Lung cancer screening in Hong Kong: what the expert working group recommends, low-dose CT scans, and what heavy smokers should discuss with a doctor

What does Hong Kong recommend on lung cancer screening?

The Cancer Expert Working Group on Cancer Prevention and Screening (a Government group; ‘the Working Group’ below) revised its recommendations on lung cancer prevention and screening, which were endorsed by the Cancer Coordinating Committee on 12 June 2023 and serve as a general reference for doctors giving individual advice to people in Hong Kong; the recommendations apply only to people without symptoms.

Smoking is the most important risk factor for lung cancer, lung cancer screening cannot replace quitting smoking, and quitting, or never starting to smoke, remains the best way to prevent lung cancer (Working Group, June 2023). For quit-smoking services in Hong Kong, see Quit smoking services in Hong Kong. Individual cases are decided by the treating doctor.

What are the benefits and risks of low-dose CT scan screening?

The National Lung Screening Trial (NLST) in the United States and the Dutch–Belgian NELSON trial showed that low-dose CT scans can detect lung cancer at an earlier stage and reduce lung cancer deaths among high-risk people; in the NLST, compared with the group that had a chest X-ray every year, the group that had low-dose CT scans had a relative reduction in lung cancer deaths of 20% (median follow-up 6.5 years), and participants were current smokers aged 55 to 74 with a smoking history of 30 pack-years, or people who had quit for no more than 15 years (Working Group, June 2023).

The harms include false-positive results, overdiagnosis (finding lung cancers that would never have become clinically significant in the person's lifetime), radiation, and short-term psychological distress; a false positive may lead to unnecessary follow-up tests and even invasive procedures such as biopsy and bronchoscopy, which are uncommon but carry a risk of serious complications and even death (Working Group, June 2023). In the NLST, the average false-positive rate per screening round was 23.3% (Working Group, June 2023).

Health care professionals should explain to people undergoing low-dose CT scan screening the benefits, the potential harms, and what the possible results mean and the distress they may cause (Working Group, June 2023).

When the recommendations were published, there were still no studies assessing the effectiveness, cost-effectiveness and benefit–harm balance of low-dose CT scans for high-risk people in Hong Kong, and no locally validated risk assessment tool to define high-risk people; local data are insufficient to recommend a population-based low-dose CT scan lung cancer screening programme for people at increased risk (Working Group lung cancer recommendations, June 2023).

The Working Group states that it will periodically review the latest evidence on low-dose CT scan lung cancer screening and update its recommendations as appropriate (June 2023).

What counts as heavy smoking? How are pack-years calculated?

A pack-year is the number of packs of cigarettes smoked per day multiplied by the number of years smoked (Working Group, June 2023).

Drawing on overseas literature, the Working Group regards people with a smoking history of more than 20 to 30 pack-years who either currently smoke or have quit for not more than 10 to 15 years as people at increased risk who may benefit from low-dose CT scan screening; most overseas recommendations start screening at 50 to 55 years and stop at 74 to 80 years, usually screening every year or every two years (Working Group, June 2023). Whether these overseas criteria apply locally remains to be investigated (Working Group, June 2023).

Adults in the United States aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years are recommended by the US Preventive Services Task Force (USPSTF) to be screened with a low-dose CT scan every year (March 2021). This is a US recommendation, not a Hong Kong one; individual cases are decided by the treating doctor.

If I already have symptoms such as a cough, is it still screening?

The Working Group's screening recommendations apply only to people without symptoms (June 2023). Possible signs include a persistent cough, wheezing, blood in the sputum, chest pain, prolonged fatigue, loss of appetite and weight loss; people with these symptoms should see a doctor as soon as possible (Cancer Online Resource Hub lung cancer page, April 2026).

Most symptoms of lung cancer can be caused by other conditions, but people should seek medical attention as soon as possible when they first notice any symptom or change, because delayed diagnosis may lead to poorer treatment outcomes (Working Group, June 2023).

Want to know the process after diagnosis, or how to choose a doctor?

For the process after diagnosis, see Lung cancer: what are the usual steps from diagnosis to starting treatment?; for choosing a doctor, see How to choose a lung cancer doctor and How to choose a respiratory physician; for private hospital charges for CT scans, see CT scan fees; for the English name of lung cancer, see Lung cancer in English. Individual cases are decided by the treating doctor.

Frequently asked questions