Lung Cancer Screening

Effective screening can identify lung cancer in its early stages, leading to improved treatment outcomes and survival rates. Commonly used screening options include chest X-rays (CXR), sputum cytology, and low-dose computed tomography (LDCT), all of which have been evaluated for their effectiveness in numerous randomized controlled trials (RCTs).

In the past, chest X-rays (CXR) and sputum tests were studied for lung cancer detection, but there wasn’t enough evidence to show they effectively reduced death rates from lung cancer.

However, Low-Dose Computed Tomography (LDCT) has been tested in two major studies: the National Lung Screening Trial (NLST) in the U.S. and the Nederlands-Leuvens Longkanker Screenings Onderzoek (NELSON) in the Netherlands. These studies showed that LDCT is effective in detecting lung cancer at an early stage.

Key Findings from the NLST

• Study Size: This trial, conducted in the early 2000s, involved more than 53,000 participants, including current smokers with a 30-year smoking history and former smokers who quit within the last 15 years.
• Design: Participants were divided into two groups: one received LDCT scans, while the other group had chest X-rays.
• Accuracy: The NLST demonstrated that LDCT can accurately identify lung cancer, with a sensitivity exceeding 90%.
• Mortality Reduction: After an average follow-up of 6.5 years, the LDCT group had a 20% lower death rate from lung cancer compared to the CXR group. A longer follow-up of 12.3 years confirmed these benefits.
• Early Detection: LDCT detected 46% more early-stage lung cancers compared to CXR and reduced the detection of late-stage cancers by 29%.

Key Findings from the NELSON Study

• Study Size: The NELSON study included nearly 16,000 current and former smokers aged 50 to 75 who had smoked >15 cigarettes per day for >25 years or >10 cigarettes per day for >30 years.
• Design: Participants were divided into two groups: one received LDCT scans, while the other had chest X-rays.
• Accuracy: After two years, LDCT had a sensitivity of 84.6% and a specificity of 98.6%.
• Mortality Reduction: After 10 years, LDCT screening led to a significant 24% reduction in lung cancer deaths among men and a 33% reduction among women (though the latter result wasn’t statistically significant).
• Early Detection: The LDCT group diagnosed significantly more stage I lung cancers (58.6%) and fewer stage IV cancers (9.4%) compared to those who did not get screened.

There is by far no local data to show the effectiveness of LDCT screening for individuals at high risk of lung cancer in Hong Kong. Moreover, there isn’t a validated tool to identify high-risk individuals or to establish specific guidelines for screening. Due to this lack of data, there is insufficient information to evaluate the benefits and risks of LDCT screening in our community, including which groups should be targeted and the best screening methods to use.

Based on studies from other countries, individuals with a significant smoking history (more than 20-30 pack-years) who are either current smokers or have quit within the last 10-15 years may benefit from LDCT screening. Most guidelines suggest starting screenings between the ages of 50-55 and stopping around 74-80 years old, with screenings typically done annually or every two years.

Since local guidelines haven't been fully established, individuals with a heavy smoking history should consult their doctors about the potential benefits and risks of LDCT screening. This includes understanding false-positive results and any follow-up tests that might be needed. It’s important to make an informed decision that is right for you. Please note that screening for lung cancer using CXR or sputum tests is not recommended.

Note: A pack-year is defined as smoking an average of one pack of cigarettes per day for one year. For instance, someone could accumulate a 20 pack-year history by smoking a pack a day for 20 years or two packs a day for 10 years.

The Centre for Health, Department of Health HKSAR

U.S. Centers for Disease Control and Prevention

Special thanks to Dr Wendy Wing-Lok Chan, Department of Clinical Oncology, the University of Hong Kong, for authoring this article.