Abstract
The prognosis of head and neck cancer is determined by numerous factors related to the patient, tumor, and health-care system. For many measures of outcomes, especially the key endpoints of organ preservation, locoregional control, occurrence of distant metastases, and survival, anatomic extent of disease remains one of the most powerful prognostic factors. This is embodied in the tumor–node–metastasis (TNM) classification, which historically has provided a very effective enabling tool to facilitate many elements of prognostication and cancer control. Traditionally, its contribution has been a codified classification and language to describe anatomic stage of disease for use in the clinic, determining eligibility and stratification for clinical trials and treatment protocols, and for comparison and surveillance of treatment results among centers and jurisdictions. More recently, momentum to include nonanatomic factors has grown, partly because it is recognized that anatomic extent of disease does not embrace all dimensions of prognosis. In particular, this relates to the quest to understand the biological dimensions of cancer, the deterministic effects of patient health, and the systems within which treatment is delivered that are needed to achieve more personalized and/or biologically driven therapies. Increasingly, there is a need in head and neck cancer to exploit new biological discoveries to permit modification of treatment and interventions in the clinic for this heterogeneous group of tumors. Because of this, the TNM staging has been criticized due to a perception that it has not been adapted sufficiently to modern needs despite its worldwide adoption. This may stem from the fact that there is no alternative uniform functional framework available to classify nonanatomic predictive and prognostic factors. The prevailing view is to regard TNM as the optimal receptacle for these factors due to its uniform appeal and success. As the field evolves, both anatomic disease extent and other factors, especially those addressing biological behavior of disease, need to be studied in their component domains as well as in combination using an agreed upon enabling taxonomy. An important strategy is to move toward constructing prognostic models to modify the current classification, which will not only include the TNM staging information but will also include other parameters of prognosis including comorbidities, lifestyle, and biochemical or genetic markers. In addition, experts in one area (e.g., translational science or clinical trial methodology perhaps) who may rely on TNM may not always consider that the classification provides very different needs for others (e.g., health services research or screening and cancer control initiatives, etc.) and vice versa. Ignoring or dismissing one dimension of prognosis compared to another will not be fruitful and the true contribution of each will remain unappreciated, and the goals of the prognostic factor effort in head and neck cancer may be left unfulfilled.