Striving for an Enhanced Tumor Classification System: Reflections on Cancer, Prognosis, Human Nature and Reality

The TNM classification of anatomic tumor extent is a prominent part of the clinical care of patients with lung cancer. As treatment increasingly involves a blend of local and systemic therapies there is an increasing desire for an "enhanced TNM" that includes other factors that impact clinical decision-making. Typically, this is expressed as a need to include prognostic factors in the TNM classification to better predict patient outcomes. A clear understanding of the issues involved is needed in order to satisfy this desire in a way that is useful in clinical practice. We aim to add to the discussion of the topic in the lung cancer medical community by offering a perspective on what the TNM classification is, what the prognosis of patients as defined by tumor stage represents, and an exploration of what is meant when people talk about needing better prognostic prediction.