Increasingly higher quality research is strengthening the argument for screening high-risk individuals for lung cancer using computed tomography (CT). Many experts now agree that this screening may indeed give patients a better chance for a cure because tumors can be detected at an earlier stage.
The U.S. Preventive Services Task Force (USPSTF), an independent federal advisory panel of medical experts, advises screening with special low-dose CT scans for people ages 55 to 80 who either currently smoke or quit smoking in the past 15 years, with at least 30 “pack years” of smoking (an average of one pack a day for 30 years, for instance, or two packs a day for 15 years).
The USPSTF guidelines represent an update from its 2004 recommendations based on findings from several recent major lung-cancer-screening trials.
The most significant of these was the National Lung Screening Trial (NLST), in which screening with low-density helical (spiral) CT resulted in a 20 percent relative-risk reduction in lung cancer death.
The trial that made a difference
The NLST enrolled more than 53,400 men and women between ages 55 and 74. All were current or former heavy cigarette smokers, defined as a 30 pack-year habit.
Former smokers included only people who had quit smoking less than 15 years from the start of the study. All participants received either a chest X-ray or a CT lung scan every year for three years.
Researchers abruptly halted the 10-year study at the eight-year mark when they discovered that 20 percent fewer people in the CT group died of lung cancer than in the chest X-ray group. Continuing the trial without giving everyone the opportunity to receive CT lung scans would have been unethical, said researchers. The scans clearly saved lives in the study population.
Lung CT scans also seem to be as good as other cancer screening tests, if not better, at finding cancer. Researchers estimate that approximately 220 people would need a CT lung scan to prevent one lung cancer death. Contrast this with routine prostate-specific antigen (PSA) screening for prostate cancer, where about 1,400 men have to be screened to save one life, and breast cancer screening, where about 1,300 women ages 50 to 59 need a routine mammogram to save one life.
The USPSTF doesn’t recommend lung cancer screening using chest X-rays or sputum cytology—when mucus you cough up from your lungs is examined under a microscope—because they aren’t effective detectors of lung cancer.
CT scans are best at detecting non-small cell lung cancer, the most common type of lung cancer. The typical treatment for non-small cell lung cancer is surgical removal of the cancerous part of the lung.
Why is annual lung cancer screening essential?
More than 160,000 Americans die of lung cancer each year. The goal of screening is to detect cancer early enough so it can possibly be cured.
According to the USPSTF, 75 percent of lung cancer cases are diagnosed only after the disease has reached an advanced stage or spread to other parts of the body. The median five-year survival rate is 52 percent for people with lung cancer that hasn’t spread. The five-year survival rate ranges from 4 to 24 percent for people with cancer that’s spread. Compare those statistics with the survival rate among people whose lung cancer was caught at its earliest stage: 77 percent.
Increasing risk of age for lung cancer is one factor behind the USPSTF’s age range recommendation for screening 55- to 80-year-olds. The risk of lung cancer peaks at age 71, and two of three lung cancers are diagnosed after age 65. The benefits of screening smokers after age 80 are questionable, though.
Doctors need to take into account a patient’s overall health and ability to recover from treatment if cancer is found. Treatment can be hard on the body, and underlying illnesses can complicate recovery. This is true for people of any age. The USPSTF guidelines recommend discontinuing screening once a person has not smoked for 15 years or develops a health problem that substantially limits his or her life expectancy or the ability or willingness to undergo lung surgery.
If you’re at high risk and fall within the recommended age range but have other health problems, you may opt to skip screening because the potential risks of treatment may outweigh the potential benefit.
Low-dose lung CT screening has downsides. First, it exposes you to some radiation—less than that of a normal CT scan, but close to the same amount as that of mammography and more than that of a chest X-ray. The amount of radiation you’re exposed to depends on your body weight, the CT scanner type and manufacturer, and the area of lung scanned.
Lung CT screenings aren’t foolproof, either; they have a high rate of false-positives—that is, they frequently detect small lung nodules that are suggestive of cancer but aren’t cancerous. According to NLST results, 25 percent of scans showed abnormalities, but almost all turned out to be noncancerous.
This high rate exposes patients to unnecessary worry, repeated scans and radiation exposure, unnecessary lung biopsies, and even needless surgery—which happened in approximately 1 percent of false-positive cases in the NLST study. For example, a false-positive result may lead to an unnecessary biopsy, which can be painful and put you at risk for infection or a collapsed lung.
To lessen the risk of false-positives, CT scanning should be done in medical facilities with radiologists, oncologists, and surgeons who have expertise in interpreting scans and treating cancer.
Out-of-pocket costs for a CT scan may run between $300 and $500 (plus any additional charges from the facility where you undergo the scan). Currently, Medicare covers the cost of screening without a copay or deductible under the Affordable Health Care Act when specific conditions are met.
Put an end to the habit
The best way to avoid lung cancer is not to smoke, and if you do, quit. Even if you’ve been smoking over a long time, quitting now still decreases your lung cancer risk.
Other factors can contribute to lung cancer, such as exposure to secondhand smoke, radon, asbestos, and certain substances in the workplace, but smoking by far does the most damage to your lungs.
If you’re a past or present smoker who fits the criteria for lung cancer screening, talk with your doctor about whether you can benefit from a CT scan.