Critics say the risk associated with Hopkins' procedure is too high, even for a small trial. They say most sickle cell patients aren't likely to die immediately without a bone marrow transplant.
"I don't think the time is right yet to go ahead with such transplants at full tilt," said Dr. Rainer Storb, an oncologist at the Fred Hutchinson Cancer Research Center in Seattle, which cured several children with sickle cell using bone marrow transplants during the 1990s.
Bone marrow transplants have been used to treat sickle cell disease for 20 years - but almost all of the 200 cured have been children. The treatments - high doses of chemicals that knock out the patient's own marrow before the transplant - are so toxic that adults with sickle cell-induced organ damage would be unlikely to survive them.
Brodsky said his team's procedure, developed by Dr. Ephraim Fuchs and Dr. Leo Luznik, is less toxic. They say they no longer believe they have to destroy as much of the patient's marrow as they once did - so they administer just enough chemotherapy to suppress the immune system. That dose keeps patients from rejecting the new marrow without harming their organs.
This change allows transplants for adults, as well as children. Because the procedure occurs later in life, it relieves parents of the burden of making the decision for their youngsters (even in children, the sickle-cell transplant mortality rate is 5 percent to 10 percent). Instead, it allows the adult patient to see how severe the disease is before deciding whether to have a transplant.
Another transplant obstacle has been finding a perfect bone marrow match - a full sibling's marrow provides the best chance. But there's only a 25 percent chance that even a full sibling will be a match. And since sickle cell is inherited, siblings may also have the disease. That leaves about a 10 percent chance that a patient will find a suitable donor.
Brodsky's procedure requires just a half-match - meaning that children and parents of the patient could be suitable donors.
Three days after the transplant, the patient is given a high dose of a drug called cyclophosphamide. Just as the bone marrow is taking root, the drug kills off the donor's lymphocytes - blood cells that are part of the immune system.
