Screening is important for the high-risk non-smoker as there are other causative factors besides smoking that cause lung cancer
Lung cancer has long been associated almost exclusively with male smokers till recently.
Hence understandably screening for early detection of lung cancer has traditionally focused on people with a significant tobacco history. Whilst smoking remains the most common, most identifiable, and most preventable aetiological risk factor, alarmingly the proportion of non-smokers or never smokers developing lung cancer globally each year continues to rise.
The two widely cited published clinical trials (USA National Lung Screening Trial, 2011 & Dutch-Belgian NELSON 2020 study) that provide compelling evidence for the life-saving benefit of low dose computed tomography (LDCT) screening for lung cancer in high-risk individuals both target only heavy current or recent former smokers.
A recent landmark Taiwanese trial (TALENT) demonstrated the value of LDCT screening of the “high risk” non-smoker. The Taiwan national lung cancer screening study involving 12,011 individuals yielded a diagnostic pick-up rate of 2.6 per cent which was superior to the 1.1 per cent and 0.9 per cent lung cancer detection rates documented in NLST and NELSON respectively.
Notably, 73.8 per cent of the study population were women with an average age of 61.2 years, and 50.0 per cent had a family history of lung cancer. Fifty-three per cent of lung cancer deaths in Taiwan occur among never-smokers, suggesting other causative factors besides from smoking.
The high-risk non-smoker
Talent lead investigator Dr Yang Pan Chyr evaluated several high-risk features: a family history of lung cancer amongst first, second, or third-degree relatives; environmental smoking exposure; a history of chronic lung disease, such as tuberculosis or chronic obstructive pulmonary disease; cooking without ventilation; and a cooking index of 110 or greater (defined as 2/7 x the number of days of frying per week x the number of years cooking).
Lung Cancer Network Malaysia (LCNM) President Dr Anand Sachithanandan explains that lung cancer in the never-smoker is a rising global threat
and represents a disease distinct from the type of cancer which smokers develop in terms of genomic profile and tumour biology.
“It is also worth noting that 96.5 per cent of patients diagnosed in TALENT had early-stage disease amenable to curative resection or surgery,” adds Dr Anand who is also a Cardiothoracic Surgeon.
“We know that LDCT screening of heavy smokers can help catch lung cancer early and thus reduce mortality. This landmark study now paves the way for further exploration on the value of screening of the high-risk non-smoker especially those with a strong family history of lung cancer or a high cooking index.
“Till now there has been a paucity of evidence to support screening for the disease in non-smokers.”
Risk factors to consider
Chest Physician and LCNM Council Member Dr Hilmi Lockman noted the TALENT study identified family history as the most significant risk factor with a lung cancer prevalence of 3.2 per cent in patients with a family history of the disease compared to a prevalence of 2.0 per cent in those without.
He said risk was greatest when a first degree relative had the disease as opposed to more distant relations. Furthermore, the TALENT findings reiterate the importance of having a well-ventilated kitchen or the use of an extractor fan to mitigate the hazards of high temperate indoor wok cooking.
“LDCT lung cancer screening for the high risk never-smoker may be feasible but longer-term data is required to ascertain if LDCT screening in this population will lower the lung cancer mortality rates as has occurred with smokers.
“Nevertheless, this study will help redefine lung cancer screening criteria especially in Asia.” — The Health