Screening for Lung Cancer with CT: Part I

The following is the first installment of a two-part discussion on screening for lung cancer with CT.

Until recently, the benefits of using computed tomography (CT) to screen for lung cancer were unknown. It was established that CT could detect cancers at an earlier and potentially more treatable stage; however, it was not clear that this made an overall difference in how long people survived. The National Lung Screening Trial (NLST) was designed to answer this question. A recently released preview of the data from the NLST showed that 20 percent fewer people died of lung cancer in the group screened with CT compared to those screened with chest x-ray. The overall difference in mortality (death) between the two groups was 7 percent.

What is the goal of a lung cancer screening CT?

The goal of any screening test is to prolong life. This is accomplished by detecting disease early, when it is potentially more treatable. For instance, some lung cancers found using CT screening are small and have not yet spread within the chest or to other areas of the body. Treatment is generally more effective at this stage. If screening is not performed, it is possible that a lung cancer would only be discovered after it has spread to other places in the body at which point it is much more difficult to treat.

Who should get a screening CT?

Unlike many other screening programs, lung cancer CT screening is targeted to a specific subset of patients. It is most useful for people who are at high risk for developing lung cancer, namely current or prior cigarette smokers. The length of time and number of cigarettes smoked affects whether a patient is a good candidate for CT screening. Most of the CT screening studies have been performed on patients who are 20-30 pack-year smokers. Pack-years are calculated by multiplying the average number of packs of cigarettes smoked each day times the total number of years smoked. If this number is ≥20 you may benefit from a lung cancer screening CT. Patients with a family member who has been diagnosed with lung cancer may also benefit from CT screening, particularly if that family member was a non-smoker.

Stay tuned for Part II, which will touch on some specific risks and benefits of screening with CT, including radiation issues.