The National Lung Screening Trial (NLST) in Singapore falls short of identifying some individuals, particularly women, who are at an increased risk of developing lung cancer, according to a study. However, those who meet the criteria may derive significant benefits from the screening.
“The low smoking quantity of females in our cohort is a significant contributing factor for their exclusion from the screening criteria,” said the researchers, led by Chee Hong Loh from the Department of Respiratory and Critical Care Medicine, Changi General Hospital, Singapore. “Extending the upper limit of lung cancer screening age may also yield benefits for our ageing population.”
Loh and colleagues conducted a retrospective audit at Changi General Hospital from January 2018 to December 2018. They sought to describe the characteristics of patients with a lung cancer diagnosis and to reveal those who would be excluded from lung cancer screening when the NLST criteria was applied.
Only 38.1 percent of patients diagnosed with lung cancer met the NLST criteria strictly by age and smoking status. Those who met the criteria would have benefitted greatly from the NLST, given that 85.4 percent had presented at an advanced stage while 54.6 percent succumbed to the disease within 1 year. [Singapore Med J 2024;65:279-287]
“The majority of Singapore patients diagnosed with lung cancer, especially females, would not have been identified with the NLST criteria,” Loh said. “However, those who met the inclusion criteria would have benefited greatly from screening.”
When applying the United States Preventive Services Task Force criteria, the sensitivity of lung cancer diagnosis increased to 58.7 percent. Notably, only 15.5 percent of the female patients with lung cancer met the NLST criteria, and such exclusion was primarily driven by their low smoking quantity.
“Many females were not included in the screening criteria because of their relative lack of smoking quantity compared to males,” Loh said. “Local lung cancer screening criteria may need to be adapted to be inclusive of the female population due to their lower smoking quantity and the increased prevalence of female nonsmokers with adenocarcinoma in Asia.” [Singapore Med J 2019;60:554-559]
Previous studies
Another local study found that never smokers comprised 31 percent of the population diagnosed with lung cancer from 1999 to 2002, and this rose to 48 percent from 2008 to 2011. [Clin Lung Cancer 2018;19:e539-550]
In the present cohort, 33 percent were never smokers, while 40.5 percent (51/126) had a smoking history of <30 pack-years. Moreover, majority of the female patients (82 percent) were nonsmokers or smokers/former smokers with <30 pack-years compared to 74 percent of males with a significant smoking history (smoker or former smoker with >30 pack-years).
Regarding gender proportion, 73.8 percent of the present cohort were males as compared with 68.8 percent in the study by Toh and colleagues from 1999 to 2002 and 61.2 percent in the Lung Cancer Consortium Singapore cohort from 2008 to 2011. [Clin Lung Cancer 2018;19:e539-550; J Clin Oncol 2006;24:2245-2251]
“As we had more male smokers in our 2018 cohort and a smaller sample size, our data may overestimate the benefits of screening with the NLST criteria,” Loh said.
“Further research to derive the appropriate lung cancer screening criteria is paramount to maximize benefits and minimize risks for our local population,” according to the researchers.