Early screening for lung cancer

A major risk that occurs in smokers and ex smokers is lung cancer. Are there steps that smokers or ex smokers can take to offset the effects of this terrible disease? The difficulty is that a disease like lung cancer can emerge in otherwise healthy people without early warning signs at all. Once it is diagnosed on the basis of symptoms the five-year survival rate is only 14% - it is a terrible prognosis and the leading cancer killer by a wide margin.

When a lung cancer is detected the tumour is ordinarily the size of a small orange and the cancer has usually already spread. An x-ray can reveal a cancer the size of a grape but a CAT scan can reveal a cancer tumour no bigger than a grain of rice. When such small cancers are detected the five-year survival rate jumps from 14 to 70%. Henschke et al. in an article in The Lancet in 1999 report on checks of 1000 smokers and ex smokers aged 60+ who showed no cancer symptoms using CAT scans and found 27 tumours of which 23 were early cancers. X-rays identified only 4 of these cancers.

This type of early diagnosis seems a possible way of significantly reducing mortality among those who have ever smoked. I would be interested in comments from those with a medical background - I don't have one - on this idea and particularly on the economics of such screening. Some useful websites I found are here and here. An excellent article with an extensive list of technical medical followup studies is here.

The literature is mixed with some sources claiming no beneficial effects and others stating that much can be achieved. Recent studies have suggested that 5-year survival rates of those identified using CAT scan procedures as suffering from early-identified cancers that are then surgically removed increases to 92% with the cost of a scan being between $200-$300US. There was one cancer victim detected for every 65 individuals tested in this sample of adults aged 40+ so the cost per cancer victim identified is over $16,000 although this could be reduced if the sample could be more effectively pre-screened by age and perhaps smoking history but even without this qualification the cost does not seem prohibitive.

The case for seeking to early screen for lung cancer is controversial. One claim is that there is over-diagnosis of cancers (many false positives) as a result of their procedures. In defence of the screening procedures however almost all of those identified as having small cancers who did not have them removed subsequently died within 5 years.

I have been trying to learn a bit about lung cancer. A useful guide to those suffering from this affliction – and those interested in dispelling myths - is C.I. Henschke, P. McCarthy and S. Wernick’s, Lung Cancer. It is full of interesting facts. It explains how lung cancers occur and how sufferers should seek treatment and perhaps how they should deal with the prospect of imminent death. It is a direct though very compassionate book.

I was interested in the argument that low tar cigarettes might be causing the adenocarcinomas in the smaller airways and alveoli in the lungs because people draw on these cigarettes more deeply.

To answer the question I posed initially – if you do smoke how should you act to reduce your risk of dying of lung cancer? The authors suggest that you make every attempt to quit smoking but otherwise take a low dose CAT scan annually.

What about ex smokers? The authors themselves only screen patients who are aged 40+ with at least a 10 pack-year smoking history. (Your pack-year history is the average number of packets you have smoked * number of years you have smoked). Quitting at any age increases your longevity – it is never too late to quit - but if you have ever smoked your risk of eventually suffering from lung cancer is permanently raised. About half of those suffering lung cancers in the US are ex smokers so the ideal response to the lung cancer issue is simple: If you don’t smoke don’t start and if you do smoke quit!

Update: The references Francis Xavier Holden provides in his comment, and the summary comments he makes, suggest it is too early to conclude that CAT scans are useful for the early detection of lung cancers. This seems a fair summary to me. The scans often identify slow-growing tumors not associated with cancer deaths. Faster growing malignancies are likely to occur between scans. Further research underway using very large scale surveys will report results in 2010. Interestingly, regular x-rays seem to increase lung cancer risks presumably through adverse effects of the x-rays themselves. Ex-smokers and current smokers in their 50s might not reduce their mortality by having regular CAT scans and regular, high-frequency x-rays may prove counterproductive.