Sebastian Schmidt: Lung cancer screening in smokers and non-smokers
Sebastian Schmidt, Head of Medical Affairs Computed Tomography at Siemens Healthineers, shared a post on LinkedIn:
“Lung cancer screening in smokers and non-smokers, recent publications (1 of 2)
I already wrote about risk (and overestimations) of overdiagnosis from lung cancer screening. Now the literature on this topic was extended by a recent publication in BMJ that deserves some comments.
They start showing data on deaths from lung cancer (1 in the chart below) and derive the conclusion, that the high lung cancer rates in non-smokers in Asia are largely due to overdiagnosis. Interestingly, the data in the upper chart is from the famous study on British doctors from 1956 (!), which is obviously not an Asian population. The lower chart is from a Japanese study from 2001, long before current guidelines were established.
To correct this misinterpretation, I took the numbers on mortality – death from lung cancer is, everyone will agree, for sure not overdiagnosis. IARC – International Agency for Research on Cancer / World Health Organization gives us very good statistics on the gender distribution of cancer deaths, and as women in China almost never smoke, the female mortality reflects non-smokers. You see that the age-standardized mortality in women is 15 and 40 in men, while only 2% of women smoke. So women die from lung cancer in China in large numbers, even without smoking. The same is true for most other East-Asian countries, simply look at the IARC databases.
Chart 3 shows the ratio men to women for three countries: Denmark, where smoking is equally distributed among genders, and so is mortality. Tunisia, where men smoke and have lung cancer, and women rarely – not East Asia. And China, where smoking is “male” and lung cancer also affects women.
Again: you find the same everywhere in the region.
The truth is: In addition to the well-studied (global) lung cancer (all countries), that often presents as squamous cell carcinoma and affect smokers, we have a second disease, lung cancer in non-smokers in East Asia.
It largely presents as Adenocarcinoma, grows more slowly, has a higher risk in women and a high incidence and death rate. While we very well know how to address the first kind of lung cancer through screening, we know less about the second kind. Very simply because most well-known studies were done in Western countries, while Asian studies were either smaller or are less known.
BMJ has been known for their skepticism on screening, which is okay – but I think they should check on scientific standards – deriving conclusions about Asia from a study on British doctors from 1956 is a bit “special”.
I will write about more misunderstandings in the article in a second post.”
Read The global cancer observatory of IARC/WHO.
Lung cancer screening in people who have never smoked: lessons from East Asia
Authors: H Gilbert Welch, et al.
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