Screening for cancer with computed tomography

Advising patients is difficult given the lack of evidence

Whole body screening with computed tomography is the focus of a major advertising campaign in the United States. Enticing testimonials on billboards and radio spots urge the public to use this technology, implying that there is much to gain and little to lose. How should primary care doctors advise their patients?

In one sense screening with computed tomography has much to offer. As part of a study conducted by the National Institutes of Health, our centre has used computed tomography to screen for lung cancer for the past four years and has identified 56 lung cancers. Fully 62% of the non-small cell cancers were stage IA.1 In the absence of screening, only 15-20% of lung cancers present at stage IA. Five year survival for stage I lung cancers, which is about 60-70%, is higher than for cancers diagnosed at more advanced stages. There is little doubt that computed tomography is more sensitive than chest x ray in detecting small, early stage lung cancers. We found two cancers measuring only 3 mm in diameter.

Recognising that we found 56 patients with lung cancer, one could ask why …