Lung Cancer -- Is It Time To Start Screening?
Lung Cancer -- Is It Time To Start Screening?
Many smokers and former smokers worry about their risk of developing this disease. Here are some common questions and answers that reveal what most medical experts think about early detection of lung cancer.
Harvard Medical School
Lung Cancer — Is It Time To Start Screening?
Lung cancer is a common and devastating illness. Many smokers and former smokers worry about their risk of developing this disease. Presented here are some common questions and answers that reveal what most medical experts think about early detection of lung cancer.
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 220,000 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. Forty-four million people in the United States continue to smoke, and an equal number of ex-smokers remain at high risk of cancer and other deadly smoking-related diseases.
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 lung cancer with regular chest X-rays.
I have heard that CT scans might be better than chest X-rays at detecting early lung cancer.
Yes, CT scans of the lungs are better. 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. Until recently, early detection was not shown to improve lung cancer survival. However, the results of a large study called the National Lung Screening Trial were published in June 2011. The report suggests that screening heavy smokers with yearly low-dose CT scans can reduce deaths from lung cancer by 20% compared to screening with chest x-rays.
Should I start getting a yearly CT scan?
Smokers and ex-smokers who are age 55 or older and have a history of 30 pack years of smoking should consider a yearly lung CT scan. Pack years equals the number of packs smoked per day multiplied by the number of years a person has smoked.
What about radiation exposure?
Although the radiation dose is less than that in a typical CT scan, it is still many 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.
Are there other possible negatives about CT scans?
In the National Lung Screening Trial, about 24% of the CT scans showed areas of concern that required additional testing to determine if lung cancer were present. Yet 95% of these positive screens were "false positives." The abnormality turned out to be lymph nodes or inflamed tissue rather than lung cancer. While something that looks like cancer but isn't would be a result that any one would hope for, it took follow-up imaging, a biopsy of lung tissue, or bronchoscopy (in which a tube is threaded down into the airway) to make the final diagnosis. In addition to generating worry or even panic, these false positives sometimes led to injury during the follow-up procedures.
What else can I do to reduce my risk of lung cancer?
CT scans can't prevent lung cancer. At best, they might detect lung tumors early enough that they can be cured by surgery. The best way to prevent lung cancer is to never smoke or to quit. One of the lessons we've learned it that it is never too late to quit. If you quit at age 60, you stand to tack on about three years to your life expectancy. Quit at 50, and you earn six extra years. Quit at 30, and a whole decade is deposited into your life expectancy account. There's no better health deal around.
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