BOSTON -- Contrary to their earlier assurances, Paul E. Tsongas' doctors now say that he suffered a recurrence of lymphoma in 1987, less than a year after undergoing an experimental bone marrow transplant, and was treated with an additional course of radiation for the cancer.
Mr. Tsongas said in an interview Monday that he did not recall his doctors saying that a biopsy of a lymph node from his armpit in the summer of 1987 showed cancer, as the doctors say they did.
Mr. Tsongas, who is the first known cancer survivor to run for president, has remained free of lymphoma, a cancer of the immune system, for five years. Two doctors who treated him at the Dana-Farber Cancer Institute in Boston have said that, if elected, Mr. Tsongas had a favorable prognosis for living out his term and that his health was not a factor in the suspension last month of his campaign for the Democratic nomination for president.
Saying that the recurrence did not affect the former senator's prognosis, one of the Dana-Farber doctors said he had not mentioned the additional treatment in earlier interviews because was not important and the other said he had forgotten about it.
But experts not connected with Mr. Tsongas' case said that the new details could alter the favorable prognosis that his doctors spoke of during the campaign.
"The significance of a relapse after a bone marrow transplant is huge because it means that the bone marrow transplant did not cure him," said Dr. James O. Armitage, a lymphoma expert at the University of Nebraska in Omaha.
Cures of the type of lymphoma suffered by Mr. Tsongas are rare incases in which a recurrence follows a bone marrow transplant, the experts said.
Until the new disclosures, which came to light after further inquiries by the New York Times about Mr. Tsongas' condition, the doctors had said Mr. Tsongas had been free of disease since the transplant in 1986.
Mr. Tsongas' personal physician, Dr. Tak Takvorian, who cared for Mr. Tsongas during and after his bone marrow transplant, said his team told Mr. Tsongas the biopsy of the lymph node showed lymphoma. "We never do otherwise," Dr. Takvorian said. "He wasn't being duped."
Mr. Tsongas said that as he recalled it, there was a dispute among the doctors about the biopsy results. He did not recall their saying it was indeed lymphoma and said they decided to give extra radiation treatments as a preventive measure.
When he was on the campaign trail, Mr. Tsongas repeatedly spoke about his triumph over cancer. He gave his doctors permission to discuss his medical history, which they did. But his doctors and the Dana-Farber Cancer Institute, a Harvard teaching hospital, now acknowledge that they have not told the complete story.
Dr. Takvorian, who was an ardent supporter of Mr. Tsongas' campaign and who had Tsongas campaign posters in his office, said in a recent interview that he had not disclosed all the details of Mr. Tsongas' medical history in a three-hour interview in February because it would take too much time, was not relevant and was of little interest.
Dr. Takvorian also said he advised Mr. Tsongas not to provide the voluminous pages of his medical records to reporters, and those records were not released. One reason, the doctor said, was that medical thinking about the treatment for lymphoma had changed significantly in recent years and that certain early statements could be misread if they were taken out of context.
In an interview on Feb. 25, Dr. David M. Livingston, Dana-Farber's head doctor, and Dr. Lee M. Nadler, a researcher who headed the lymphoma study described in the medical journal report, adamantly refused to discuss details of Mr. Tsongas' case on grounds that it would violate patient-doctor confidentiality.