Sickle Cell Anemia : Life Expectancy, Hydroxyurea Studies

by Food and Drug Administration (FDA)

(Page 2 of 3)

Life Expectancy Improves

Despite the absence of an effective treatment, life expectancy for individuals with sickle cell anemia has improved, said Bonds, as a result of early identification through neonatal screening, early initiation of penicillin therapy, close medical monitoring, and early intervention to relieve the symptoms of a painful episode. A recent study found that half of all patients with sickle cell anemia survive into their 40s.

Rates of early death are highest among those with a severe form of the disease. "Between 10 and 15 percent of patients will have three or more painful crises per year," said Bonds. "The more crises you have per year, the greater your chances of dying prematurely. Your organs become more damaged when they are chronically not receiving enough blood and oxygen."

Some people continue to produce fetal hemoglobin throughout their lives. A study of the life expectancy of people with sickle cell anemia found that adults with high levels of fetal hemoglobin lived longer than those who had low levels.

People with sickle cell anemia who suffer strokes or infections, who are pregnant, or who must undergo surgery may be treated with blood transfusions. Risks of this treatment include the possibility of acquiring a viral illness such as hepatitis and the possibility of organ damage caused by iron overload.

Sickle cell anemia can be cured by a bone marrow transplant, which replaces the defective red blood cells with healthy cells from a donor. But a transplant is not a realistic option for most people with sickle cell anemia, according to Bonds, because of a shortage of compatible donors and because of the risks presented by the drug regimen that is required to prepare a patient for a transplant.

"First you give drugs to kill off the patient's marrow, then you do the transplant to replace the marrow." But the powerful drugs given to kill the patient's bone marrow can be dangerous for someone who has had a stroke or is at risk for stroke, she said.

In January 1995, NHLBI announced the successful conclusion of a five-year, multicenter trial of hydroxyurea in the treatment of sickle cell anemia. The study involved 299 patients ages 18 and older who were recruited at 21 medical centers in the United States.

All patients had experienced at least three painful crises in the year before they entered the trial. Half of the patients received Hydrea and half received a placebo. Neither the patients nor their doctors knew who was taking the drug and who was taking the placebo. Patients who took hydroxyurea had roughly half as many painful crises as those who took the inactive pill.

The trial had been scheduled to conclude in May 1995. However, scientists involved found the results so compelling that they stopped the study early and notified doctors of the results so that all patients who might benefit could be offered the treatment. A report of the trial's findings was published in the May 1995 New England Journal of Medicine.

Hydroxyurea Studies

Hydroxyurea is approved by FDA to treat certain types of leukemia and other cancers. Doctors have been interested in Hydrea for the treatment of sickle cell anemia for about 10 years, since pilot studies in humans showed that the drug could increase the level of fetal hemoglobin in red blood cells.

Because hydroxyurea is already on the market for other uses, it was unnecessary for FDA to issue a Treatment IND (investigational new drug) to make the drug available to patients with sickle cell anemia. A Treatment IND is a mechanism used by FDA to make investigational new drugs available to patients while they are under study.

Bonds, who was the project officer for the multicenter study, cautioned that hydroxyurea treatment is not appropriate for every patient.

"We only recommend it for patients over 18 who have had at least three painful crises in the previous year. The patients have to be monitored very carefully. They must have a blood test every two weeks to ensure that their blood count is not depressed to a level where they might be at risk for infection or bleeding."

Hydroxyurea should not be prescribed for patients who are likely to become pregnant or who are unable to follow instructions regarding treatment.

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