Imagine that there is no pseudodisease detected in current practice and that among 1000 patients diagnosed, only 100 are alive 10 years later (i.e. the 10-year survival is 100 divided by 1000 or 10%). Now imagine that in addition to identifying these cancers, spiral CT scanning also identifies 4000 patients with pseudodisease—all of whom survive 10 years, since they have non-progressive cancer. The new 10-year survival will include these patients in both the numerator and denominator—leading to a 10-year survival of 4100 divided by 5000 or 82%. Note that even though survival has changed dramatically, the number of people who die has not changed—under either condition 900 patients have died. This example demonstrates how survival rates can be increased by overdiagnosis, even if no one avoids death.