naturally occurring human protein, erythropoietin. Natural erythropoietin is made by the kidney and increases the number of red blood cells.
Tefferi said they also found a higher risk with the drug Danazol, a hormone with properties that treat anemia.
"The patients in the study who took the anemia drugs tended to be sicker. Their leukemia could have been caused by other factors," said Amgen spokeswoman Ashleigh Koss.
"It is important to remember that this is a retrospective study, not a prospective study," Koss said. That means it looked back at the patients after they developed the leukemia, an approach less powerful than the prospective approach, which involves studying patients from the beginning of treatment.
A J&J spokesman was not immediately available.
Tefferi agreed that a prospective study was needed. But until such studies could be performed, he said, patients taking the drugs should be carefully evaluated.
"The safety has to be proven," he said in a telephone interview.
Tefferi also said treatment with the drugs could cause further enlargement of the spleen, a known complication of the disease.
