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Tuesday, July 5, 2011

Screening CTs for Lung Cancer


Today’s Managing Health Care Cost Indicator is $674,000


Last week’s New England Journal of Medicine  reported a landmark study showing that screening low-dose CT scans really can save lives in people at high risk for lung cancer. 

The study is unequivocal – those who got screening CT scans were substantially less likely to die of lung cancer. Further, all-cause mortality was lower – even though a few people with CT scan screening died of exploratory surgery when they were found not to have cancer.

This study enrolled only smokers or ex-smokers with at least 30 pack years of smoking history, and excluded those who had signs or symptoms of cancer already, such as weight loss or coughing up blood.   It was peformed by the National Cancer Institute, and did not have funding from either companies that manufacture scanners or from tobacco companies.

The authors don’t recommend that all smokers and ex-smokers start getting annual CT scans.   Even with low dose scans, some cases of cancer are likely to result from massive screening – especially breast cancer in women. 

The level of “false positives,” abnormal CT scans that did not represent lung cancer, was stunningly high.  Over a quarter of study participants were found to have a scan suspicious for cancer in years one and two, and almost one in six in year three.  Only 1 in 20 abnormal CT scans suspicious of cancer actually showed a cancer. The control group received annual chest radiographs, and the CT scan group had a total of 119 excess cancers found – out of  18,146 suspiciously abnormal scans over the three year screening cycle.  That’s an increased case finding rate of 0.66% for the CT group compared to the radiography group.

Here’s the big public policy problem.   This study included 3 CT scans (at annual intervals) for just under 27,000 patients. At $1000 per scan, that would be a cost of over $80 million for the scans alone.  The cost of workup of all those false positives was substantially more.    The cost of just scans per incremental cancer found would have been $673, 664! ($80 million divided by 119) 

This study shows clearly why screening is unlikely to save dollars in the health care system.  The study took a group of high risk individuals – and even in this group, the false positive rate was quite high, and the cost per additional case found was very high.   

From a public policy perspective, we have to either
1)     Get scans that cost $100, rather than $1000.  We’ll need major disruptive innovation to allow that.
2)     Develop a more specific screening test, without losing sensitivity – so there won’t be 19 false positives for every true positive
3)     Develop less invasive followup tests to minimize the cost of pursuing the many abnormal tests

Of course, the best approach is to continue to levy high taxes on cigarettes, reinvigorate counter-marketing, and make cigarettes difficult for teenagers to obtain.  

Screening for lung cancer is not nearly as good as preventing lung cancer – and screening is far, far more expensive.

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