Lung cancer is the leading cause of cancer deaths in women in the United States. In 2009, the American Cancer Society estimates that more than 70,000 women will die from lung cancer.

Cigarette smoking is the primary cause of lung cancer, and approximately 17% of women in the United States smoke. Between 1930 and 1997, the number of lung cancer deaths in women in the United States increased by 600%. Most of the deaths can be attributed to an increase in cigarette smoking by women. Over the last few years, the number of lung cancer deaths in women has stabilized, although it remains the top cause of cancer deaths in women.

Risk factors for women who don't smoke

Although smoking is the primary cause of the increase in lung cancer in women, lung cancer is diagnosed in women who have never smoked. Researchers think the following factors may contribute to the development of lung cancer in women who don't smoke:

• Genetic factors, such as how women's bodies react to carcinogens (substances that cause cancer)
  
  
• Environmental factors, such as exposure to secondhand smoke, radon, and asbestos.
  
  
• Hormones, such as estrogen

Doctors call lung cancer in women an epidemic, and they are looking for differences in lung cancer between men and women.

Women and smoking

From 1991 to 2005, the number of new lung cancer diagnoses in women in the United States increased by 0.5% per year, while the number of new lung cancer diagnoses in men decreased by 1.8% per year. The number of male smokers has declined by about half over the last four decades; however, the number of women smokers has decreased by only 25%.

Although the health risks of smoking cigarettes has been well publicized in the United States, many women still smoke. According to the U.S. Centers for Disease Control and Prevention (CDC), at least 500,000 teenage girls use tobacco products. Some of the reasons girls and women may be attracted to smoking include a belief that smoking can help control weight and advertising messages that target the needs and concerns of women. A 2005 study in the journal Tobacco Control analyzed the advertising messages from internal tobacco industry documents and public advertising collections. The study found that cigarette advertisements for younger women focused on the themes of friendship with other women, self-confidence, freedom, and independence. Advertising messages for older women included selling a woman's need for pleasure, relaxation, social acceptability, and an escape from daily life.

Once women become smokers, it is not known whether they are more likely than men to develop lung cancer from smoking. Some studies suggest that women have a higher risk of developing lung cancer, while some recent studies conclude that there is no difference. Cigarette smoking is addictive, and some evidence suggests that women may have more difficulty quitting smoking than men.

Lung cancer in women versus lung cancer in men

Lung cancer in women is a biologically different disease than lung cancer in men.

Women may have genetic and biologic differences that affect the development of lung cancer, which include the following:

• Genes that cause women to be more vulnerable to the harmful effects of tobacco smoke
  
  
• Differences in how the chemicals in tobacco are metabolized (broken down) by the body
  
  
• Changes to genes that control cell growth, which may result in the development of cancer
  
  
• A decreased ability of the body to repair damaged DNA, as DNA damage can promote the development of cancer
  
  
• Hormones, such as estrogen, which could directly or indirectly affect cancer growth

Treatment and survival differences

Women with lung cancer live longer than men, again for reasons that are not yet understood. For example, the five-year relative survival rate (the percentage of people who survive at least five years after the cancer is detected) is higher in women: 16% compared with 12% in men. Women with early-stage lung cancer who have surgery to remove the tumor live longer than men, as do women who are treated for lung cancer that has spread outside the lung. A 2007 study found that older women with early-stage lung cancer live longer regardless of the type of treatment they received.

Other studies have found that some types of treatment work better in women with lung cancer. For example, cisplatin (Platinol)-based treatment seems to be more effective in women. Doctors have reported that women (along with never-smokers; patients with adenocarcinoma (cancer in lung cells that secrete substances); and those treated in Japan, China, and Korea) were most likely to benefit from a drug called gefitinib (Iressa). Gefitinib is available only to people who were already taking it, had taken it in the past and had a good effect, or as part of a clinical trial (research study involving people). Clinical trials are underway to study whether similar drugs, such as erlotinib (Tarceva), are also more effective in women never-smokers or former smokers.

On the horizon

Researchers are just beginning to understand how lung cancer is different in women, and how this difference affects lung cancer treatment and survival. Additional clinical trials are needed to learn more about preventing, diagnosing, and treating women with lung cancer.

More Information

Guide to Lung Cancer

Tobacco

Quitting Smoking

Risk Factors and Prevention

Last Updated: November 12, 2009