A systematic review of the prevalence of comorbid cancer and dementia and its implications for cancer-related care.

Objectives: A comorbid diagnosis of cancer and dementia (cancer-dementia) may have unique implications for patient cancer-related experience. The objectives were to estimate prevalence of cancer-dementia and related experiences of people with dementia, their carers and cancer clinicians including cancer screening, diagnosis, treatment and palliative care.Method: Databases were searched (CINAHL, Psychinfo, Medline, Embase, BNI) using key terms such as dementia, cancer and experience. Inclusion criteria were as follows: (a) English language, (b) published any time until early 2016, (c) diagnosis of cancer-dementia and (d) original articles that assessed prevalence and/or cancer-related experiences including screening, cancer treatment and survival. Due to variations in study design and outcomes, study data were synthesised narratively.Results: Forty-seven studies were included in the review with a mix of quantitative (n = 44) and qualitative (n = 3) methodologies. Thirty-four studies reported varied cancer-dementia prevalence rates (range 0.2%-45.6%); the others reported reduced likelihood of receiving: cancer screening, cancer staging information, cancer treatment with curative intent and pain management, compared to those with cancer only. The findings indicate poorer cancer-related clinical outcomes including late diagnosis and higher mortality rates in those with cancer-dementia despite greater health service use.Conclusions: There is a dearth of good-quality evidence investigating the cancer-dementia prevalence and its implications for successful cancer treatment. Findings suggest that dementia is associated with poorer cancer outcomes although the reasons for this are not yet clear. Further research is needed to better understand the impact of cancer-dementia and enable patients, carers and clinicians to make informed cancer-related decisions.