Lung Cancer Screening Gaining Momentum
A recent landmark study in the New England Journal of Medicine has doctors and policy makers optimistic about the potential to screen for lung cancer at an early stage. Using low- dose computerized tomography (CT) scanning of the chest in selected patients, researchers from the National Lung Cancer Screening Trial found that the total number of deaths from lung cancer could be reduced by an impressive 20%, and deaths from any cause could be reduced up to 7%. This represents a large improvement over previous research from the 1960s and 1970s, which many consider flawed and which used the less sensitive chest X-ray as the screening tool.
CT scans, like X-rays, use radiation to provide a detailed look at cross-sectional anatomy. CT is capable of detecting lung nodules as small as 1–2 mm, although most are not considered significant below 4 mm. Because CT scans can detect lung nodules—and potential cancers— in their earliest stages, this can lead to more effective treatment. As lung cancer is the leading cause of cancer death in the US and worldwide, an effective screening test would result in a significant decrease in the effects of this deadly disease.
The radiation exposure (effective dose) to a patient undergoing low-dose CT screening is around 1.5 milliSieverts (mSv), which is a very small amount. For reference, the average yearly background radiation an individual receives from natural sources is around 3 mSv.
A patient’s theoretical risk of developing a fatal cancer as a result of this low dose screening is around 0.008%.
is, positive results that do not actually represent cancer. In the large National Lung Cancer Screening Trial, in which 26,000 patients underwent screening CT for 3 years, only around 5% of the positive results turned out to be cancer. The follow-up of these false-positive results can lead to additional diagnostic testing, including invasive procedures such as biopsies or even surgery. Although the overall risk of these follow-up tests was proven to be low in the trial, it can add up to an expensive form of screening to the US healthcare system.
All patients and their doctors should be well- informed about the risks, benefits and implications of CT screening before undergoing the test.
Lung cancer screening is only recommended for high-risk patients. This is defined by the National Comprehensive Cancer Network (NCCN) as patients between the ages of 55–74 who have been smoking on average a pack per day for 30 years (30 pack years), OR who are older than 50, have smoked 20 pack years, and have one additional risk factor for lung cancer.
In summary, recent well-designed research studies have shown that low-dose CT scanning can save lives. The question remains as to how to best utilize the test and its results to provide the most benefit to patients at the lowest cost and lowest risk.