When some people are first diagnosed with non-Hodgkin lymphoma, the first question that runs through their mind is, “What caused my cancer?” Others wonder whether anything they did contributed to their diagnosis. “Was it something I ate?” “Was I exposed to cancer-causing chemicals while gardening?”
At the biological level, doctors know exactly what causes non-Hodgkin lymphoma. “It’s due to mutations in normal cells,” Dr. Michael Jain, medical oncologist at Moffitt Cancer Center, tells SurvivorNet. DNA changes in healthy infection-fighting white blood cells called lymphocytes cause those cells to transform into lymphoma.
DNA changes in cells happen all the time, and normally the immune system is able to identify those abnormal cells and get rid of them. But if the immune system doesn’t recognize them, or if the abnormal cells multiply too quickly, they can turn into cancer, Dr. Jain adds.
Researchers continue to learn more about the genetic changes that give rise to lymphoma. The information they’re collecting is helping them develop new tests to diagnose this cancer, as well as new treatments.
What they still don’t know for sure is why some people develop non-Hodgkin lymphoma while others don’t. There are a few known risk factors, which include age, family history, and exposure to certain chemicals, but with this cancer there is no one smoking gun. “The data on all of these is not particularly strong. We don’t have anything in lymphoma that’s as good as, for instance, tobacco smoking and lung cancer,” Dr. Jain says.
One of the strongest known risk factors is age. Most patients with non-Hodgkin lymphoma, which accounts for the majority of lymphomas, are diagnosed in their 60s and 70s. There are a few reasons why this cancer tends to emerge later in life. “Number one, you have more of an opportunity for these mutations to occur, these DNA changes,” Dr. Jain says. “Also, the immune system gets a little bit weaker and doesn’t recognize these tumors as well.”
Age is a risk you can’t change. So is your race (white people are more likely to get this cancer than are African Americans and Asian Americans) and your family history.
Other risk factors involve things you’re exposed to, such as viruses. Some viruses have a direct effect on DNA, causing the changes that turn healthy lymphocytes into lymphoma. Viruses that are linked to this cancer include:
Human immunodeficiency virus (HIV), which causes AIDS, can also weaken the immune system to the point where it becomes easier for the cancer to develop. HIV infection is linked to particular types of non-Hodgkin lymphomas, including diffuse large B-cell lymphoma.
But even if you’re infected with one of these viruses doesn’t mean you will absolutely get cancer, Dr. Jain says. “Many people in the population will have these viruses and not get the cancer.”
Some studies have pointed to chemicals such as benzene, the herbicide Agent Orange used during the Vietnam War, and glyphosate — the ingredient in weed killers such as Roundup. Monsanto, the company that makes Roundup, has been on the losing end of several lawsuits from people who developed non-Hodgkin lymphoma after using its product. A 2019 case ended in a $289 million verdict for a 70-year-old man who claimed Roundup caused his cancer. Yet the legal argument for weed killer causing lymphoma is stronger than the scientific one.
“People wonder about things like Roundup or Agent Orange or other exposures that may accelerate the process of forming cancer,” Dr. Jain tells SurvivorNet. “However, I should say that the data on all of these is not particularly strong.”
For lymphoma, the data don’t definitively point to one risk or another as causing the cancer, so it’s hard to assign any blame. These are areas that require more study, Dr. Jain says. For now, it doesn’t hurt to limit your exposure to weed killers and other products containing questionable chemicals. And if you’re worried about your lymphoma risk because of a past exposure, your age, or a family history, ask your doctor if you need extra monitoring.
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