Prevalence of pre-existing cognitive impairment in patients treated for cancer and the impact of cancer treatment on cognitive outcomes: A scoping review

Abstract

Introduction

Pre-existing cognitive impairment (CI) is likely underreported in patients treated for cancer, and its prevalence remains unclear. Older adults with CI may have a greater risk of treatment failure and increased morbidity and mortality than patients with intact cognition. To our knowledge, there has not been a previous review summarizing data on the prevalence of pre-existing CI in patients with cancer. This review addresses: (1) What is the prevalence of pre-existing CI in patients treated for cancer and (2) What is the impact of cancer treatment on cognitive outcomes among patients exhibiting pre-existing CI before planned cancer treatment?

Materials and Methods

We defined CI as a diagnosis of dementia or mild or unspecified CI before any cancer treatment, including surgery. This scoping review followed the Arksey and O'Malley framework and adhered to Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews guidelines. Two reviewers independently screened titles, abstracts, and full-text articles, resolving disagreements with a third reviewer. The reviewers systematically searched MEDLINE, Excerpta Medica Database (EMBASE), and Cumulative Index to Nursing and Allied Health Literature (CINAHL) from inception until July 15, 2023, including original research focused on participants aged 60 or older reporting the prevalence of pre-existing CI before any cancer treatment.

Results

Among the 10,490 screened citations, 23 manuscripts reporting on 21 studies met the inclusion criteria for both review questions. Pre-existing CI was prevalent at a mean rate of 6 % in administrative database studies, while clinical studies employing pre-treatment cognitive screening tools, primarily the Mini-Mental State Examination and Mini-Cog, reported a higher mean prevalence of 26 % (range 2.6 to 52 %). Only one study reported postoperative delirium in 27.9 % of patients with CI following cancer surgery, suggesting a higher risk of delirium in this population. However, none of the reviewed studies provided data on other cognitive outcomes, such as chemotherapy-related CI or treatment toxicity, in these individuals.

Discussion

Pre-existing CI is common but highly variable. The variability in reported prevalence rates can largely be attributed to significant differences in study inclusion criteria of participants and sample size, with some studies relying on regionally limited datasets.