A number of indices exist that allow doctors to determine the combined impact of numerous illnesses on survival outcomes, which aids in treatment decision-making. Disease-specific comorbidity measures have been created for certain tumor types, including breast cancer and head and neck cancer, but the most commonly used general measure is the Charlson Comorbidity Index.
Created in 1987, the Charlson index includes 19 categories of disease that are “weighted” at 1, 2, 3 or 6 based on their association with mortality. Points are added based on the patient’s age—one point for each decade starting at age 50. The patient’s comorbidity score is the sum of the age and all comorbidity weights. As the score increases, so does the burden of the various illnesses.
Physicians may apply a different comorbidity measure first introduced in 2000 that is specific to cancer patients. The Adult Comorbidity Evaluation 27 (ACE-27) involves the review of a patient’s medical records in order to determine the presence and severity of 27 illnesses, which are then ranked as mild (grade 1), moderate (grade 2) or severe (grade 3). An overall comorbidity score is calculated based on the highest ranked condition. For instance, if two or more moderate illnesses occur in different disease groupings, the overall score is designated as severe.
While these and other methods to determine the severity of coexisting illnesses have prognostic usefulness to the patient and physician, the lack of specificity means more research must still be done.