Arsenic trioxide shows promise as a treatment for men whose prostate cancer has not responded to standard therapies, according to results of a phase II clinical trial presented at Chemotherapy Foundation Symposium XX.

The American researchers studied the effectiveness and safety of the experimental treatment in 15 patients with prostate cancer: Eligible patients had failed at least 2 hormonal treatments, may have had prior chemotherapy or radiation therapy, or had undergone multiple forms of treatment.

The researchers found the treatment appeared to benefit 2 patients. In particular, 1 patient who was receiving radiation therapy at the same time as the experimental therapy had an extremely sharp decrease in his blood level of prostate specific antigen.

"We had promising results in 2 patients in our study," said Robert E. Gallagher, M.D., lead author, "but expanded studies are needed to determine the effectiveness of the arsenic treatment in larger populations."

Arsenic has already proved to have a "remarkable clinical effectiveness" in patients with relapsed acute promyelocytic leukemia, according to Gallagher.