The "Will Rogers effect" on stage grading.

Will Rogers phenomenon affects survival statistics applied to clinical research and could determine a misreading of results. Stage migration due to new methods of diagnostic imaging and staging invasive procedures could improve actuarial survival in each stage. TNM System is impaired when survival rates come from different inhomogeneous countries, regions and eras. Randomized trials suffer this fallacious phenomenon when staging depends on the different treatments which are to be evaluated.