Systematic Review and Meta-Analysis on the Associations of Polypharmacy and Potentially Inappropriate Medication With Adverse Outcomes in Older Cancer Patients

Abstract Background Both polypharmacy and potentially inappropriate medication (PIM) intake are highly prevailing in older cancer patients. However, only studies on the association of polypharmacy and postoperative complications have been meta-analyzed previously. Methods A systematic review and a meta-analysis of prospective/retrospective observational studies reporting associations of polypharmacy or PIM with at least one out of five predefined adverse health outcomes in a population of older cancer patients (≥60 years) were carried out. PubMed and Web of Science were used to search for relevant studies published between January 1991 and March 2020. Data were pooled by adopting a random-effects model. Results Overall, 42 publications were included in the systematic review. Meta-analyses could be performed on 39 studies about polypharmacy and 13 studies about PIM. Polypharmacy was found to be statistically significantly associated with all-cause mortality (risk ratio [95% confidence interval]: 1.37 [1.25–1.50]), hospitalization (1.53 [1.37–1.71]), treatment-related toxicity (1.22 [1.01–1.47]), and postoperative complications (1.73 [1.36–2.20]). The association of polypharmacy with prolongation of hospitalization was not statistically significant at the p < .05 significance level (1.62 [0.98–2.66]). With respect to PIM, a statistically significant association with all-cause mortality (1.43 [1.08–1.88]) was observed but not with other adverse outcomes. Conclusions Polypharmacy was found to be associated with several adverse outcomes and PIM use with all-cause mortality in older cancer patients. However, these results should be interpreted with caution because about three-quarters of the studies identified did not adjust for comorbidity and are prone to confounding by indication.