Researchers from the University of Pittsburgh have reported that single-agent Mylotarg® (gemtuzumab ozogamicin) results in a complete remission (CR) rate of 30% in patients 70 years or older with newly diagnosed acute myeloid leukemia (AML). The details of this study were published early online in Cancer on March 30, 2010.1

The median age for patients with AML is now 67-70 years. Treatment of elderly patients with AML remains unsatisfactory, and most patients die within a few months of diagnosis. One of the reasons for the dismal prognosis is the association with adverse cytogenetic and molecular abnormalities. Another reason is the presence of significant co-morbidities in many patients that precludes intensive induction and consolidation therapies.

Mylotarg is a monoclonal antibody linked to a toxin called calicheamycin. The monoclonal antibody is directed at CD33, which is present in 80-90% of AML cells but is not present on the normal hematopoietic stem cell. Thus, the antibody-toxin conjugate can selectively kill leukemia cells. The primary toxicity of this agent is veno-occlusive disease (VOD) of the liver, presumably because there are CD33 positive cells in the liver. Mylotarg was approved by the U.S. Food and Drug Administration in 2000 for the treatment of patients with AML over the age of 60 who had failed initial treatment.

The current study involved 49 patients with newly diagnosed AML 70 years of age or older treated with single-agent Mylotarg. All were deemed unsuitable for treatment with standard intensive combination chemotherapy.

• The complete response (CR) rate was 14% for all treated patients.
• The CR rate was 30% for patients with intermediate-risk cytogenetics.
• The CR rate was 0% for patients with adverse cytogenetics.
• Median survival was 3.7 months for all patients.
• Median survival for patients achieving a CR was 11.8 months.

These authors suggest that single-agent Mylotarg was a treatment option for older patients with intermediate-risk AML.

Comments: This study emphasizes the continued problem of treatment of older patients with AML.

Reference:

1 McHayleh W, Foon K, Redner R, et al. Gemtuzumab ozogamicin as first-line treatment in patients aged 70 years or older with acute myeloid leukemia. Cancer [early online publication]. March 30, 2010.