Hematological Profiles and Serum Cytokine Levels in Patients With Breast Cancer in Low‐ and Middle‐Income Countries: A Systematic Review and Meta‐Analysis of Current Evidence

Background and Aim Breast cancer is a leading cause of morbidity and mortality in Low‐ and Middle‐Income Countries (LMICs). Hematological and inflammatory markers offer accessible, low‐cost tools for patient assessment; hence, this study synthesized evidence on hematological parameters and serum cytokine levels in breast cancer patients from LMICs. Methods Following PRISMA guidelines, we searched PubMed, Scopus, and Google Scholar for studies published between January 2013 and December 2025 comparing hematological parameters or serum cytokine levels between breast cancer patients and controls in LMICs, the protocol was registered on PROSPERO (CRD420261543115). Of 25 eligible studies identified, 22 were included in the meta‐analysis. Data on complete blood count indices and inflammatory cytokines were extracted and pooled using random‐effects models. Pooled effect sizes were calculated as standardized mean differences (SMD) with 95% confidence intervals. Subgroup analyses were performed by treatment status, and heterogeneity, sensitivity, and publication bias were assessed. All statistical analyses were performed using R software (version 4.5.0). Results Erythrocyte parameters were consistently lower, including red blood cell count (SMD = −1.83; 95% CI: −3.32 to −0.33), packed cell volume (SMD = −4.04; 95% CI: −8.08 to −0.00), mean corpuscular volume (SMD = −1.15; 95% CI: −2.64 to −0.34), and mean corpuscular hemoglobin (SMD = −0.99; 95% CI: −2.19 to −0.20). Platelet‐related parameters were elevated, including pretreatment platelet count (SMD = 0.44; 95% CI: 0.17–0.70) and mean platelet volume (SMD = 0.44; 95% CI: 0.07–0.81). Leukocyte profiles showed decreased lymphocytes (SMD = −1.07; 95% CI: −1.82 to −0.83) and eosinophils (SMD = −2.33; 95% CI: −5.90 to −1.25), with increased monocytes (SMD = 0.79; 95% CI: 0.29– 1.29). One study reported markedly elevated inflammatory cytokines in patients versus controls: IL‐6 (20.6 vs. 4.4 pg/mL), IL‐10 (8.8 vs. 2.8 pg/mL), and TNF‐α (26.0 vs. 4.7 pg/mL); all p = 0.001. Conclusion These findings support the integration of routine complete blood count parameters as accessible, low‐cost tools for monitoring disease burden and systemic inflammation in resource‐limited settings. Further research is needed to characterize cytokine profiles and establish normative reference data for LMIC populations.