Doctors studying a common type of tumor at the Harvard-affiliated Dana Farber Cancer Institute have developed a treatment that has yielded encouraging preliminary results, according to reports published in today's New England Journal of Medicine.

The new treatment for non-Hodgkins lymphoma involves taking bone marrow out of patients while they undergo chemotherapy and radiation, and then replacing the marrow after it is treated with a special antibody the researchers developed.

Of the 49 patients treated in the Dana Farber study, 65 percent are now disease-free, with several of them out of treatment for as long as five years. The mortality rate in the study was less than 5 percent, far lower than the approximately 75 percent death rate of other types of treatment, said Dr. Lee M. Nadler, one of the 12 researchers.

Lymphoma is the seventh most common cause of death from cancer in the United States, according to medical publications. Non-Hodgkins lymphoma, the subject of the Harvard study, is the most common tumor of humans between the ages of 20 and 40, and there are more than 25,000 new cases of it every year, Nadler said.

He said one of the most important aspects of the new treatment was that it could be applied in the future to patients with recently-diagnosed cases of the lymphoma. Usually lymphoma treatments using bone marrow transplants have been applied only to patients who have experienced a relapse of the disease.

"The most important thing is not the present success for relapse patients," but rather that marrow treatment might now be legitimately used in "primary treatment of non-Hodgkins lymphoma," Nadler said.

The Dana Farber study has a high survival rate in part because of the methods the researchers used to select the patients treated with the new treatment. "Selecting the patients leads to a very low mortality rate and very high success rate," Nadler said.

The patients used in the study were otherwise healthy and all of them were somewhat responsive to conventional types of therapy, such as chemotherapy, he said.

In the treatment the doctors used, the patient is first given chemotherapy, in order to lessen the number of the tumor cells. Next, the doctors removed one-fifth of the patient's bone marrow through needles.

In the laboratory, the doctors treated the marrow with B-1, an antibody that kills the tumor cells. The doctors then froze the marrow at -196 degrees Celsius, enabling it to live for an indefinite amount of time.

They then treated the patients with intense chemotherapy, and then gave them high levels of irradiation, to ensure that the cancerous bone marrow would not return. Afterwards, the treated marrow was thawed and given back to the patients intravenously, Nadler said.