Rate of stem cell transplants among African-Americans lower

Feb 11 2007

Lower transplant rates in ethnic communities may be explained somewhat by a lack of suitable anonymous donors, a problem the medical community has long known and been working to address. Surprisingly, the study found the discrepancy in treatment held true even when the transplant was autologous (e.g. self-donated stem cells were used) or when the cells were donated by a relative, typically a sibling.

"The National Marrow Donor Program has made great strides in increasing the number of African-American donors, which is important because non-related donors are more likely to have a tissue type that matches the patient if they are of the same ethnic group," said Mary Horowitz, M.D., M.S., chief scientific director for the Center for International Blood and Marrow Transplant Research (CIBMTR) and professor of medicine at the Medical College of Wisconsin, Milwaukee. "But our research shows the problem is more extensive than we thought, and if all we do is increase the number of available anonymous donors, we won't be successful in making sure that everyone who needs transplant gets one. While the shortage of appropriate anonymous donors is an understandable cause of a lower rate of unrelated donor transplantation, it should not affect the use of autologous or related donor transplants in African-Americans, yet the rates of these transplants are also lower."

Stem cell transplant (also known as blood and marrow transplant) is used to treat diseases of the blood and several types of cancer. In the study, researchers looked at the rate of stem cell transplants among African-Americans, Caucasians and men and women for the treatment of three types of cancer most commonly treated with stem cell transplants: leukemia, lymphoma and multiple myeloma. Together, these cancers account for nearly 10 percent of all cancer cases in the United States.

Patients who are candidates for stem cell transplants are most likely to find a matching donor in someone of their own ethnicity. The group of genes known as human leukocyte antigens (HLA) in the donor and patient must be closely matched for the procedure to be successful, and that is more likely to be true within ethnic groups. Because African-Americans have a greater variation of HLA types, it is estimated that three times as many African-American donors are needed to equal the chance of obtaining a Caucasian match, according to the National Cord Blood Program.

The next step is for researchers to determine why the stem cell transplant self-donation and relative-donation rates differ between Caucasians and African-Americans. Among the potential reasons:

• Differences in insurance coverage for sophisticated or aggressive health care treatments, including stem cell transplants
• The effect of cultural attitudes toward the medical system
• Physicians attitudes toward minorities
• Bias among doctors and patients; for instance, doctors may make assumptions about how different communities feel about aggressive therapy, including stem cell transplants

"The National Marrow Donor Program and the Center for International Blood and Marrow Transplant Research are interested in exploring the reasons for the discrepancy, and may conduct focus groups regarding barriers to participation in transplantation among minorities," said J. Douglas Rizzo, M.D. M.S., associate scientific director of CIBMTR and associate professor of medicine at the Medical College of Wisconsin.

The study also looked at gender differences and although men were somewhat more likely than women to receive autologous stem-cell transplants, the difference wasn't striking and may be just a statistical anomaly, said Dr. Horowitz.

Previous studies have shown that African-Americans are more likely to be diagnosed at advanced stages of cancer and less likely to receive optimal care than Caucasians.

Stem cells are progenitor cells in the bone marrow and blood stream, meaning they can develop into a number of different cell types. Stem cells can be damaged by disease, such as cancer, or treatment, such as chemotherapy or radiation. Stem cell transplant involves taking the cells from healthy donors and infusing them in the ill patient, where they can reproduce more healthy stem cells and strengthen the patient's immune system. Stem cells may be collected, or harvested, directly from the bone marrow, or from the circulating blood and infused into the patient's bloodstream. In addition to being donated anonymously or by a relative, stem cells can sometimes be self-donated. That is, they are removed from the patient, conditioned, and reinfused in the patient after chemotherapy or other stem cell-destroying treatment.