The Impact of Cognitive Impairment on Treatment Toxicity, Treatment Completion, and Survival among Older Adults Receiving Chemotherapy: A Systematic Review

SIMPLE SUMMARY: Although cognitive impairment is common among older adults, the relationship between cognitive impairment and its effect on cancer outcomes is unclear. We conducted a systematic review of the literature to examine how toxicity risk, treatment completion, and survival may be impacted by chemotherapy in patients exhibiting evidence of cognitive impairment. Despite an absence of clear parallels between the severity of cognitive impairment and cancer outcomes, we found statistically significant relationships with survival in several studies and with toxicity in one study. An overall lack of robust evidence indicates the need for further research on the role of cognitive impairment in predicting survival, treatment completion, and toxicity among older adults receiving chemotherapy. ABSTRACT: Cognitive impairment (CI) is common among older adults with cancer, but its effect on cancer outcomes is not known. This systematic review sought to identify research investigating clinical endpoints (toxicity risk, treatment completion, and survival) of chemotherapy treatment in those with baseline CI. A systematic search of five databases (inception to March 2021) was conducted. Eligible studies included randomized trials, prospective studies, and retrospective studies in which the sample or a subgroup were older adults (aged ≥ 65) screened positive for CI prior to receiving chemotherapy. Risk of bias assessment was performed using the Quality in Prognosis Studies (QUIPS) tool. Twenty-three articles were included. Sample sizes ranged from n = 31 to 703. There was heterogeneity of cancer sites, screening tools and cut-offs used to ascertain CI, and proportion of patients with CI within study samples. Severity of CI and corresponding proportion of each level within study samples were unclear in all but one study. Among studies investigating CI in a qualified multivariable model, statistically significant findings were found in 4/6 studies on survival and in 1/1 study on nonhematological toxicity. The lack of robust evidence indicates a need for further research on the role of CI in predicting survival, treatment completion, and toxicity among older adults receiving chemotherapy, and the potential implications that could shape treatment decisions.