Comorbid Disease and Cancer: The Need for More Relevant Conceptual Models in Health Services Research

Theadverseconsequencesofcomorbidityposeamajor clinical challenge in the care of older cancer patients. While the burden of comorbidity is clearly a major prognostic factor for long-term survival, the underlying mechanisms are not well understood. Health services research that focuses on specific comorbidities and their effects in a cancer patient’s clinical trajectory can produce new insights into the optimal diagnosis, treatment, and long-term surveillance of cancer patients with comorbid disease. This information can then be used to design interventions that improve prognosis. We propose a conceptual model of comorbidity and cancer that can guide this research. The model illustrates the potential impact of a specific comorbidity at multiple points of a patient’s clinical trajectory, from cancer detection through diagnosis and treatment. Comorbid illness is a significant concern in patients with cancer. 1,2 For example, patients with severe underlying chronic obstructive pulmonary disease are not good candidates for resection of a lung malignancy, and therefore their chance of cure is decreased. 3,4 Similarly, a diagnosis of congestive heart failure precludes some cancer treatments. 5,6 Comorbid disease is also a competing cause of death. This is particularly true for older patients with cancer, who comprise the majority of new cancers diagnosed.