I have smoked a pack of cigarettes per day for 30 years and am worried about the risk of developing lung cancer.

You have good reason to be concerned. Approximately 215,000 Americans developed lung cancer last year, and the vast majority of these people smoked at some point in their life. Although other factors can contribute to lung cancer — including asbestos or other occupational and environmental exposures — smoking cigarettes is by far the most important. Fifty million people in the United States continue to smoke, and an equal number of ex-smokers remain at high risk of cancer.

Despite progress in many areas of medicine, the statistics for lung cancer remain grim. Death rates are about the same today as they were 30 years ago. More than 85 percent of those diagnosed with lung cancer will die of the disease. The total number of lung cancer deaths has gone down slightly in the past decade, mainly because of lower smoking rates for men. However, lung cancer still causes more deaths each year than do cancers of the breast, prostate and bowel combined.

Should I have regular chest X-rays to check for early evidence of lung cancer?

Most cancers start very small and grow slowly. If cancer can be detected at a very early stage — before it causes symptoms or spreads to other parts of the body — the chance for cure improves dramatically. In fact, screening for the early stages of disease is very effective for a number of cancers, including cancer of the breast (mammography), colon (colonoscopy) and cervix (Papanicolaou, or Pap, smears).

Lung cancer seems to be different, however. Several large studies conducted in the United States and elsewhere have looked at whether chest X-rays and sputum samples can detect lung cancer early. Although such screening increases the number of early stage cancers detected and improves overall survival, there has been no documented decline in lung cancer deaths.

Why these confusing results? The explanation is complicated and somewhat controversial. However, most experts agree that the apparent benefits of screening result from a statistical "sleight of hand." The fact that several studies failed to show a decline in the lung cancer death rate — what scientists consider to be the "gold standard" for screening tests — leads to the conclusion that chest X-rays and sputum samples are simply not effective in detecting lung cancer. To this day, most cancer experts and advisory panels recommend against screening for this disease.

I have heard that CT scans might be better than chest X-rays at detecting early lung cancer.

That is true, although the important word here is "might." Computed tomography, better known as a CT scan, is a technologically advanced type of X-ray that creates a three-dimensional picture of the lung. CT scans can find tiny growths that would be missed by most ordinary X-rays. The latest scanners are quick and use only modest doses of radiation.

Researchers have published impressive studies that show these scans can detect very small, early stage lung cancers. However, despite the high rate of early detection, no improvement in lung cancer survival has been demonstrated. In addition, some people have required surgery for what turned out to be benign spots. Because of the high cost of screening without any definite survival benefit, routine CT scans in smokers and ex-smokers is not recommended.

It seems common sense that chest X-rays and CT scans would be useful to screen for lung cancer. Why don't they work?

This is an excellent question, for which we don’t have complete answers. It is possible that lung cancer spreads so early that we cannot catch it soon enough. By the time we are able to detect most lung tumors — even with the best scanners — about 100 million cancer cells are present. Some studies suggest that microscopic spread has already occurred in most of these tumors and that survival statistics are no better with cancers that can be detected by CT compared with those detected by regular chest X-rays.

Even though chest CT scans have not been proven to reduce deaths from lung cancer, should I consider having one anyway?

Studies to examine the effectiveness of screening for lung cancer with CT scans are still ongoing. With the jury out, doctors remain divided on whether to offer CT scans to individuals who wish to be screened. If you are very worried about lung cancer and are willing to try an experimental screening test, I am certain that you can find a local hospital that offers this type of CT scan (often known as a low-dose, spiral or helical CT). Most insurance companies will not pay for this test, so be prepared to spend several hundred dollars out-of-pocket. Whether this is a worthwhile investment remains to be seen.

However, there are other reasons not to have this type of test. Although the radiation dose is less than that in a typical CT scan, it is still 10 times more than that in a chest X-ray. No one is sure of the long-term effect of getting this amount of radiation every year. Furthermore, for every cancer detected, there are about 10 individuals with an abnormal scan that requires follow-up. About 20% of people who get a scan have a suspicious spot that requires one or more follow-up scans. Although few biopsies or surgeries were performed for spots that turned out to be benign, the need to monitor these people required considerable time, money and radiation exposure, not to mention anxiety on the part of those individuals who were told that their scan was abnormal.

Are there other ways of detecting early lung cancer?

There are new technologies to look for the earliest evidence of cancerous cells. For example, a fluorescent dye that is absorbed by cancerous cells can be injected into the bloodstream. A special telescope is then inserted into the lungs to look for cancerous cells that "glow" because they contain the dye. Special dyes can also be used to examine lung cells that have been coughed up in sputum (phlegm). This is analogous to the Pap smear, in which cells from the cervix are examined under the microscope. However, this research remains very preliminary.

What else can I do to reduce my risk of lung cancer?

If you smoke, quit today. If you don't smoke, don't start. And if you develop any worrisome symptoms — a persistent cough, chest pains, blood in your phlegm or unexplained weight loss — make sure to see your health care provider.