[Evidence for cancer screening programs; what is a fitting metric?]

The introduction of cancer screening programs requires solid evidence of a proper balance between health benefits, harms and resources needed. The primary outcome measure in most randomized cancer screening trails so far has been cancer-related mortality. Collecting data on this outcome requires large study groups and adequate follow-up. Alternative primary outcome measures have been proposed, such as a stage shift, which has been selected in the ongoing UK NHS-Galleri trial. Recent commentaries have discussed the limitations of such alternative outcome measures in cancer screening trials.