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Sunday, March 11, 2007The studies looked at different populations, but they also approached the question of whether or not routine CT scans save lives in different ways. The pro-CT study lumped all of the patients with cancer together and estimated their 10-year survival rate as a group, regardless of cancer type. As you can see, a lot of people had to have biopsies (thousands) to detect a small number of cancers. The less-than-enthusiastic-about-CT scans study compared the number of cancers found by routine CT scanning, and their actual survival rates, with the number of cancers and their survival rates that one would expect based on past experience for their given populations. They also broke their cancers down into advanced and early. There were more cancers and more surgeries than predicted, but the number of deaths and the numbers of advanced cancers detected were what one would expect without screening. This is a particularly difficult point to communicate to patients. Most people believe intuitively that doing a periodic chest x-ray has the potential to save them from lung cancer. The worst scenario is when a patient is diagnosed with advanced lung cancer and then blames their physician for never doing a chest x-ray or CT scan, even if they didn't have any symptoms. In fact, you could have a chest x-ray every month and still die of advanced lung cancer. Lung cancer is one of those cancers that has many faces. There are some that are so aggressive, finding them early makes no difference. By the time they've shown up, they've already spread. There are others that are slow and passive and easily treated, even if we only find them once they become symptomatic. But try telling an angry cancer patient that. Especially one who read the first set of news stories touting the benefits of routine CT scans, but missed this weeks's news. posted by Sydney on 3/11/2007 03:09:00 PM 2 comments 2 Comments:
I'm a practicing radiologist in Texas, and the results of this study do not surprise me in the least. IIRC, the original study for low-dose CT screening came out of NYC, and when it was repeated at Mayo the results were not so rosy. The midwest is the histoplasmosis belt, nearly everyone here has one or more tiny masses in their lungs, some calcfiied and some not. The calcified ones we know what they are, the non-calcified are overwhelmingly non-calcified and benign granulomas, but only a couple years of observation will establish that. The SPNs that stand out so well in NYC are masked by many more pulmonary masses in the remainder of the lung fields in the midwest and south.
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Ovarian cancer is the same way. By the time it is detected by "screening" methods, it's too late. It's a disease that does not lend itself to screening because there is no precancerous stage, no preclinical stage during which it can be reliably detected, and all tests have a high false-positive rate and/or high cost.
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