Study: More Than 12% of People Newly Diagnosed with Lung Cancer Never Smoked Cigarettes

Smoking cigarettes is the biggest risk factor for lung cancer and causes about 80% of deaths from the disease. But people who don’t smoke can develop lung cancer too. A new study found that out of 100 people in the United States who were recently diagnosed with lung cancer, about 12 of them (12%) had never smoked cigarettes. The study was co-led by the US Centers for Disease Control and Prevention (CDC) and the American Cancer Society (ACS). The results were published in a research letter in JAMA Oncology.

While other studies have shown increases in the number of lung cancer patients who had never smoked cigarettes in both the US and United Kingdom (UK), this study offers greater insight into the rate at which people are diagnosed with lung cancer. Instead of pulling data from local hospitals as smaller studies have done, this study used a large sample of over 129,000 cases of lung cancer based on data from cancer registries in 7 states.

The data was collected from 2011, when the CDC National Program of Cancer Registries began obtaining cigarette smoking history from patient medical records, to 2016.

New insight into “never smokers” and “ever smokers”

The study offers a more detailed look at recently diagnosed lung cancer patients based on their smoking history.

In “never smokers” (people with a recent diagnosis of lung cancer who never smoked), the researchers found a higher percentage of:

• Women (about 16%) across all age groups, races/ethnicities, and most types of lung cancer  in comparison to men (about 10%).
  
• People ages 20 to 49, including women (about 28%) and men (about 19%).
• People with the adenocarcinoma type of non-small cell lung cancer, compared with other types of lung cancer. This was consistent with previous studies.

In “ever smokers” (people with a recent diagnosis of lung cancer who currently smoke or used to smoke), the researchers found a higher percentage of:

• Men (90%) than women (84%). About half of men and women ages 20 to 64 were current smokers.
  
• Current smokers who are Black compared to whites or Hispanics. 

More research on lung cancer in never smokers needed

People who have never smoked who develop lung cancer are more likely to be women and younger. Adenocarcinoma is the most common type of lung cancer seen in this group. Risk factors for lung cancer not related to smoking include exposure to secondhand smoke, radon, air pollution, and chemicals and materials at work such as asbestos.

Future cancer research focused on people who have never smoked may help researchers improve their understanding about the effect of genetic and other risk factors besides smoking on lung cancer. 

Smoking still causes most lung cancers

The large percentage of ever smokers who were recently diagnosed reinforces “the need to strengthen and increase smoking cessation,” according to ACS researchers Stacey Fedewa, PhD, and Ahmedin Jemal, DVM, PhD, who were co-authors of the study. Previous ACS research has shown that this can be done with state and federal tobacco control policies that promote smoking cessation and with more doctors advising their patients to quit.

A person’s risk is affected by the number of packs of cigarettes they smoke a day and the number of years they smoke them. People who actively smoke or used to smoke should talk to their doctor about their risk of lung cancer and getting screened with a low-dose CT (LDCT) scan.