Lung cancer used to be known as a disease of old men, but an interesting shift in its pathology is occurring and medical experts throughout the world are in the process of trying to learn why.
For years, researchers have watched lung cancer rates drop in the U.S., except in one group – adults younger than 40 with no history of smoking.
Members of this demographic often are diagnosed with aggressive cases of non-small-cell lung cancer, the same as many longtime smokers.
Today, up to 20 percent of new lung cancer cases in men and more than half of new cases in women occur in nonsmokers.
Dr. William McGarry, a board-certified hematologist and medical oncologist at Florida Cancer Specialists & Research Institute, says “there are a lot of theories as to why there is this increase in younger nonsmokers,” at time when overall lung cancer rates are dropping worldwide.
Genetics is one thing that may play a role, he says.
According to the American Lung Association, some people inherit DNA mutations from their parents that greatly increase their risk for developing certain cancers, and genes seem to play a role in some families with a history of lung cancer. For example, people who inherit certain DNA changes in a particular chromosome (chromosome 6) are more likely to develop lung cancer, even if they don’t smoke or only smoke a little.
Other people seem to inherit a reduced ability to break down or get rid of certain types of cancer-causing chemicals in the body, such as those found in tobacco smoke.
However, most gene changes related to lung cancer are usually acquired during a person’s lifetime rather than inherited. They often result from exposure to environmental factors such as cancer-causing chemicals in tobacco smoke. But some gene changes may just be random events that sometimes happen inside a cell, without having an outside cause.
Dr. McGarry says the role that the EGFR mutation plays in nonsmokers who develop lung cancer is being carefully studied.
EGFR stands for Epidermal Growth Factor Receptor. It is a protein most often found in skin cells, although it can be found elsewhere in the body. An EGFR mutation can negatively affect how the EGFR protein functions.
The Lung Cancer Foundation of America explains that the job of EGFR is to help cells grow and divide. In the case of EGFR-positive non-small-cell lung cancer, a mutation, or damage, in a gene causes the epidermal growth factor receptor to remain stuck in the “on” position. This “drives” abnormal cell growth and cancer.
The EGFR biomarker is important in many cancers, including lung cancer. It was the first biomarker identified as a potential “target” for personalized treatments in lung cancer.
EGFR-positive lung cancer is more common in certain populations, including:
- People who have never smoked or only smoked a little
- People with lung adenocarcinoma
- Women
- Young adults with lung cancer (EGFR mutations are present in roughly 50 percent of lung cancers in young adults)
- People of Asian or East Asian heritage
Biomarker testing can determine if a patient has EGFR-positive lung cancer.
“For women, the role of exposure to hormones as a cause of lung cancer is a controversial one,” says Dr. McGarry.
Indeed, many scientists believe estrogen may play a role in the risk of lung cancer in women, although the evidence is conflicting. It’s not clear if the hormone promotes or hinders lung cancer, according to a review of studies published in the journal Cancers in June, 2023.
Some studies suggest that estrogen promotes lung cancer growth in clinical practice and in experimental models, but there are also several studies that indicate estrogen’s protective benefit against lung cancer in women who have not had their ovaries removed, per the review.
Because of these theories, some researchers believe that reproductive factors, which involve the presence or absence of estrogen, may impact the risk of a woman eventually developing lung cancer.
Everyday Health, which produces online newsletters that deliver content on health information and medical research, reports that researchers have discovered that several reproductive factors showed a significant association with a higher risk of lung cancer among women, including the following:
- Early menstruation, at age 11 or younger.
- Women who went through menopause between 45-50 years of age.
- Women whose reproductive span (the time between starting your period and menopause) was 32 or fewer years.
- Women who were between 15-20 when they first gave birth.
The American Cancer Society advises that lung cancer in people who don’t smoke can be caused by exposure to radon, secondhand smoke, air pollution, or other factors that cause gene mutation. Workplace exposures to asbestos, diesel exhaust, or other carcinogenic chemicals can also cause lung cancers in some people who don’t smoke.
Nonsmokers are not routinely screened for lung cancer and, according to data from Mayo Clinic, the disease usually doesn’t cause any symptoms when it’s in an early stage. As the cancer progresses, signs to look for include:
- A new and lingering cough
- Coughing up any amount of blood
- Feeling short of breath
- Pain in the chest
- A hoarse voice
- Unintentional weight loss
- Bone pain
- Headaches
Yale University School of Medicine offers an optimistic assessment to nonsmokers who develop lung cancer. “We used to think all lung cancers were the same, but now we understand that there are different kinds,” says Anne Chiang, MD, Ph.D., a Yale Medicine thoracic medical oncologist, and deputy chief medical officer for the Smilow Cancer Hospital and its Care Centers. “The good news is that the types of lung cancer that nonsmokers tend to get are usually driven by a molecular change or mutation that can be detected in the tumor, and there are drugs and therapeutics available to effectively treat them.”
Dr. William McGarry attended the University of Florida College of Medicine. He completed his residency at University of Florida Shands Hospital. He completed fellowships in medical oncology at the University of Texas M.D. Anderson Cancer Center, and medical hematology at University of Texas. Dr. McGarry is board-certified in medical oncology, hematology and internal medicine. He sees patients at Florida Cancer Specialists & Research Institute locations at 3730 7th Terrace in Vero Beach: 772-567-2332; and at 13060 U.S. 1 in Sebastian: 772-589-0879.
