Impact of comorbidity on short-term mortality and overall survival of head and neck cancer patients
Background. In 2001, we presented a Cox regression model that is able to predict survival of the newly diagnosed patient with head and neck squamous cell carcinoma (HNSCC). This model is based on the TNM classification and other important clinical variables such as age at diagnosis, sex, primary tumor site, and prior malignancies. We aim to improve this model by including comorbidity as an extra prognostic variable. Accurate prediction of the prognosis of the newly diagnosed patient with head and neck cancer can assist the physician in patient counseling, clinical decision-making, and quality maintenance. Methods. All patients with HNSCC of the oral cavity, pharynx, and larynx diagnosed in the Leiden University Medical Centre between 1981 and 1998 were included. From these 1371 patients, data on primary tumor site, age at diagnosis, sex, TNM classification, and prior malignancies were already available. Comorbidity data were collected retrospectively according to the ACE27 manual. The prognostic value of each variable on overall survival was studied univariately by Kaplan-Meier curves and the log-rank test. The Cox regression model was used to investigate the impact of these variables on overall survival simultaneously. Furthermore, univariate analyses were performed to investigate the impact of comorbidity severity on short-term mortality and to investigate the impact of organ-specific-comorbidity on short-term mortality. Results. Comorbidity was present in 36.4% of our patients. Mild decompensation was seen in 17.4%, moderate decompensation in 13.5%, and severe decompensation in 5.5%. Most frequently observed ailments were cardiovascular, respiratory, and gastrointestinal. In univariate analyses, all prognostic variables, including comorbidity, contributed significantly to overall survival. Their contribution (except sex) remained significant in the multivariate Cox model. Internal validation of this model showed a concordance index of 0.73, indicating a good predictive value. Short-term mortality was seen in 5.7% of our patients. Cardiovascular comorbidity, respiratory comorbidity, gastrointestinal comorbidity, and diabetes showed a significant relationship with short-term mortality. Conclusions. Comorbidity impacts overall survival of the newly diagnosed patient with HNSCC. There is a clear distinction between the impact of the 4 ACE27 severity grades. The impact of an ACE27 grade 3 is comparable to the impact of a T4 tumor or an N2 neck. Comorbidity impacts short-term mortality as well. Especially cardiovascular comorbidity, respiratory comorbidity, gastrointestinal comorbidity, and diabetes show a strong relationship.