Inclusion of comorbidity in a staging system for head and neck cancer.

The widespread use of the TNM staging system has helped standardize the classification of cancers. Despite its excellence in describing a tumor's size and extent of anatomic spread, the TNM system does not account for the clinical biology of the cancer. Clinical factors, such as symptom severity, performance status, and comorbidity, which are important for classification, prognostication, and evaluation of treatment effectiveness, remain excluded from this system. In several studies of cancer prognosis, the presence of severe comorbidity was found to dramatically influence survival statistics and the evaluation of treatment effectiveness. A statistical technique known as conjunctive consolidation was used to incorporate comorbidity into the TNM staging system and maintain the four category system. Utilizing this technique, comorbidity was added to the TNM system for laryngeal cancer to create a composite staging system. Quantitative evaluation of the new system showed that the addition of comorbidity provides improved prognostic precision over TNM stage alone.