Genes Play Role in Nonsmoker's Lung Cancer

Family members also at risk when a never-smoker gets the disease, study finds

TUESDAY, April 4, 2006 (HealthDay News) -- Parents, siblings and children of lung cancer patients who have never smoked face a 25 percent higher risk of developing one of a number of cancers, compared to close relatives of healthy nonsmokers.

These first-degree relatives are also more likely to be diagnosed with lung cancer, especially at an early age, strongly suggesting that genetics plays an important role in lung cancer among people who have never smoked.

"The genetics of susceptibility plays a role in never-smokers developing cancer," confirmed Olga Gorlova, lead author of the study and assistant professor of epidemiology at The University of Texas M.D. Anderson Cancer Center, Houston.

Gorlova presented the findings at a press conference held Tuesday in Washington, D.C., part of the annual meeting of the American Association for Cancer Research.

The study is one of the largest of its kind and the only one to include both men and women.

Lung cancer is the leading cause of cancer deaths, and tobacco is the single most important cause of lung cancer. People remain at risk for years after they stop using tobacco.

"Smoking remains the single most preventable cause of cancer," said Dr. Margaret Spitz, senior author of the study, professor and chair of the department of epidemiology at M.D. Anderson and moderator of the news conference.

Beyond that, some 10 percent to 16 percent of all lung cancer cases arise in people who have never smoked, Gorlova said.

To determine causes of lung cancer in patients who had never touched a cigarette, the research team compared cancer incidence between two groups of people: 2,465 first-degree relatives of 316 lung cancer patients who had never smoked and 2,442 first-degree relatives of 318 "controls" who had never smoked and did not have lung cancer.

Compared to the controls, first-degree relatives had a 25 percent increased risk of developing any kind of cancer, including melanoma, colorectal, head and neck cancer, lung, prostate and breast cancers.

Among the other findings:

  • Relatives of lung cancer patients were about 10 years younger than relatives of healthy controls when they were diagnosed with a tumor.
  • The average age of diagnosis with lung cancer was 60.6 years among relatives of never-smoker lung cancer patients versus 74.2 years for relatives of the healthy controls.
  • Family members of lung cancer patients had more than a six-fold increased risk of developing young-onset (before age 50) lung cancer than controls. Their risk of developing any type of cancer before age 50 was 44 percent higher.
  • Smoking relatives of lung cancer patients had a 68 percent higher risk of developing lung cancer compared to the controls.
  • Mothers of lung cancer patients had more than double the risk of developing breast cancer.

The next step is to try to identify the actual genes at play, Gorlova said.

"This is a very, very fine piece of work," said Dr. Jay Brooks, chairman of hematology/oncology at the Ochsner Clinic Foundation in Baton Rouge, La. "It shows that our genetics do make us susceptible to a number of diseases and we're beginning to define that genetic susceptibility even more."

"The important take-home piece is that it is extremely important to know your family history," he continued. "You can't take your genes away from you, but you can truly be very cognizant of the importance of controlling what you can control." In the case of lung cancer, for instance, society should continue to push for no-smoking bans to help limit the harm of secondhand smoke, Brooks said.

Other studies presented at the meeting looked at additional aspects of smoking and cancer.

One study, conducted by researchers at the National Cancer Institute, found that blood levels of a protein called CC10 were higher in people who had stopped smoking compared with people who were still smoking. The protein plays a role in protecting the lining of the respiratory tract and so may help explain why quitting smoking helps protect against lung cancer.

Another study found that women who are current or former smokers are at an increased risk of ovarian cancer, one of the first times such an association has been shown.

Finally, a third study found that lung cancer patients who have been exposed to secondhand smoke do not live as long as patients who have not been exposed.

More information

For more on lung cancer, head to the American Lung Association.

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