• CT screening reduces lung cancer deaths

    January 2011

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    Two methods have been used to screen men and women at risk for lung cancer: low-dose helical – sometimes called spiral – computed tomography (CT) and chest X-rays. Researchers seeking to determine which screening method is most effective at reducing death from lung cancer found that heavy smokers screened with spiral CT had a 20 percent lower risk of dying from lung cancer than those screened with chest X-rays.


    Heavy smokers screened with spiral CT had a 20 percent lower risk of dying from lung cancer than those screened with chest X-rays.


    The findings are based on an interim analysis released in November 2010 of the landmark National Lung Screening Trial (NLST) comparing the effectiveness of the two screening methods at discovering early signs of lung cancer. According to the National Cancer Institute (NCI), in 2010 an estimated 222,520 people were diagnosed with – and 157,300 died of – cancer of the lung and bronchus.

    Use of chest X-rays

    Chest X-rays have long been used by doctors to diagnose lung cancer in people who have symptoms of the disease. But in 15 to 30 percent of the cases the disease has already spread beyond the lungs by the time lung cancer is diagnosed. Previous studies found no evidence that using chest X-rays to screen people without symptoms for early signs of lung cancer lowered mortality rates.

    CT can pick up much smaller tumors than can chest X-rays. The newer technology has been proposed as a screening tool to find early signs of lung cancer before it has spread in hopes of improving life expectancy. It is believed that the smaller the tumor when found, the higher the odds of long-term survival.

    NCI launches landmark study

    The randomized, controlled NLST was launched in 2002. It focused on 53,454 former and current heavy smokers ages 55 to 74 who had no symptoms of disease at the beginning of the study. Participants had smoked at least 30 pack years: those who smoked one pack a day for 30 years, two packs a day for 15 years, or three packs a day for at least 10 years. Former smokers were included if they were 30 pack-year smokers who had stopped smoking within the previous 15 years.

    Participants at 33 American sites were randomly assigned to undergo annual screening for three years with either CT scans or traditional chest X-rays. After the three rounds of screening, the participants were to be followed for five years.

    What the study found

    The study was discontinued earlier than planned because initial results showed that the group scanned with CT had a 20 percent lower risk of dying from lung cancer than those undergoing chest X-rays. There were a total of 354 deaths in the CT group, 442 in the chest X-ray group.

    Of those screened with CT, 24.2 percent had a positive finding for an abnormality compared to 6.9 percent of those screened with X-ray. However, 95 to 98 percent of those positive test results turned out to be false for those screened with CT; 93 to 96 percent turned out to be false positives for chest X-ray. This means that follow-up tests, such as invasive biopsies, found no signs of cancer in the majority of those participants whose CT or X-ray results indicated a possible abnormality.

    Because the study was discontinued early, results concerning the harm caused by the large numbers of false positives and the resulting follow-up tests and procedures have not yet been calculated. Also, data concerning the types of treatments provided to participants diagnosed with lung cancer, as well as details about the stages of cancer found, will not be available for several months.

    “Lung cancer is the leading cause of cancer mortality in the U.S. and throughout the world, so a validated approach that can reduce lung cancer mortality by even 20 percent has the potential to spare very significant numbers of people from the ravages of the disease,” said Harold Varmus, MD, NCI director. He cautioned that the results should not distract from efforts to curtail the use of tobacco, the main cause of lung cancer and other diseases.

    Study limitations

    The NLST only looked at heavy smokers, thus the results may not apply to those who have smoked fewer years and/or amounts of tobacco, who have a family history of lung cancer, or those who may be at risk due to second-hand exposure.

    Ninety-one percent of the participants completed the required three rounds of screening. The majority (59 percent) of the participants were men; most participants were between the ages of 55 and 59 (42.8 percent). The NLST noted that the study population ethnically represented the high-risk U.S. population of smokers; however, they were highly motivated and primarily an urban group screened at major medical centers. Thus, these findings may not accurately predict the effects of low-dose spiral CT screening for lung cancer in other populations.

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  • What the news means for you

    Scan's value outweighs risk

    Ronald McGarry, MD, PhD
    Radiation Medicine

    Wright, Heather, MDScreening for lung cancer has been attempted since the 1970s with no clear benefit – most likely because chest X-rays and other technology at the time were not sensitive enough to pick up signs of early disease. Based on the findings of the National Lung Screening Trial (NLST), we clearly see evidence that by using low-dose spiral CT scans to screen heavy smokers, more lives are saved than when using conventional chest X-rays.


    “The value of the scan far outweighs the tiny risk related to radiation doses in these patients at high risk for lung cancer.” 


    What makes this study impressive is that it has all of the needed ingredients for a disease screening study – no matter the disease. First, you need a population of people with a high incidence of the disease in order to make the screening cost effective or worthwhile. Clearly, this is the case with lung cancer, the No. 1 cancer killer. The National Cancer Institute (NCI) estimates there are more than 94 million current and former smokers in the U.S. at high risk for lung cancer. Cigarette smoking is the most important risk factor.

    Second, you need a screening tool that is effective and can detect the disease at a point where treatment can be successful. Using low-dose CT – higher doses of radiation are used for diagnostic CT when there are symptoms present – seems to be the obvious choice. Newer CT equipment gives very low doses of radiation.

    Concerns about CT scans

    Concern has been expressed in the media about radiation doses patients receive from CT scans. In this study, low-dose CT scans are used. The seriousness of lung cancer is such that the value of the scan far outweighs the tiny risk related to radiation doses in these patients at high risk for lung cancer. Most lung cancer is diagnosed at approximately age 60 and studies have shown that as we age, the health risks of exposure to diagnostic X-rays decreases.

    Treating lung cancer once diagnosed

    You need an effective treatment once follow-up tests document lung cancer. For stage I lung cancer, the stage where treatment is most effective, the current gold standard is radical surgery to remove the lobe of the lung where the cancer is located. Unfortunately, just removing the tumor – a lumpectomy for lung cancer – has not proven to be beneficial.

    For those who may not be surgical candidates, such as older patients or those who have other health problems, there is now a curative noninvasive treatment called stereotactic body radiation therapy (SBRT). This treatment has been shown to be effective in medically inoperable stage I non-small cell lung cancer – the most common form. Data recently presented at the annual meeting of the American Society for Radiation Oncology from a Japanese study shows that SBRT is also an effective treatment alternative for operable early-stage non-small lung cancer. This raises the possibility that radiation may be an alternative to surgery in some patients.

    UK is one of only 10 centers nationwide participating in several clinical trials of this emerging form of treatment. UK is also the only center in the country studying the use of SBRT on patients who have the most common stage of lung cancer — stage III (more advanced cancers).

    Who should be screened?

    Until the full findings of this study are released – which may take several months – we probably won't see specific guidelines concerning who should be screened with low-dose CT. This study was limited to healthy men and women ages 55 to 74 who were heavy smokers. Anyone concerned about a family history of lung cancer, a history of smoking or second-hand smoke exposure should talk to their doctor about whether a low-dose screening CT scan is advisable.


    “We should not lose sight of the fact that the most important thing anyone can do to prevent lung cancer is to never start smoking, or, if already smoking, quit.” 


    Effectiveness of screening

    Keep in mind that not all lung cancers found with screening will be early stage. Also, the vast majority of abnormal findings turn out not to be cancer. This means that many people may undergo invasive follow-up tests unnecessarily. And finally, most health insurance plans will not cover the cost of a screening CT scan used to look for initial signs of disease in healthy people.

    Keep in mind that not all lung cancers found with screening will be early stage. Also, the vast majority of abnormal findings turn out not to be cancer. This means that many people may undergo invasive follow-up tests unnecessarily. And finally, most health insurance plans will not cover the cost of a screening CT scan used to look for initial signs of disease in healthy people.

    While demonstrating that a screening low-dose CT scan can help save lives of lung cancer patients, we should not lose sight of the fact that the most important thing anyone can do to prevent lung cancer is to never start smoking, or, if already smoking, quit.

    Dr. McGarry is a radiation oncologist and a pioneer in use of stereotactic body radiation therapy (SBRT) for treatment of inoperable lung cancer. He is also clinical associate professor of medicine and vice chair of radiation medicine in the UK College of Medicine.

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