Prevalence and Global Factors Influencing Polypharmacy and its Clinical Phenotypes in Cancer Patients: A Systematic Review and Meta-Analysis

Background Polypharmacy (PP) is a rising morbidity among patients with a cancer diagnosis. Uncertainties remain regarding its exact burden, exact prevalence estimates, and definitional themes in this vulnerable cohort of patients. Methods Using PubMed, EMBASE, Scopus, the Cochrane Database of Systematic Reviews (CDSR), and Google Scholar, studies published between 2000 and 2025 were reviewed and critically appraised for eligibility and inclusion by two independent reviewers. Using random effect and quality effect models, pooled estimates of the prevalence of PP, prevalence by type of cancer, and geographical spread were determined. The prevalence rates of potentially inappropriate medications (PIMs) and drug-drug interactions (DDIs) were also estimated. Heterogeneity among the included studies was reported by corresponding I ² estimates. Results This meta-analytical review involved 24 studies comprising 110,052 participants. The overall pooled prevalence of PP among patients with cancer was 55% (95% CI: 47–62%) using the random effects model and 29% (95% CI: 12–49%) using the quality effects model. The overall heterogeneity among the included studies was significant ( I ²  = 100%, p < 0.001) for the random effects models. Conclusions The results from this meta-analysis revealed a high pooled prevalence estimates of polypharmacy among patient cohorts with cancer on the basis of marked variability in these estimates. Given this level of variability, the precise interventions capable of effectively reducing polypharmacy in these patient cohorts remain unclear. Future prospective and systematic studies are necessary to identify targeted strategies to mitigate polypharmacy and improve patient outcomes. Systematic review registration: PROSPERO, Number CRD42024576772 .