As populations age, the prevalence of both chronic diseases in general and cancer specifically increase. Comorbidity is therefore common in elderly cancer patients. This presentation summarises evidence relating to how comorbidity is related to cancer, and outlines issues to be addressed in the Cancer Care in the context of Comorbidity symposium.  An extensive review of over 200 relevant papers was used to inform this overview.

Comorbidity is common among cancer patients primarily because cancer shares many risk factors with other medical conditions including age.  The prevalence of any comorbidity among cancer patients varies depending on the measure of comorbidity used, population studied and cancer site(s) under investigation, but most prevalence estimates range between 50-70%. The most common concomitant conditions are hypertension, respiratory disease, heart disease, cerebrovascular disease, previous cancer, arthritis and diabetes.

There are two non-mutually exclusive hypotheses, both with some supporting evidence, relating to the role of comorbidity on cancer diagnosis: one hypothesis suggests earlier diagnosis because those with comorbidity experience increased medical surveillance generally, the other suggests delayed diagnosis because health professionals and patients are distracted by their concomitant diseases so symptoms of cancer go unnoticed. 

Research consistently shows that those with comorbidity are less likely to receive definitive treatment, even when that treatment is likely to be beneficial. While there is evidence that some cancer patients with comorbidity are at increased risk of post-therapeutic complications, this is far from a consistent finding. Evidence suggests that comorbidity exacerbates inequities in cancer outcomes for some population groups, and may provide one pathway through which inequities are addressed.

Finally, comorbidity has a clear and demonstrable adverse effect on cancer survival and cost of care across every site studied. It is also likely to negatively impact the quality of life of cancer patients.