Although non-Hodgkin's lymphoma like that contracted by Jacqueline Kennedy Onassis is normally considered one of the more curable cancers, nearly half of those who develop it die within five years.
"Even in the best of (treatment) programs, one-third of patients don't respond well, and two-thirds ultimately die of the disease," said Dr. Rex Greene, chief of the cancer teaching program at Huntington Memorial Hospital in Pasadena.
And if the initial treatment is not successful, the disease can progress rapidly. "That's the nature of lymphoma. It's especially aggressive," Greene said. Because chemotherapy targets rapidly dividing cells, it is often successful against lymphomas, which are fast-growing cancers.
"But if they don't respond to treatment, they can come roaring back," Greene said. "Some lymphomas can double in size in the space of a couple of weeks."
Mrs. Onassis' cancer was diagnosed in January and she was hospitalized most recently at the beginning of the week for what was described as complications of the therapy. A hospital spokesman announced Thursday that all treatment had been halted and she had returned home.
Non-Hodgkin's lymphoma is a cancer of the immune system--specifically the lymph nodes and the lymphocytes, cells that protect the body against invading bacteria.
The incidence has been rising, reaching about 43,000 a year, because the disease is relatively common in AIDS patients, organ transplant recipients and other people whose immune systems have been suppressed. An estimated 21,200 people will die of it this year, according to the American Cancer Society.
The disease most commonly strikes people over 50 and, for unknown reasons, is becoming increasingly common among those over 65. It is somewhat more common in men than in women.
The characteristic symptoms of lymphoma are enlarged lymph nodes, anemia, weight loss and fever. There is generally little pain. Among AIDS victims and transplant patients, the most common cause is the Epstein-Barr virus, which also causes mononucleosis. It is also believed to be caused by exposure to industrial chemicals and pesticides, which may be why it is more common among farmers.
"But for any individual case, we generally don't know the exact cause," said Dr. Cary Presant, an oncologist who is president of the California section of the American Cancer Society.
The complications of lymphoma treatment include low white cell counts, bleeding, infections, nausea, diarrhea and general gastrointestinal discomfort.
"These are very toxic medications we use to treat it," Greene said. "When they don't work, we have the side effects of chemotherapy on top of the direct effects of the tumor--a potent combination. With a fast-growing cancer, it is hard to distinguish which is causing which problem."