Projecting the yearly mortality reductions due to a cancer screening programme.

The decision on whether to implement a 20-year screening programme for a cancer requires weighing the harms and costs against the health benefits (such as the number of cancer deaths averted every year). The evidence of the benefits is often based on a single-number summary, such as the mortality reduction over the entire follow-up time in a single trial, or an average of such one-number measures from a meta-analysis of several trials. There are several problems associated with using the traditional one-number summaries from trials to deduce the yearly mortality reductions expected from a sustained screening programme. We here propose using a rate ratio curve, and its complement (a mortality reduction curve), to address the mortality impact (timing, magnitude, and duration) of a screening programme. This curve is easy to interpret, as it shows when mortality reductions begin, how big they are, and how long they last. We illustrate when and how such rate ratio curves from screening trials could be computed, and how they could be used to compare reduction patterns expected with different screening regimens. We encourage trialists to report the necessary data to arrive at such projections.