To Scan or Not To Scan for Early Lung Cancer
The National Cancer Institute funded this study that randomly allocated some 53,500 men and women at high risk (i.e., smoked about 1 pack or more cigarettes per day for 30 or more years) to either standard chest X-rays or low dose CT scans. Each person had a screening image taken annually for three years and were followed for an additional five years.
As of October, 2010, there were 649 cancers detected and 354 deaths in the CT group compared to 279 cancers and 442 lung cancer deaths in the X-ray group (obviously many of these latter cancer deaths were due to cancer NOT detected by the routine chest X-ray). The implication is that low dose CT scans detected cancer earlier resulting in successful therapy for many.
Lung cancer mortality per 100,000 was 246 and 308 for the CT group and the X-ray group respectively for a 20% reduction in lung cancer mortality.
But there are “buts” to the study. To save one life required 300 people to be screened. A CT scan costs at least $300 each, often much more. This means it cost $90,000 to save one life. Another “but” is CT screening detects lesions that are often not cancer. Indeed the false positive rate was about 25%. Since it requires a biopsy to prove it is benign, this adds not only risk and costs, but anxiety.
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The take away for now is that in high risk individuals, low dose CT scans can pick up early lung cancer. But the combination of high false positives and high costs weigh against its routine use even in these patients.