Who gets lung cancer? You’re probably thinking the answer is people who smoke, and you’re not wrong. The most common types of lung cancer happen to people who smoke, and men and women are affected by these cancers in roughly equal numbers.

But did you know that a full 20 percent of lung cancer patients do not smoke and never did? More often than not, these lung cancer patients are young women.

“Women are disproportionately affected when it comes to non-smokers with lung cancer,” says Jeremy Cetnar, M.D., MSHPR, a medical oncologist at OHSU’s Knight Cancer Institute. “The typical non-smoker patient is young, female and of Asian descent.”

That’s because lung cancer in non-smokers isn’t caused by damage to the lungs. It’s caused by genetic mutations.

“There are four genetic mutations we know of that can cause lung cancer,” Dr. Cetnar says. “The most common ones, called EGRF and ALK, are most prevalent in women of Asian descent.”

The good news is that even though one in five lung cancer patients are non-smokers, this type of lung cancer is quite rare in the general population.

“We’re talking one in 100,000 or even 200,000 people,” says Dr. Cetnar. “It’s not something we even screen for because it’s so incredibly rare.”

For those who do have this type of lung cancer, diagnosis can be delayed. After all, when a young, healthy woman who doesn’t smoke has shortness of breath or a persistent cough, lung cancer is very unlikely to be the reason. So she may have symptoms for months before she has an x-ray or CT scan.

Fortunately, there are more and more targeted therapy options for these patients.

“For smokers with lung cancer, we use chemotherapy,” Dr. Cetnar says. “But for patients with mutations, we can use therapy targeted specifically to their mutation.”

This may mean fewer side effects and better treatment outcomes.