They’re good cells gone bad
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% 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, re-emerge 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.
