doc_text: The results need to be replicated by other researchers before definitive conclusions can be made, and the long-term effect of the treatment remains unknown.
  But the initial experience with the compound is especially promising, and an apparent improvement over other therapy for the disease, scientists said.
  "There aren't many {drugs} where you can administer one course of treatment and have the disease go away and stay away for as long as four years," says Lawrence Piro, chief of cancer research at Scripps Clinic &amp; Research Foundation, La Jolla, Calif., where the drug was developed.
  "The leukemia hasn't come back in any of the patients we treated."
  The study is published in today's New England Journal of Medicine.
  "It is without doubt the most effective treatment for hairy-cell leukemia, in terms of rapidity of response," adds Elihu H. Estey, a cancer researcher at the University of Texas-M.D. Anderson Cancer Center, Houston.
  Dr. Estey recently began treating patients with 2-CdA and has had similar results with five patients.
  "It's a striking finding," he says.
  "It's very unlikely to be a fluke."
  Hairy-cell leukemia, so-called because of the appearance of the cancerous cells under the microscope, affects about 6,000 people in the U.S., with 600 new cases a year.
  As the disease progresses, patients become anemic, are vulnerable to infection and often need blood transfusions.
  Until the mid-1980s, treatments were ineffective, and patients often died of blood problems and infections.
  Since then, alpha interferon, a drug sold by Hoffmann-La Roche Inc. and Schering-Plough Corp. and an experimental drug called deoxycoformycin have significantly reduced death rates from hairy-cell leukemia.
  Hoffmann-La Roche is the U.S. subsidiary of F. Hoffmann-La Roche &amp; Co. of Switzerland.
  But neither drug is as effective as 2-CdA appears to be in low doses and both can cause such side effects as nausea, vomiting, skin rashes and nervous-system disorders, researchers say.
  "With the lack of toxicity and the ease with which people go into remission {with 2-CdA}, I think there's something really going on here," says Ellin Berman, a staff leukemia doctor at Memorial Sloan Kettering Cancer Center, New York.
  Scripps said it negotiated an agreement with a subsidiary of Johnson &amp; Johnson, New Brunswick, N.J., to produce and distribute 2-CdA to other centers for broader clinical trials.
  The researchers said the drug is easy to produce and thus is likely to be less expensive than other cancer treatments.
  In the 12-patient study, 2-CdA, short for 2-chlorodeoxyadenosine, was administered continuously for seven days to patients aged 36 to 61.
  Within eight to 10 weeks, 11 of the patients had no trace of cancer in their blood or bone marrow; the 12th had a small amount remaining in the marrow, but he declined further bone marrow monitoring, Dr. Piro said.
  His blood tests are normal, Dr. Piro added.
  None of the patients have had a relapse; complete remission has lasted from seven to 46 months after treatment, according to the study.
  "When you can make all the disease go away with a single infusion of therapy, you have a disease which may be able to be cured," Dr. Piro said.
  But because hairy-cell leukemia proliferates slowly, a relapse could occur long after treatment.
  Longer follow-up is necessary to determine whether 2-CdA actually cures the disease.
  The drug was first made about 10 years ago at Scripps by Dennis A. Carson, who studied severe combined immunodeficiency disease, made famous a few years ago by the Texas boy that lived in a bubble.
  People with that disease lack an enzyme that processes deoxyadenosine, a chemical that, without the enzyme, builds up in infection-fighting white blood cells and kills them.
  Since cancer patients have the enzyme, Scripps scientists developed a compound that mimics deoxyadenosine, but tricks the enzyme so it can't be processed.
  The compound then kills the white blood cells, including those that are cancerous.
  New, normal white cells are then generated in the bone marrow.
  Because hairy-cell leukemia is rare, a 12-patient study "is considered a pretty good series," says Sloan-Kettering's Dr. Berman.
  "It's ironic that we have three active drugs for a disease that's fairly rare, but for some of the more common forms of leukemia, we don't yet have good treatments."
  Dr. Piro said 2-CdA has also been used effectively in initial trials to treat more common cancers, including chronic lymphocytic leukemia, non-Hodgkins lymphoma and cutaneous T-cell lymphoma.
  About 50% to 60% of patients -- most of whom had failed other treatments -- responded to the drug, some with complete remission, he said.
  "Now, we will use {2-CdA} as a first treatment to see if response and remission are higher," he said.
  Meanwhile, researchers at University of California at San Francisco are testing 2-CdA on AIDS-related lymphoma.
summary_text: A new cancer drug called 2-CdA proved nearly 100% effective treating 12 patients with hairy cell leukemia.
  The patients underwent just a seven day treatment and suffered almost none of the usual debilitating side effects associated with chemotherapy, yet, they have been disease free for four years.
  Results must be replicated by other researchers before definitive conclusions can be made.
  The drug is easy to produce and likely to be less expensive.
  Dr. Lawrence Piro of the Scripps Clinic and Research Foundation said it has also been used effectively in initial trials to treat more common forms of leukemia.