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ON April
11, actor and former Sen. Fred Thompson, a prospective
Republican presidential candidate, announced he had a
form of cancer (now in remission) called indolent
lymphoma. To learn more about this disease, we spoke
with Dr. Mark Kirschbaum, director of new drug
development at the City of Hope Comprehensive Cancer
Center in Duarte.
What’s
lymphoma?
Lymphomas are cancers that arise in lymph nodes,
housecleaning glands that filter blood and clean out
bacteria and viruses. The lymph node cells, or
lymphocytes, “are like firemen sitting around waiting
for an emergency,” Kirschbaum says. When an emergency
arises, such as a bacterial infection, the cells get to
work and reproduce many, many times. “Their job is to
take out the bacteria, and then turn off and stop
growing and killing. But sometimes something goes
wrong,” he says. “Somehow, in the millions of cells that
do that, one has figured out how to not turn off
afterward.” And that cell spawns the cancer.
Different news reports of Thompson’s cancer called it a
multitude of names: malignant lymphoma, indolent
lymphoma and marginal zone lymphoma. Are these all the
same thing?
Basically, yes, Kirschbaum says. Marginal zone lymphomas
reside in the lymph nodes that are strung along the
gastrointestinal tract, from the mouth to the rectum.
They account for about 8 percent of all lymphomas.
All marginal zone lymphomas are known as
“indolent”—meaning they grow very slowly. But they’re
also malignant, meaning they have genetic mutations that
allow them to bypass cellular signals that tell them to
stop multiplying. “They don’t grow rapidly, but at the
same time they are almost impossible to kill,”
Kirschbaum says.
How is
lymphoma treated?
Some
marginal zone lymphomas—such as those in the stomach—are
constantly stimulated by a particular, chronic bacterial
infection. Often, getting rid of the bacteria with
antibiotics stops the cancer growth, and it goes into
remission.
If the
marginal zone lymphoma forms a compact growth, such as
in Thompson’s case, radiation directed just at the lump
can kill off many of the sluggish cancer cells.
Chemotherapy can also be used to treat lymphoma.
Immunotherapy, wherein antibody injections are used to
quell the cells, is a popular way to treat indolent
lymphoma. An antibody targeted to a protein on the
surface of the cancerous cells—the cancer’s so-called
“address”—can kill them.
Some
marginal zone lymphomas are left to themselves, and
doctors watch and wait. “In these cases, physicians
usually don’t do anything with them unless there’s pain,
or changes in how many lymphocytes are in the blood,”
Kirschbaum says. “People live very long lives. The
lymphomas frequently don’t interfere with daily life.”
Kirschbaum and others are investigating new treatments
called molecular therapies, currently in early clinical
trials, that seek to reprogram the cancer cells by
fixing their broken off-switch. “Rather than
cell-killing agents, molecular therapies teach the
lymphoma cells the proper way to live,” he says.
What
causes relapse?
Some
diseases, such as shingles, reemerge when people are
under stress. Could the stress of a White House run or
even the presidency cause the cancer to flare up? Not
likely, Kirschbaum says. No one knows what causes the
cancer cells to start growing again, but stress is
probably not a factor. According to the National Cancer
Institute, relapses are more likely to occur within a
couple of years of treatment. |