Arsenic Induces Remissions in Patients With Acute Promyelocytic Leukemia

Arsenic may be on the verge of overcoming its bad reputation. Two years ago, Chinese researchers reported that low doses of arsenic trioxide induce remission in patients with acute promyelocytic leukemia (APL), prompting physicians in the West to undertake their own pilot study.

Researchers at Memorial Sloan-Kettering Cancer Center have now become the first western investigators in the to show that arsenic effectively induces remission in patients who have relapsed with APL. The findings were reported in the New England Journal of Medicine.

“We now know that arsenic can safely bring patients with APL into remission, which may ultimately give them a second chance at life,” said Dr. Raymond P. Warrell, Jr, senior author of the study and a leukemia specialist at Memorial Sloan-Kettering Cancer Center.

Arsenic Provides a Second Chance at Life

In the pilot study, 12 patients who had relapsed after conventional therapy were treated with low doses of arsenic trioxide. Of the 12 patients, 11 achieved remission anywhere from 12 to 39 days after arsenic treatment began, experiencing only mild side effects. The single patient who did not go into remission died from a complication related to the disease 5 days after arsenic treatment was initiated and could not be evaluated in the study.

Once remission was achieved, each patient stopped treatment briefly, then resumed repeat courses of arsenic trioxide therapy every 3 to 6 weeks, thereafter. After two cycles of therapy, investigators conducted additional tests to determine whether any molecular evidence of leukemia remained. Three patients tested positive for disease and later relapsed with APL, while eight patients tested negative and remained in remissions for as long as 10 months. To date, several patients have received up to six courses of arsenic treatment without experiencing cumulative side effects.

Expanded Role for Arsenic

“Based on these highly sensitive molecular results, treatment with arsenic trioxide appears to exceed the effectiveness of any single drug used to treat APL,” said Dr. Steven Soignet, lead author of the study. “Still, this is not a cure. More studies will tell us how truly effective arsenic trioxide will be over the long term.”

 “This finding shows that arsenic trioxide does not discriminate between APL that is resistant or not resistant to retinoic acid, which may mean that we can use it at the outset of treatment for patients with APL,” said Dr. Soignet.

Clinical trials using arsenic trioxide to treat patients with APL are ongoing at Memorial Sloan-Kettering and several other centers throughout the country. Investigators will next look at the effectiveness of arsenic trioxide in treating other types of cancers.