How is a computed tomography (CT) scan used for smokers?

From the Guidelines

A CT scan is recommended for current or former heavy smokers aged 55-80 with at least a 30 pack-year smoking history to screen for lung cancer. This low-dose CT scan of the chest can detect lung nodules and early-stage lung cancers before symptoms develop, when treatment is more likely to be successful 1. The screening is typically performed annually for eligible individuals who either currently smoke or have quit within the past 15 years. The procedure is quick, painless, and involves lying on a table that moves through a donut-shaped machine while X-rays create detailed cross-sectional images of the lungs.

The benefit of CT screening is significant - studies show it can reduce lung cancer mortality by 20-24% compared to chest X-rays 1. The radiation exposure from low-dose CT is minimal compared to the potential benefit of early cancer detection. If abnormalities are found, additional testing may be needed to determine if they are cancerous. This screening approach is particularly valuable because lung cancer often doesn't cause symptoms until it has spread, making early detection through screening crucial for improving survival rates.

Some key points to consider when recommending CT scans for smokers include:

• Age: 55-80 years old
• Smoking history: at least 30 pack-years
• Current or former smoker: yes
• Quitting history: quit within the past 15 years
• Screening frequency: annually
• Screening test: low-dose computed tomography (LDCT)

It's also important to note that smoking cessation is the most important intervention to prevent lung cancer, and advising smokers to stop smoking and preventing nonsmokers from being exposed to tobacco smoke are the most effective ways to decrease the morbidity and mortality associated with lung cancer 1.

From the Research

CT Scan Usage for Smokers

• A computed tomography (CT) scan is used for smokers to screen for lung cancer, with low-dose CT (LDCT) showing high potential for early detection 2.
• The CT scan can help identify lung cancer in its early stages, even before symptoms appear, and can reduce disease-specific mortality in smokers when stringent requirements and quality standards are met 2.
• Studies have shown that annual low-dose CT scans can reduce lung cancer mortality by 12% in smokers 2 and all-cause mortality by 7% 3.

Screening Guidelines and Effectiveness

• Current guidelines suggest that eligible adults with a heavy smoking history will benefit from annual low-dose computed tomography (LDCT) scans, but a shared decision-making consultation is required due to associated risks such as false-positives, radiation exposure, and overdiagnosis 4.
• The effectiveness of CT scans in reducing lung cancer mortality has been demonstrated in several studies, including the National Lung Screening Trial (NLST), which showed a 20% reduction in lung cancer mortality among heavy smokers 3.
• However, the risk of overdiagnosis and false positives is a concern, with estimates suggesting that between 19% and 69% of diagnosed lung cancers may be overdiagnosed 2.

Impact on Smoking Behavior

• CT scans may provide a "teachable moment" for smokers to quit, with one study showing that 14% of current smokers reported smoking abstinence at a 1-year follow-up after undergoing a low-dose CT scan 5.
• Older age and poorer lung function were associated with smoking abstinence, and a longer duration of smoking abstinence at baseline was predictive of abstinence in former smokers 5.

Implementation and Cost-Effectiveness

• Implementing a nationwide lung cancer screening program using LDCT scans would be expensive, with estimated costs of over $2 billion per annum 3.
• A possible low-cost strategy to risk-stratify smokers is to use spirometry measurements and emphysema scoring by radiologists on CT scans 3.