Comorbidities and cancer

A comorbidity is a non cancer health condition which in cancer patients are associated with poorer outcomes, a higher risk of mortality and postoperative complications, and a decreased likelihood of completing a course of treatment or receiving standard treatment. Comorbidities are of particular interest as understanding comorbidities and the impact they have on cancer patients is essential in order to improve patient health and outcomes.

In order to understand the impact of comorbidities on cancer patients the comorbidities need to be identified and measured.

The Charlson Comorbidity Score, a method of measuring comorbidity, was first developed in 1987. This was a weighted score that took into account the number and seriousness of comorbid disease, to predict mortality within 1 year of hospitalisation.  Each comorbid condition, based on the International Classification of Disease (ICD) diagnosis codes found in administrative data such as hospital data, was assigned a weight from 1 to 6, based on the estimated 1-year mortality hazard ratio from a Cox proportional hazards model. These weighted components were then summed to produce the overall Charlson comorbidity score.

Following on from that Quan and others [note 1] codified the disease conditions by ICD-10 group. NDRS has now adapted these codes into an algorithm that produces the Charlson scores each year from HES data linked to cancer registration data. These Charlson scores are used by NDRS analysts to better understand cancer outcomes. For example, mortality rates for patients in different geographic areas or under the care of different healthcare providers are often adjusted to take account of the underlying levels of population co-morbidity, to better understand the impact of cancer specifically on patient health.  The Charlson scores are also available to researchers and service users through the DARS process, linked to other patient level data sets.

Notes:

1. Quan H and others. Coding algorithms for defining comorbidities in ICD-9-CM and ICD-10 administrative data. November 2005: volume 43 issue 11 pages 1130-9 [viewed on 31 March 2022]