Cancer and comorbidity: redefining chronic diseases

A narrow subspecialty model of cancer care has led to cancer treatment often being given outside the full medical context of the patient. The full range of comorbid illness must be considered in all aspects of diagnosis and treatment. This study was conducted to describe the prevalence of comorbidity in cancer patients and examine its relation with multiple demographic and clinical variables.

A case comparison study of 15,626 population-based incident cases of cancer was conducted between 1984-1992 in 3 metropolitan Detroit counties (a National Cancer Institute Surveillance, Epidemiology, and End Results program). Chronic disease status and demographics were collected by self-report; cancer diagnoses and staging were obtained by medical record review. Univariate and multiple logistic regression analyses were performed.

Comorbidity was present in 68.7% of cancer patients, and 32.6% of these individuals had > or = 2 comorbid conditions. Frequency was increased in the elderly, African-American patients (particularly African-American women), smokers, and those with lower socioeconomic status. Rates also appeared to vary by specific tumor site.

Comorbid chronic diseases are common in persons with cancer. The prevalence of comorbidities has important clinical, health service, and research implications. The disease specific model of oncology may limit appropriate care for these patients, and enhanced integration of primary care into the ongoing management of cancer may offer better outcomes.