Superior long-term outcomes are achieved when children with acute megakaryocytic leukemia are treated with an allogeneic stem cell transplant during their first remission, according to a recent article published in the journal Blood.

Acute megakaryocytic leukemia (AMKL) is a cancer involving the bone marrow, which is the spongy material inside large bones. The bone marrow produces immature cells that develop into three distinct types of blood cells: red blood cells, which carry oxygen to tissues; white blood cells, which fight infection; and platelets, which aid in blood clotting. AMKL is characterized by excessive division and accumulation of immature platelets in the bone marrow. These cancerous cells never develop into functioning platelets and crowd the bone marrow, causing suppression of normal formation and function of other blood and immune cells. In addition, this cancer is often associated with a condition called myelofibrosis, which occurs when fibrous tissue replaces healthy bone marrow. Children with Down Syndrome appear to have an increased incidence of AMKL, but have a higher survival rate than other patients diagnosed with this disease. Initial standard treatment is chemotherapy, which may produce remissions in a large percentage of patients; however, the majority of patients ultimately experience a recurrence of their cancer.

AMKL is a rare type of leukemia that occurs mainly in adults. Due to the fact that it is such a rare disease, overall data collection has been relatively sparse, making it difficult to determine biological characteristics of patients and responses to treatments for this cancer. Obtaining information to develop statistical associations and trends is important to facilitate the designation of optimal standard treatment.

Recently, researchers at St. Jude Children’s Research Hospital have compiled and evaluated data involving 41 children who were diagnosed and treated for AMKL at their institution. Six of these patients had Down Syndrome, 29 had an original diagnosis of AMKL (de novo), and 6 had a secondary diagnosis of AMKL. The average age was approximately 2 years. Initial treatment with standard chemotherapy produced overall remissions in 60.5% of patients. However, nearly half of these patients experienced a cancer recurrence. Two years following diagnosis, 26% of patients with de novo AMKL who underwent an allogeneic stem cell transplant following initial chemotherapy were alive, compared with 0% following only moderate-dose chemotherapy. Of the patients with de novo AMKL undergoing an allogeneic transplant, 46% were alive 2 years following diagnosis if they received a transplant during remission compared with 0% if they received a transplant when the cancer was still detectable. For all patients, survival at 2 years following diagnosis was 83% for patients with Down Syndrome, 14% for patients with de novo AMKL and 20% for patients with secondary AMKL

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These researchers concluded that treatment outcome is still suboptimal for patients with AMKL in the absence of Down Syndrome. The achievement of an initial remission appears to be the most important prognostic factor. Allogeneic transplantation during remission offers the best chance of cure; however, in the absence of remission, transplantation offers no advantage over chemotherapy alone.

There is still a lot to learn about AMKL, but studies such as these, as well as clinical trials, aid in the future progress of more effective treatments, which potentially lead to increased survival rates. Persons with AMKL may wish to speak with their physicians about the risks and benefits of participating in a clinical trial evaluating stem cell transplantation and other promising new treatment strategies. Two sources of ongoing information regarding clinical trials that can be discussed with a doctor include comprehensive, easy-to-use services provided by the National Cancer Institute (cancer.gov) andeCancerTrials.com. eCancerTrials.com also provides personalized clinical trial searches on behalf of patients. (Blood, Vol. 97, No. 12, pp. 3727-3732, 2001)

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