By Alison Palkhivala
FLORENCE, ITALY -- May 22, 2007 -- Arsenic trioxide, when used in combination with the anti-CD33 monoclonal antibody cytotoxic agent gemtuzumab ozogamicin, is beneficial both for patients with high-risk myelodysplastic syndrome (MDS) and those with acute myeloid leukaemia (AML), according to research presented here at the 9th International Symposium on Myelodysplastic Syndromes.
Response rates were comparable to rates obtained with induction chemotherapy but were obtained via an outpatient treatment plan, researchers said in a poster session here on May 18th.
"There are a couple of studies that have been published looking at use of arsenic in MDS," said lead investigator Mikkael A. Sekeres, MD, assistant professor of medicine, department of haematological oncology and blood disorders, Cleveland Clinic Taussig Cancer Center, Cleveland, Ohio, United States.
Both studies showed an efficacy rate of about 20% with arsenic trioxide, and efficacy was even higher in patients with lower-risk MDS. Therefore, Dr. Sekeres and colleagues conducted a trial in which they evaluated a combination arsenic trioxide and gemtuzumab ozogamicin (Mylotarg®) in patients with high-risk MDS.
For this multicentre trial, Dr. Sekeres and colleagues enrolled 15 patients with high-risk MDS and 11 with AML and treated them with IV arsenic trioxide 0.25 mg/kg on days 1 to 5 during week 1 and then twice a week on weeks 2 to 12. These patients also received gemtuzumab ozogamicin 3 mg/m2 on day 8 for 1 or 2 12-week cycles. After 12 weeks of therapy, patients with stable disease or improvement, as evidenced by bone marrow biopsy, received another 12-week cycle of treatment followed by another bone marrow biopsy.
Among the 24 evaluable patients, 8 responded to therapy, based on International Working Group (IWG) response criteria for MDS. Three of the ten patients with AML attained partial remission. Six-month survival was 74% and 1-year survival was 32%, which is comparable to what can be achieved with induction chemotherapy for AML, Dr. Sekeres said.
These favourable response rates were obtainable with a comparably short hospital stay.
"The median time in the hospital was 13 days," Dr. Sekeres said. "If you had given these AML folks remission induction chemotherapy, they would have spent a median of somewhere between 28 and 42 days in the hospital. … [So], you can get some decent responses with the combination of arsenic and Mylotarg®, and you can get these responses while treating these older folks as outpatients, and that time not spent in the hospital is probably the most important factor in the therapy that they choose."
[Presentation title: Arsenic Trioxide (ATO) and Gemtuzumab Ozogamicin (GO) in High-Risk MDS Patients or AML Arising From MDS – Updated Data]
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