Allogeneic Stem Cells Effective in AML Treatment for Younger Patients

Cancer Consultants, July 6, 2007

Unrelated allogeneic stem cell transplant may benefit patients with AML who are at a high risk of developing cancer progression following standard therapy according to a recent article published in the journal Blood.

Characterized by the rapid, uncontrolled growth of immature white blood cells known as myelocytes, acute myeloid leukemia (AML) is a cancer of the bone marrow and blood. The average age of diagnosis is more than 65 year old, although anyone young or old can develop the condition.

Defined as the disappearance of leukemia cells in the bone marrow and normalization of the red blood cell, white blood cell, and platelet levels, the goal is to achieve remission with a treatment protocol consisting of induction therapy (initial treatment) that includes chemotherapy. In order to reduce the likelihood of leukemia recurrence, patients generally receive additional treatment (consolidation therapy) following their completion of the induction therapy. Consolidation therapy can range from less aggressive to extremely aggressive depending on the patient's existing medical conditions, age, or prognosis of the leukemia.

Involving the use of high doses of therapy, which kill a greater amount of cancer cells than standard doses, an allogeneic stem cell transplant is considered an extremely aggressive treatment option. The patient's susceptibility to the need for blood transfusions, bleeding, and infection, is increased by the high doses of therapy which cause a significant reduction in blood cells. Life-threatening infections can be a result of these high doses of therapy.

Following high-dose therapy, stem cells are collected from a donor and infused into the patient to restore the levels of blood cells. Stem cells are immature blood cells. The patient's cancer cells can also be attacked by these donor stem cells. A potentially life-threatening condition called graft-versus-host disease (GVHD) can also be caused by the donor cells since there is a chance that they can attack a patient’s healthy cells as well. Unrelated donors tend to have a higher risk of developing GVHD than patients who use cells that are donated by somebody that is a blood relative.

Researchers have focused on curative options that are more easily tolerated since the treatment-related mortality and side effects can be substantial in allogeneic stem cell transplant. Despite these factors, an allogeneic stem cell transplant still appears to provide optimal outcomes for patients who are younger or those with very aggressive AML.

To evaluate the use of allogeneic stem cell transplants with unrelated donors for patients with AML, a clinical study was conducted by researchers affiliated with the International Blood and Marrow Transplant Registry. This trial included 261 patients with AML in first remission (the first time following treatment that disease is undetectable) or second remission (the second time following two different treatment courses the disease is undetectable) who were 60 years of age or younger. Patients in this trial were divided into three groups: those who had a high , intermediate or low risk of developing a cancer recurrence following standard therapies.

Patients in first remission produced the following results:

• At 5 years, for all groups of patients the overall survival was between 29%-30%.

• At 5 years, mortality related to treatment was 63% for patients at a low risk of developing a recurrence, 53% for patients at an intermediate risk of developing a recurrence, and 47% for patients at a high risk of developing a recurrence.

• Cancer recurrence rates were 8%, 17% and 26%, respectively for patients with low, intermediate and high risks of developing a cancer recurrence.

Patients in second remission produced the following results:

• At 5 years, among patients with a low, intermediate and high risk of developing a cancer recurrence the overall survival was 45%, 37% and 36%, respectively.

• At 5 years, among patients with a low, intermediate and high risk of developing a cancer recurrence the mortality related to treatment was 46%, 46% and 30%, respectively.

• Cancer recurrence rates among patients with a low, intermediate and high risk of developing a cancer recurrence were 12%, 18% and 32%, respectively.

The researchers concluded that patients who have a high risk of a cancer recurrence, in first remission with AML, and aged 60 years or younger can achieve an overall survival rate comparable to those among patients with a lower risk of a recurrence at 5 years from an unrelated allogeneic stem cell transplant. Patients in their second remission did not follow the same trend. The mortality rate associated with the treatment also remained high.

A stem cell transplant may be a good option for those patients who do not have a related donor for an allogeneic stem cell transplant, are at a high risk of developing a cancer recurrence, and have AML. These patients may wish to discuss stem cell treatment as a possible option.