Screening: More cons than pros?

St. Paul’s Hospital’s Department of Radiology recently began offering screening CT scans of the chest or whole body to the public on a private paying basis, using the CT scanner in off hours. As a result of this private enterprise, enough funds have been raised to allow more rapid performance of MSP-funded (i.e., medically necessary) scans. Thus, the current wait for a CT scan of the chest has decreased from 6 to 8 weeks to less than 1 week. “A successful combination of private and public funding,” many might say, but I find myself a little worried about getting a segment of the public used to the concept of screening tests when those tests have not been shown to be medically valid.

The principles of screening include choosing a high-risk population, providing a survival advantage to those with the disease, and making sure that the risks of investigating false positives are acceptably low.

The most common fatal malignancy in both men and women is bronchogenic carcinoma. Fifty percent of lung cancers are inoperable and therefore incurable at the time of presentation. This has stimulated many attempts over the years to find an effective way to screen for lung cancer, with the idea that early detection will lead to lives saved. All of these attempts have been singularly unsuccessful. A glimmer of hope has emerged with a new CT scan technique called low-dose helical scanning; preliminary results suggest that small cancers that were not visible on routine chest X-rays can be detected by this method. However, follow-up has not yet been sufficient to demonstrate a survival advantage, and in one study there was a significant number of false positives. And this was in a selected population of middle-aged smokers! How tragic it would be for all concerned to proceed to a thoracotomy to prove that a lesion is benign rather than malignant, only to have the patient die of a postoperative complication.

It behooves us all, if we are asked by our patients regarding these screening tests, to explain to them not only what the tests may discover of importance, but also what they may turn up that is better left unknown!

—LML