Lung cancer was rare before the beginning of the 20th century, but it is now the most common cause of death from cancer among both men and women in the United States. An estimated 159,390 Americans died of lung cancer in 2009. Death rates are high because lung cancer is difficult to treat and usually is not detected until it has already spread.

Most lung cancer cases occur in people between the ages of 45 and 75 who have been exposed to cigarette smoke or other pollutants for many years. Tragically, only about 15 percent of people with lung cancer are alive five years after diagnosis.

Lung cancer may be primary or secondary. Primary lung cancer, which originates in the lungs, is grouped into two broad categories: small cell carcinoma (about 15 percent of cases) and non-small cell carcinoma (about 85 percent). Small cell carcinoma spreads especially quickly and is more difficult to treat; most people with this type die within a year of diagnosis. Primary lung cancer can spread to nearly any organ.

Cancer that has spread to the lungs from other sites in the body is called secondary lung cancer. These types of tumors are usually incurable, in which case palliative treatments are used. Palliative care is aimed at delaying progression of disease, relieving pain, and limiting disease complications, rather than curing the disease.

Q: I've just been diagnosed with early-stage lung cancer and my doctor wants me to quit smoking. What's the point?

A: A new study in the journal BMJ suggests that your doctor may be right. It finds that people diagnosed with early-stage lung cancer can double their chances of surviving five years if they stop smoking.

The investigators analyzed 10 studies that measured the effect of quitting smoking after a diagnosis of early-stage lung cancer. Using actuarial tables, they estimated that a 65-year-old with early-stage non-small cell lung cancer who quit smoking would have a five-year survival rate of 70 percent compared with 33 percent for a person who continued to smoke. For a 65-year-old with limited small cell lung cancer, the estimated five-year survival rates were 63 percent and 29 percent for a quitter and a continuing smoker, respectively.

A person with small cell lung cancer who continued to smoke was also more likely to experience a cancer recurrence and to develop a second primary cancer. In addition to worsening your lung cancer prognosis, smoking increases your risk of developing COPD, heart disease and other types of cancers. Your doctor can offer advice about how to begin a smoking-cessation program.

Publication Review By: Peter B. Terry, M.D., M.A.

Published: 14 Sep 2011

Last Modified: 27 Jan 2015