There is an ongoing controversy as science and medicine advances, to the legitimacy of some forms of advanced cancer screening that can lead to false-positives. This debate has been stirred again by the National Lung Screening Trial that found while low-dose CT screening can reduce lung cancer mortality in heavy, long term smokers, it also has a false-positive rate of 20%.
False-positives in Cancer Screening
According to the results of a study published in the Annals of Family Medicine, The risk of a false-positive result from screening for prostate, lung, colorectal, and ovarian cancer is high and becomes cumulatively higher with ongoing screening. This trial reviewed results after 14 screenings in both men and women and found that the culmulative risk was 60.4% for men and 48.4% for women.
In many circumstances, this is an acceptable risk in light of the tremendous advantages of early detection. The concern is that in some cases, such as slow growing cancers like prostate cancer, the benefits offered do not outweigh the risks, because the patient is likely to die of other natural causes before the cancer ever presents symptoms. There is also some concern that mammography screening risks such as exposure to radiation, false-positives and overdiagnosis are not sufficient given the small number of deaths averted in women younger than 60.
The two primary issues surrounding false-positives are exposure to unnecessary invasive medical procedures and their inherent risks, and the extreme emotional toll that such a diagnosis leaves on an individual.
These factors have led to the U.S. Preventive Services Task Force and American Academy of Family Physicians recommending against prostate-specific antigen (PSA) testing to screen for prostate cancer. In regards to lung cancer screening with low-dose CT scanning, it recommends that it should be performed only on long term smokers in conjunction with smoking cessation interventions due to the high false-positive rate, uncertain harms from radiation exposure and risk of overdiagnosis.
Concern over Cost Effectiveness
With recent changes in health care, there is an increasing demand for fiscal responsibility in evaluating which health care procedures and practices produce a quantifiable result in relation to the amount of money spent to achieve that result. One tool used to evaluate this balance is a standardized measure of cost effectiveness called cost per quality-adjusted life-year (QALY). QALY calculates the amount of money that will need to be spent in order to produce an additional year of good health. It can also be used to calculate the fiscal value of treatments that produce a year less than optimal health.
Initial opponents of CT screening for lung cancer cited concern over the staggering amount of additional health care cost this procedure would incur. However, the National Lung Screening Trial showed the number of high risk patients that needed to be screened in order to save one life was 320, which compares favourably with mammography and colonoscopies. Further information from the National Lung Screening Trial is needed to determine the true cost effectiveness of lung screening, as current estimates vary widely from as low as $19,000 to about $169,000 per life-year saved.
The Centers for Medicare & Medicaid Services (CMS) Decision on Medicare
After looking at the trial and evaluating all risks and benefits, the Centers for Medicare & Medicaid Services (CMS) decided that a 20% reduction in death rate outweighed the potential risks of false positives or any concerns of cost effectiveness. They cautiously recommended lung cancer screening counseling and screening for lung cancer with low dose computed tomography (LDCT), once per year, as an additional preventive service benefit under the Medicare program, provided qualifying criteria were met.
This means that screening will only be covered if it is given along with a doctor’s advice of the benefits of non-smoking along with a doctor’s recommendation to patients between the ages of 55 and 74 years old, with no current symptoms of lung cancer, who have smoked a pack of cigarettes a day for over 30 years. Individuals who still smoke are included in coverage, as are those who have stopped smoking within the last 15 years.
Details of the National Lung Screening Trial
- The National Lung Screening Trial included 53,454 heavy smokers at high risk for lung cancer from 33 different U.S. medical centers, and was conducted from August 2004 to April 2004.
- Participants were between the ages of 55 and 74 years old, who had smoked one pack a day for 30 years or two packs a day for 15 years.
- The study included participants who had stopped smoking within the last 15 years.
- The purpose of the study was to evaluate the ability of low-dose CT screening to reduce the overall death rate in lung cancer patients, compared to the effectiveness of chest x-rays to do the same.
- Participants were randomly selected to receive either three annual screenings with low-dose CT scans, or chest x-rays. Data was then collected on cases of lung cancer and deaths from lung cancer that occurred through December 31, 2009.
- The participants who received low-dose CT screening for lung cancer had a 20% lower risk of dying of lung cancer when compared to those who had received chest x-rays.
What This Means for Heavy, Long Term Smokers
- Don’t stop trying to quit smoking.
If you haven’t been able to stop smoking, you’re not alone. According to the American Cancer Society, the overall success rate of smokers trying to stop smoking cold turkey, is around 4-7%.
But the success rates of those who use medications are significantly higher than those who do not. When you add medications that support the process, the rate is raised to around 25%. And those who added the services of therapy or a support group did even better.
If you have tried to quit unsuccessfully in the past, ask your doctor about aids to help you stop smoking.
- If you are at high risk, be proactive
If you are over the age of 55, and smoked a pack a day or more for 30 years or longer, don’t wait for your doctor to suggest it, ask about getting an annual low dose CT scan on your lungs. If he or she doesn’t wish to offer the service, find a physician who will. You will reduce your risk of dying by 20%.
- Know the Signs of Lung Cancer
Knowing the signs of Lung Cancer can save your life. You need to see a doctor when serious symptoms persist.
Symptoms in the chest:
- Severe, intense, persistent coughing. Or coughing that becomes significantly worse.
- Unexplained, persistent pain in the chest, shoulder, or back
- A change in color or volume of sputum
- Shortness of breath
- Changes in the voice, raspy voice
- Harsh sounds or wheezing with each breath
- Chronic lung problems, such as bronchitis or pneumonia
- Coughing up blood
Since many of these symptoms are everyday occurrences for the average smoker, it is easy to miss the signs of lung cancer. Iif your lung cancer has spread, you may have symptoms in other places in the body.
Symptoms of lung cancer elsewhere in the body:
- Loss of appetite or unexplained weight loss
- Muscle wasting
- Unexplained bone or joint pain
- Bone fractures not related to accidental injury
- Dizziness, memory loss, balance problems
- Neck or facial swelling
- Yellowing of skin or eyes
 - Croswell JM, Kramer BS, Kreimer AR, et al. Cumulative incidence of false-positive results in repeated, multimodal cancer screening. Annals of Family Medicine. 2009; 7: 212-222.
 - Kerlikowske K, Grady D, Barclay J, et al.: Positive predictive value of screening mammography by age and family history of breast cancer. JAMA 270 (20): 2444-50, 1993.
 - http://www.aafp.org/afp/2014/1101/p625.html
 - http://www.cms.gov/medicare-coverage-database/details/nca-proposed-decision-memo.aspx?NCAId=274
 - http://www.nejm.org/doi/full/10.1056/NEJMoa1102873