Study: CT screening would cut lung cancer deaths in China

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Using a statistical model, Chinese researchers found that CT screening could reduce deaths from lung cancer in China by 24% compared with no screening, mostly by reducing deaths among smokers, according to a paper published July 14 in the Chinese Journal of Cancer.

Lung cancer has become a major problem in China: A 2016 report by Chen et al found that there were 733,000 new cases and 610,000 deaths from lung cancer in China in 2015. High smoking rates and high levels of exposure to carcinogens such as air pollution are believed to be driving the rates.

While low-dose CT screening has been investigated as a tool for reducing lung cancer mortality in Western countries, little research has been done in China, wrote the team led by Zixing Wang and Wei Han of the Institute of Basic Medical Sciences at the Chinese Academy of Medical Sciences in Beijing. In particular, public policy advocates would need to know the effect of different screening strategies on mortality before rolling out a population-based program (Chin J Cancer, July 14, 2017).

It can take years to perform a randomized controlled trial like the National Lung Screening Trial (NLST) in the U.S., which demonstrated that CT lung screening reduced mortality by 20% compared with x-ray screening. So the researchers decided to use a statistical model to estimate the effect of different screening strategies on mortality in China, comparing CT with both x-ray screening and no screening at all.

They generated a simulated cohort of 100,000 urban Chinese smokers ages 45 to 80, of whom 94,012 were men and 5,988 were women. Lung cancer prevalence was estimated using data from national registries and epidemiological surveys. The screening protocol consisted of one round of screening for smokers with no annual follow-up studies; the researchers used "relatively relaxed" criteria to define a smoker, regardless of factors such as daily smoking amount or number of pack-years.

The researchers determined there would be a total of 721 lung cancers in men and 46 in women in their simulated cohort. They found that CT screening would produce the greatest reduction in deaths from lung cancer, but at the price of more false diagnoses and deaths from follow-up procedures.

Effect of CT lung screening in China for smokers ages 45-80
  No screening X-ray screening CT screening
No. of lung cancer deaths 591 541 448
Reduction in deaths compared with no screening N/A 50 143
Percent reduction in deaths compared with no screening N/A 8.5% 24.2%
No. of false diagnoses N/A 2,497 9,387
Deaths due to false diagnoses N/A 2 7

Given the high number of false diagnoses, Wang, Han, and colleagues recommended that screening programs be tailored to produce the maximum benefit versus harms. For example, individuals older than 75 may not tolerate follow-up studies as well as younger people.

They recommended an age range of 55 to 75 as being optimal; screening would reduce lung cancer mortality by 24.5% in this group, compared with no screening. This focus would cover 64% of those ages 45 to 80 who are most likely to have lung cancer.

Further, CT lung screening should be targeted to areas of China with the highest smoking rates, as a secondary finding of the study was that the effectiveness of screening in reducing death rates paralleled the proportion of smokers in the hypothetical cohort.

The study results suggest that population-based CT screening would reduce lung cancer mortality in China, the researchers concluded.

"Our findings indicate that screening old smokers in urban China with low-dose CT would reduce lung cancer deaths," they wrote.

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