Importance of Comorbidity in Head and Neck Cancer

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Abstract
Patients with head and neck cancer are staged according to the morphology of the tumor with little or no attention given to the importance of the other diseases, illnesses, or conditions. These other conditions are generally referred to as comorbidities. Although not a feature of the cancer itself, comorbidity is an important attribute of the patient with cancer. Comorbidity has direct impact on the care of patients, selection of initial treatment, and evaluation of treatment effectiveness. The objective of this thesis is to demonstrate the importance of comorbidity in head and neck cancer. Specifically, the aims are 1) to demonstrate the burden of comorbidity among head and neck cancer patients by comparing the incidence of none, mild, moderate, and severe comorbidity among patients with head and neck cancer to patients with cancers of the colorectum, lung, breast, gynecological sites, or prostate, 2) to demonstrate the independent impact of comorbidity on overall survival, and 3) to demonstrate the importance of comorbidity in the assessment of initial treatment effectiveness. This was a prospective cohort study of the impact of comorbidity on head and neck cancer patients presenting for treatment between January 1995 and December 1996. In 1994, the author trained cancer registrars at an academic teaching hospital to code comorbidity from the medical record of new patients using a standard comorbidity index. Standard statistical techniques, including multivariable analysis, were used to compare and contrast the burden of comorbidity for patients with different cancers. Life survival techniques and multivariable logistic regression analysis were used to assess the independent prognostic impact of comorbidity. Further, the technique of conjunctive consolidation was used to augment the TNM system with comorbidity information, to more completely assess the impact of different initial treatments for patients with head and neck cancers. The cohort consisted of 3,378 patients with cancers of the head and neck (341), colorectum (307), lung (655), breast (483), gynecological sites (482), and prostate (1,110). The percentage of head and neck cancer patients with moderate to severe comorbidity was 21%; this degree of comorbidity burden was second only to patients with lung (40%) and colorectal (25%) cancer. There was a significant relationship between severity of comorbidity and overall survival (log-rank test, chi2 = 15.75; P < .0013). For cancers of the head and neck, lung, breast, and prostate the prognostic significance of comorbidity remained even after controlling for other factors, such as age and TNM stage. The results of this study show that comorbidity is an important feature of patients with head and neck cancer. Valid instruments exist to measure and classify the overall severity of comorbidity. The scientific evaluation of treatment and the care of patients are impeded by a rigid adherence to a staging system based solely on morphological descriptions of the cancer while ignoring suitable descriptions of the patient. The author believes that the addition of comorbidity information will improve the value of cancer statistics and the care of cancer patients.