What is the number needed to treat (NNT) for low-dose computed tomography (LDCT) in lung cancer?

From the Guidelines

The number needed to treat (NNT) for low-dose computed tomography (LDCT) screening for lung cancer is approximately 320, as supported by the most recent and highest quality study 1. This means that about 320 high-risk individuals need to be screened with LDCT to prevent one lung cancer death over a period of about 6-7 years. The NNT is based on data from the National Lung Screening Trial (NLST) and other subsequent screening studies, which have consistently shown that LDCT screening reduces lung cancer-specific mortality and overall mortality in high-risk populations 1. LDCT screening is recommended for high-risk individuals, typically defined as adults aged 50-80 years with a 20 pack-year smoking history who currently smoke or have quit within the past 15 years. Some key points to consider when implementing LDCT screening include:

• The benefits of screening, including improved mortality outcomes and earlier detection of lung cancers at more treatable stages 1
• The potential harms of screening, including radiation exposure, false-positive results, and unnecessary invasive testing 1
• The importance of organized screening programs and multidisciplinary care teams to ensure safe and effective screening 1 The effectiveness of LDCT screening stems from its ability to detect lung cancers at earlier, more treatable stages, which improves survival outcomes. However, it's essential to note that the NNT may vary slightly depending on the specific risk profile of the population being screened and the duration of follow-up in different studies. Overall, the evidence supports the use of LDCT screening as an effective tool for reducing lung cancer mortality in high-risk populations, with a relatively low NNT compared to other cancer screening programs.

From the Research

Number Needed to Treat for Low-Dose CT in Lung Cancer

The number needed to treat (NNT) for low-dose computed tomography (LDCT) in lung cancer refers to the number of individuals who need to be screened with LDCT to prevent one death from lung cancer.

• The National Lung Screening Trial (NLST) found that with 3 rounds of annual LDCT screening, the NNT to prevent 1 lung cancer death was 323 over 6.5 years of follow-up 2.
• Another study, Nederlands-Leuvens Longkanker Screenings Onderzoek (NELSON), found that with 4 rounds of LDCT screening with increasing intervals, the NNT to prevent 1 lung cancer death was 130 over 10 years of follow-up 2.
• A study published in the New England Journal of Medicine in 2013 found that the number of lung-cancer deaths prevented per 10,000 person-years increased according to risk quintile, with the highest-risk group having the lowest NNT 3.
• The US Preventive Services Task Force (USPSTF) recommends annual screening for lung cancer with LDCT in adults aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years, based on a systematic review of the evidence 4.

Benefits and Harms of LDCT Screening

The benefits of LDCT screening for lung cancer include a reduction in lung cancer mortality, while the harms include false-positive results leading to unnecessary tests and invasive procedures, overdiagnosis, incidental findings, and increases in distress 2, 5, 6.

• The NLST found that for every 1000 persons screened, false-positive results led to 17 invasive procedures (number needed to harm, 59) and fewer than 1 person having a major complication 2.
• Overdiagnosis estimates varied greatly, ranging from 0% to 67% chance that a lung cancer was overdiagnosed 2.
• Incidental findings were common, with estimates varying widely from 4.4% to 40.7% of persons screened 2.