Lung cancer has been the most common cancer for several decades worldwide, both in terms of incidence and mortality. Based on the Ministry of Health Malaysia, it is the most common cancer among males and the third most common cancer in the general population in Malaysia. Incidence and mortality of lung cancer closely follow smoking trends with a time lag of twenty years.
If lung cancer is detected at an earlier stage when it is small and before it has spread, it is more likely to be treated successfully. There are a few ways to detect lung cancer, the best and recommended lung screening method for the high-risk groups is LDCT.
LDCT (Low-Dose computed tomography)
LDCT scans are able to find abnormal areas in the lungs that may be cancer. Studies show unlike chest x-rays, yearly LDCT scans can save the lives of people at higher risk of lung cancer. For these people, getting yearly LDCT scans before symptoms show up helps lower the risk of death due to lung cancer.
Who should screen for lung cancer?
The U.S. Preventives Services Task Force (USPSTF) recommends yearly lung screening using LDCT:-
(i) Adults aged 50 to 80 years; and
(ii) 20-pack-year smoking history; and
(iii) Currently smoking or have quit within the past 15 years.
A pack-year is smoking an average of one pack of cigarettes per day for one year. For instance, a person could have a 20-pack-year history by smoking one pack a day for 20 years or two packs a day for 10 years.
When should lung screening stop?
(i) A person who quit smoking for 15 years; OR
(ii) Has a health problem that substantially limits life expectancy or ability to have lung surgery if lung cancer is detected.
Risk of screening for lung cancer
(i) Over-diagnosis is when a disease may never have caused symptoms or become life-threatening resulting in unnecessary diagnostic procedures and unnecessary treatment.
(ii) False-positive test result is when results appear to be abnormal even though cancer is not present, which will lead to further tests (ie. biopsy) which imposes risks. Furthermore, it can cause anxiety.
(iii) Exposure to radiation from repeated LDCT may increase cancer risk.
Therefore, it is recommended only for adults who are at high risk of developing lung cancer to undergo lung cancer screening based on their smoking history and age, and who do not have a health problem that substantially limits their life expectancy or their ability or willingness to have lung surgery, if needed.
Other ways to detect lung cancer:-
- Chest X-Ray
However, chest X-rays cannot give a definitive diagnosis as they often cannot distinguish between cancer and other conditions, like lung abscess (collection of pus that forms in the lungs).
- Sputum cytology
Testing lung secretions or phlegm to look for cancerous cells. It is quick and inexpensive, however, it is only sometimes accurate. While the false-positive rate is as low as 1%, false negatives can occur, as high as 40% of tests. Due to its limitation, additional testing is required when the test comes back with a negative result when lung cancer is suspected. If results are positive for cancer, sputum cytology does not give sufficient information for doctors to be able to determine exactly what type of lung cancer a patient has.
It is essential to speak to your doctor about your risk of lung cancer, and the benefit and harm of getting a lung cancer screening. Then, decide whether you need one.
The best way to reduce your risk of lung cancer is to not smoke and avoid secondhand smoke. Lung cancer screening is not a substitute for quitting smoking.