CORRECTED - If it doesn't kill you: Arsenic helps in cancer

(Corrects name of drug maker in sixth paragraph to Cephalon Inc.)

By Julie Steenhuysen

CHICAGO, June 2 (Reuters) - Arsenic, the poison of choice for many a murder mystery, can significantly extend survival in patients with a rare form of leukemia, U.S. researchers said on Saturday.

"It's a much smaller dose than you would use to poison people," added Dr. Bayard Powell of Wake Forest University Baptist Medical Center.

Adding arsenic to standard treatment can extend patients' lives and prevent relapse, Powell said. And the effect is so impressive that patients may some day be able to skip chemotherapy -- but that will take more testing.

"This study has redefined the standard of care," said Powell, who presented results from the large, three-year study at a meeting of the American Society of Clinical Oncology in Chicago.

"The people who took arsenic lived longer," Dr. Nancy Davidson, president-elect of the American Society of Clinical Oncology, told Reuters.

The drug, arsenic trioxide, which is made by Pennsylvania based Cephalon Inc. (CEPH.O: Quote, Profile, Research) and sold under the brand Trisenox, is approved for people with acute promyelocytic leukemia, or APL, whose disease has returned.

Standard treatment for APL -- a form of acute myeloid leukemia that strikes 1,500 people a year in the United States -- involves chemotherapy and a form of vitamin A called all-trans retinoic acid, which helps 70 to 80 percent of patients gain long-term remission.