To help doctors give their patients the best possible care, the American College of Chest Physicians (ACCP) and the American Society of Clinical Oncology (ASCO) developed evidence-based recommendations on using computed tomography (CT) scans to screen for lung cancer in people who smoke or who have previously quit smoking. This guide for patients is based on the ACCP and ASCO recommendations.
- Lung cancer is more common in people who smoke, particularly those who smoke frequently or who have smoked for a long time.
- CT screening has been shown to lower the risk of death from lung cancer for heavy smokers, and the ACCP and ASCO recommend CT screening for certain people who smoke.
- Screening is not a replacement for quitting smoking. Quitting smoking is the only way to lower the risk of developing lung cancer.
More than 200,000 Americans are diagnosed with lung cancer each year. Most lung cancers occur in people who smoke or in those who have smoked in the past. Tobacco smoke damages cells in the lungs, causing the cells to grow abnormally. The risk of lung cancer from smoking is higher for people who smoke heavily and/or who have smoked for a long time. A common way to measure how much a person has smoked over his or her lifetime is in pack years. A pack year is the number of packs of cigarettes smoked per day multiplied by the number of years a person has smoked. For example, smoking one pack a day for 30 years or two packs a day for 15 years both equal 30 pack years.
Recently, results from the National Lung Screening Trial (NLST)  showed that there were 20% fewer lung cancer deaths in people who received screening with a low-dose CT scan than with a chest x-ray. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a patient's vein to provide better detail in the images.
Recommendations for Lung Cancer Screening
The ACCP and ASCO recommend the following lung cancer screening schedules for people who currently smoke or who have quit smoking:
- Yearly screening with a low-dose CT scan is recommended instead of screening with a chest x-ray or no screening for people age 55 to 74 who have smoked for 30 pack years or more or who have quit within the past 15 years.
- CT screening is not recommended for people who have smoked for less than 30 pack years, are younger than 55 or older than 74, have quit smoking more than 15 years ago, or have a serious condition that could affect cancer treatment or shorten a person's life.
What This Means for Patients
If you currently smoke, screening for lung cancer is not a substitute for quitting smoking. Quitting smoking is the only way to reduce your risk of lung cancer.
However, CT scanning may help find lung cancer earlier when treatment is likely to work better. The NLST showed that three lung cancer deaths were prevented for every 1,000 people who received CT screening. The benefit of screening also appeared to outweigh the risks of the radiation from the low-dose CT scans . There is a risk that CT screening can find abnormal areas in the lungs that are not cancerous. If an abnormal area is found on CT screening, more testing would still be needed to find out if it is cancerous or noncancerous. CT screening also increases the likelihood of being diagnosed with and treated for lung cancer because screening may sometimes find slow-growing cancers that would not have been found otherwise.
If you are considering lung cancer screening, it's important that it is done at a cancer center  that can provide the complete support and resources needed for the screening, as well as evaluating the images, managing the results, and diagnosing and treating cancer.
Questions to Ask the Doctor
Consider asking the following questions of your doctor:
- What is my risk of lung cancer?
- Can you help me calculate my pack years for my smoking history?
- If I still smoke, how can you help me quit?
- What are the risks and benefits of screening for lung cancer with a CT scan?
- Do you recommend I receive a CT scan to screen for lung cancer?
- Where can I receive screening that can provide assistance and support throughout the process?
- What are the next steps if the CT scan indicates cancer?
Find out more about this clinical practice guideline at www.asco.org/guidelines/lungscreening .
Quitting Smoking 
Guide to Lung Cancer 
Cancer Screening