Whither TNM?

Cancer staging has been the lynchpin of diagnosis, treatment, and prognosis for several years. However, new advances in molecular genetics, statistics, and computer science have been mounting a challenge to cancer staging in accurate prognostication. Staging systems, such as tumor-node-metastasis (TNM) classification, have been reacting to these challenges by increasing the number of stage groupings. In this article we examine the history of the number of increases in stage groups and argue that recent increases have not been accompanied by increased ease of use or better prognostic ability. We recommend that parsimony should be considered to counterbalance the instinct to increase the number of categories in future revisions of staging systems such as TNM.