You know by now that cigarette smoking is the No. 1 risk factor for lung cancer. “About 85 percent of lung cancer diagnoses are in current and former smokers,” says Dr. David Gerber, associate professor of internal medicine and clinical sciences at UT Southwestern Medical Center.
What Happens When You Smoke?
“There are so many chemicals in tobacco smoke that may be associated with cancer,” Gerber says. “About 20 carcinogens [substances that cause mutations in cells] have repeatedly been shown to be linked to lung cancer.”
When you inhale cigarette smoke, your body handles the toxins in one of two ways, Gerber says. It can detoxify the toxins and clear them out of your body (for example, through your urine). Some people process toxins and get them out of the body faster than others. If you can’t detoxify the carcinogens, they interact directly with your DNA, the command center of each cell.
When something damages a healthy cell, the cell divides to repair the damage. Once the damage is repaired, it stops dividing. That’s normal cell repair, says Dr. James Davis, medical director at the Duke Center for Smoking Cessation. “A cancer cell, on the other hand, doesn’t know when to stop dividing. Normally, a cell in the lung or another organ knows exactly what to do. Each cell has its function within the organ. A cancer cell loses the ‘understanding’ that it is part of a larger structure and divides in an unchecked way. A cell can become cancerous if it develops specific mutations and loses its ability to recognize when to stop growing.”
Just as people process carcinogens differently, the rate of repair of damaged DNA varies from one person to the next. Some populations are good at repairing damage and getting rid of carcinogens. These differences are part of the reason some smokers develop lung cancer and others don’t. It can take many years of cell changes before a patient clinically presents with lung cancer.
[See: What Not to Say to Someone With Lung Cancer.]
What Are the Risks?
A study that examined smoking-related mutations found that for every 50 cigarettes you smoke, it caused one mutation in every cell in the lungs, Davis says. “The link between the mutations and cancer is a little like rolling the dice, but the odds get a little worse each time you smoke,” Davis says. “As you smoke, you will get more and more mutations. At some point, one of the mutations will be the wrong one — the kind that causes cancer. If someone is a heavy smoker and they don’t have cancer, mostly, they’ve just been lucky.”
Smoking also causes inflammation. “Inflammation is actually a normal part of healing,” Davis says. It produces cytokines, chemical messengers that help repair tissue after an injury. These cytokines dilate blood vessels and allow repair cells to get into the area to clean up damaged tissue. Tissues can get red and swollen because healing is taking place.
“Paradoxically, inflammation in the lungs that occurs due to smoking actually increases our chances of getting cancer,” Davis says. “When smoking causes inflammation in the lungs — as it always does — the inflammatory response increases damage to our DNA, making cancer more likely. In short, because smoking leads to mutations and inflammation in the lungs, it’s a ‘perfect storm’ for causing cancer.”
This genetic damage occurs throughout the genome, according to researchers at Dana-Farber Cancer Institute. It’s just as likely to occur in a cancer-related gene than not. However, the researchers say, because smoking causes damage indiscriminately, it increases the chance that mutations will arise in cancer-linked genes.
[See: 7 Things You Didn’t Know About Lung Cancer.]
The Risks Increase Over Time
If you smoke, the total number of cigarettes you smoke over time increases, raising your chance of developing cancer. “When I talk to a smoker and discuss the risks of lung cancer, I tell them, ‘You’ve been lucky so far, but as long as you smoke, your risk of getting cancer goes up every year,'” Davis says.
Lung cancer is not just a risk for smokers. Secondhand smoke — both from burning tobacco products and from inhaling the smoke a smoker exhales — is also a carcinogen. According to the Surgeon General, living with a smoker increases a non-smoker’s chance of developing lung cancer by 20 to 30 percent.
[See: 7 Innovations in Cancer Therapy.]
Quitting Really Does Make a Difference
If you quit smoking, your body begins healing immediately. According to the National Cancer Institute, smokers who quit before age 40 reduce their chance of dying prematurely from a smoking-related disease by about 90 percent.
Quitting makes a difference even if you’ve already been diagnosed with lung cancer. If you’re diagnosed with early stage cancer, your chance of complications is much higher if you’re still smoking, Gerber says. If you have late stage lung cancer, you may live longer if you quit smoking than if you don’t.
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How Smoking Causes Lung Cancer originally appeared on usnews.com
