WASHINGTON — Republican presidential candidate Fred Thompson has a rare type of cancer that specialists say is incurable but not life-threatening.
Although the 65-year-old former senator and actor says his disease is in remission, studies of other cases indicate that it's likely to return within the next two to five years.
But cancer experts say his malignancy — a slow-growing disruption of the immune system known as non-Hodgkin's lymphoma — can be well managed with drugs and needn't interfere with normal activities.
They say Thompson has an excellent chance of survival for at least five to 10 years, based on the experiences of other patients reported in medical journals.
"My understanding is you can expect to live a normal life expectancy,'' Thompson said Sunday on his campaign bus. But he acknowledged that ``it's something that is always potentially there.''
Non-Hodgkin's lymphoma — or non-Hodgkin lymphoma, as the National Cancer Institute calls it — is a type of cancer that begins in the cells of the lymph system, a complex network of specialized cells whose task is to detect and destroy invading microbes.
For unknown reasons, some lymph cells occasionally run amok, traveling through the body and forming cancerous lumps that interfere with the immune system.
Sometimes these unruly cells grow rapidly, causing an ``aggressive'' non-Hodgkin's lymphoma that's often fatal. Sometimes the growth is slow, leading to a case of ``indolent,'' or painless, lymphoma. This is the kind that Thompson has.
The American Cancer Society estimates that 63,130 Americans will be diagnosed with non-Hodgkin's lymphoma this year, and 18,660 deaths will occur. Of the new cases, 81 percent of the patients will be alive after one year, 63 percent after five years and 49 percent will survive for at least 10 years.
Thanks to improvements in treatment, patients are surviving longer than they used to. The five-year expected survival rate of 63 percent is up from 48 percent 30 years ago.
Scientists distinguish at least 30 varieties of non-Hodgkin's lymphoma, some more lethal than others. Thompson's disease is a relatively rare type — a marginal zone lymphoma — that's a subclass of the slow-growing indolent lymphomas.
Indolent lymphomas have a much better prognosis than fast-growing aggressive lymphomas, but they're hard to clear completely from a patient's body.
``Indolent lymphomas such as MZL are almost incurable,'' Dr. David Weissmann, a pathologist and lymphoma expert at Robert Wood Johnson University Hospital in New Brunswick, N.J., said in an e-mail message. ``The good (?) news is that they take a long time to kill a patient. The bad news is that there is almost no hope of a permanent cure.''
``I would suspect that he (Thompson) will at some point have a recurrence of his disease,'' said Dr. Corey Cutler, a hematologist at the Dana Farber Cancer Institute in Boston. ``The majority of MZL is not curable.''
Because MZL is so rare, there have been few studies of patients' outcomes.
In a group of 27 MZL patients, 21 of them, or 79 percent , were alive after five years, but all but six of them — 22 percent — had relapses.
Another group of 424 MZL patients enjoyed a five-year survival rate of 86 percent to 95 percent, but the cancer had returned in half of them during that time.
Thompson's cancer was detected in 2004, as a lump in his neck. It later spread to his groin and other areas. His doctor prescribed a new drug, Rituxan, which drove the disease into remission.
In many cancers, a spread from the original site to other organs is an ominous sign. That isn't necessarily the case with lymphoma, however.
``The fact that it was present in multiple nodes at one time is commonplace and does not dramatically affect outcome,'' Cutler said.
For a tutorial on non-Hodgkin's lymphoma, go to http://pleiad.umdnj.edu/hemepath