Annual lung scans recommended for some current and former smokers
Heavy smokers and former heavy smokers should get annual lung cancer screening tests, according to final guidelines issued recently by an influential U.S. panel. (1)
The final recommendations, issued by the U.S. Preventive Services Task Force, apply to people aged 55 to 80 whose smoking has put them at high risk of cancer. That includes former heavy smokers who have quit within the past 15 years. Heavy smokers are considered to be those who smoked a pack a day for 30 years, or two packs a day for 15 years.
The Task Force estimated that annual screening in this high risk population would reduce the risk of dying from lung cancer by 14%. Screening increases the chance of cure as it can detect lung cancer in the early stages when surgery is more effective.
Lung cancer is the leading cause of death from cancer in Australia in both men and women. Smoking causes 90% of lung cancer in men, 65% in women. However, most cases are found after the cancer has spread and only 12% of sufferers survive 5 years.
How is screening performed?
A low dose CT scan (previously called a CAT scan) is the recommended screening test. This procedure uses multiple x-rays and computer technology to create cross-section images of the lungs which can be examined in fine details. Other tests for lung cancer, such as chest XRays and sputum tests have not been found to be as reliable.
Modern CT machines use a much lower dose of radiation than in the past. A low dose CT lung scan delivers about 1mSv of radiation, compared to about 0.7mSv from a mammogram. Radiation from the multiple scans can increase lung cancer risk, but the effect is small (less than 1%) compared to smoking.
What are the other risks of screening?
One important risk of any type of screening is false positives, which occurs when a cancer is thought to be present on testing, but there is none actually found. This can lead to further unnecessary investigations and even surgery.
Another concern is that some cancers which are detected and treated may never have needed treatment if screening had not been performed.
What about smokers under 55 years?
The risk of lung cancer starts to rise after about 55 years so the benefit to younger smokers is much smaller. Also, screening from an earlier age results in a higher cumulative doses of radiation over a longer period which increases the risk of harm from testing.
Why do I need testing after I have quit?
The risk of lung cancer is still raised after quitting. The increased risk falls by 50% after 10 years and slowly declines further after that. (2) Annual testing is still recommended until 15 years after quitting. After that time, the risk is low enough that testing is no longer necessary.
Do I still need to quit smoking?
Annual scans will reduce the risk of dying from lung cancer by 14%. Although worthwhile, they will still not detect the great majority of lung cancer cases early enough for cure. The most important thing you can do to reduce your risk of lung cancer is to quit smoking as soon as possible.
2) Fry JS. How Rapidly Does the Excess Risk of Lung Cancer Decline Following Quitting Smoking. Regulatory Toxicology and Pharmacology 2013
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