While the results were described as promising, it's not known yet whether the novel approach will be superior to the standard early treatments normally used for a slow-growing but incurable type of non-Hodgkin's lymphoma.
"The striking thing about it is how such a short treatment can produce such long-lasting remissions," said Dr. Mark S. Kaminski, who developed the new treatment, Bexxar, with a University of Michigan colleague.
The researchers said more studies will be needed to determine whether doctors should use Bexxar as a first treatment to fight the immune-system cancer. Bexxar is currently only approved for use when other therapies, including chemotherapy and radiation, fail.
Bexxar treatment starts with a test dose followed by a full dose a week later instead of over months, as with chemotherapy. One advantage is fewer side effects, such as hair loss, the researchers said.
The findings reported in Thursday's New England Journal of Medicine were partly funded by drug maker Corixa, which recently sold the rights to Bexxar to GlaxoSmithKline. Some of the scientists have received fees from the drug makers; one was a Corixa employee. The university holds patents for Bexxar, and Kaminski and his co-inventor share in royalties.
Dr. Joseph M. Connors, of the British Columbia Cancer Agency in Vancouver, said the results were impressive even though they involved carefully chosen patients and no comparison group.
"This is quite promising and firmly indicates that we need to know what would happen in comparisons to standard treatment" said Connors, who wrote an accompanying editorial.
The Michigan researchers tested Bexxar in 76 patients with advanced follicular lymphoma who had received no other treatment. Follicular lymphoma strikes about 15,000 adults in North America each year. Patients typically survive seven to 10 years.
The approach used in Bexxar, called radioimmunotherapy, delivers lethal radiation directly to cancer cells. The method is being tested in other types of cancers, and Bexxar and another treatment called Zevalin are approved for advanced non-Hodgkin's lymphoma. In Bexxar, radioactive iodine-131 is attached to antibodies that target and kill lymphoma cells.
In the study, 72 patients or 95 percent had some shrinkage of their tumors after getting Bexxar. The cancer disappeared in 57 participants (75 percent), and three-quarters of them were still disease-free after five years. Many remained cancer-free until the end of the study, a maximum of about eight years. The researchers are continuing to follow the participants.
The most common side effect was a brief drop in white blood cells. Nine patients died, six from lymphoma.