Beyond Chemotherapy

It'

s hard not to get excited about an experimental cancer drug that shows real promise fighting chronic myeloid leukemia. The standard treatments for this rare disease--chemotherapy and interferon--are pretty tough on the body. Bone-marrow transplants can lead to a cure, but even patients with a perfectly matched donor face a 20% risk of dying in the first six months after the procedure.

So there was plenty to celebrate last week when the first articles on a new drug called Glivec appeared in the New England Journal of Medicine. They reported that the drug kills leukemia cells (and only leukemia cells) with very few side effects. Television anchors breathlessly reported a "revolutionary" treatment for cancer and called Glivec a "miracle drug."

But the studies' authors--at Oregon Health Sciences University and the drug company Novartis--still have a lot to prove. The current reports are from what researchers call Phase I, or safety, studies, which are designed to test a drug's side effects, not its ability to prolong lives. Several patients developed severe though reversible anemia while on the drug, and there's a strong possibility that cancer cells could eventually develop resistance.

Still, there is reason to be cautiously optimistic. Chronic myeloid leukemia occurs as the result of a single genetic accident. By blocking the wayward protein that is formed as a result, Glivec tricks the leukemic cells into, in essence, committing suicide. (Normal white blood cells soon take their place.) So far, 51 of 53 patients who received the highest dose of the drug in one of the studies have gone into remission. In seven of those cases doctors can no longer detect any cancer-causing genetic abnormalities.

Researchers at the Dana-Farber Cancer Institute in the U.S. and the Helsinki and Turku Universities in Finland are already trying Glivec on a rare abdominal cancer called GIST (for gastrointestinal stromal tumor). More common malignancies, such as cancers of the breast and colon, arise as a result of several genetic accidents and so are unlikely to respond to Glivec. But at the very least, the drug's preliminary successes have given cancer researchers promising avenues to pursue. And sometimes that's all you can ask for.