Lung cancer develops when cells in the lungs reproduce out of control. Over time, the cancer may spread to other parts of the body.

The biggest risk factor for lung cancer is smoking. However, lung cancer can also develop in people who have rarely or never smoked.

According to the Centers for Disease Control and Prevention (CDC), about 10–20% of lung cancers in the United States are among people who have never smoked or have smoked fewer than 100 cigarettes in their life.

People who smoke and people who don’t tend to develop different types of lung cancer. This may affect their treatment options.

There are two main types of cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). About 85% of all lung cancer cases are some type of NSCLC.

Adenocarcinoma is a type of NSCLC that develops in the lung’s air sacs. It accounts for an estimated 50–60% of lung cancer cases in people who don’t smoke, according to the CDC.

People who smoke are more likely to develop a type of NSCLC known as squamous cell carcinoma. This cancer accounts for about 10–20% of lung cancer cases in people who don’t smoke, according to the CDC.

SCLC makes up about 6–8% of lung cancer cases in people who don’t smoke. The remaining cases are other types of cancer, say the CDC.

Some people who don’t smoke may be more likely than others to develop lung cancer.

“It appears that lung cancer in nonsmokers is much more common in women, and particularly among those who are of Asian or Pacific Islander ethnicity,” Dr. Kevin M. Sullivan, an oncologist at Northwell Health Cancer Institute in Lake Success, NY, told Medical News Today.

Additional risk factors for lung cancer in people who don’t smoke include:

  • having a family history of lung cancer
  • having a history of certain lung conditions, such as pulmonary fibrosis
  • experiencing repeated or prolonged exposure to secondhand smoke, air pollution, and other cancer-causing agents, such as diesel exhaust, asbestos, radon gas, or heavy metals

Lung cancer in people who don’t smoke tends to be driven by a single genetic mutation in the tumor itself. People who do smoke are more likely to experience widespread genetic mutations that can lead to cancer.

Tumors in people who don’t smoke are more likely to test positive for changes in genes that make proteins involved in cell growth and division. These include:

  • EGFR gene mutations: Across two different studies, these mutations affected 37–45% of people with lung cancer who don’t smoke, compared with 7–14% of people with lung cancer who do smoke.
  • ALK gene mutations: In one study, these mutations affected about 12% of people who don’t smoke, compared with 2% of people who currently or used to smoke.
  • ROS1 gene mutations: These mutations occur in around 1–2% of people with NSCLC, according to the American Cancer Society. They are more common in people who don’t smoke than in people who do, according to a study in the Journal of Clinical Oncology.

People who smoke are more likely to have changes in the P53, KRAS, and BRAF genes.

A healthcare provider may prescribe a variety of treatments for lung cancer, based on:

  • the type, size, and location of the cancer
  • whether or not the cancer has spread to other parts of the body
  • the patient’s overall health, treatment history, and treatment preferences

A patient’s treatment plan for lung cancer may include one or more of the following:

  • surgery
  • chemotherapy
  • radiation therapy
  • immunotherapy
  • targeted therapy

“Lung cancer in never-smokers is an active area of research, and the treatment options for patients with lung cancer are rapidly changing,” said Dr. Sullivan. “I expect to see many more improvements in the care and outcomes for lung cancer patients in the future.”

Targeted therapies are one such newer treatment option. Healthcare providers prescribe these to people with lung cancer linked to certain genetic changes. Some common targeted therapies for people who don’t smoke include:

  • EGFR tyrosine kinase inhibitors: These are often used to treat lung cancer with EGFR mutations in people who don’t smoke. They have become a “mainstay of treatment” for such patients, said Dr. Sullivan.
  • ALK inhibitors: These can help treat lung cancer in people with ALK mutations. Some ALK inhibitors may also benefit people with lung cancer that tests positive for ROS1 changes.

Although lung cancer is much more common in people who have a history of smoking, it can also develop in people who have never smoked.

People who don’t smoke are more likely than people who do to develop a type of lung cancer known as adenocarcinoma. Lung cancers in people who don’t smoke are also more likely to test positive for changes in certain genes, including the EGFR, ALK, and ROS1 genes.

Multiple treatments target lung cancers that carry these gene mutations. As researchers continue to learn about these and other genetic changes, additional treatments may become available.