Revolutionizing breast cancer monitoring: emerging hematocrit-based metrics - a narrative review

Breast cancer remains a leading global health concern, with significant strides made in early detection and treatment. However, effective long-term surveillance, particularly for recurrence and metastasis, remains a clinical challenge. Traditional methods like imaging and biopsy are often invasive, costly, and have limited sensitivity in detecting subtle changes during disease progression. Emerging evidence suggests that hematocrit-based metrics - measurements of the proportion of red blood cells (RBCs) in blood - could serve as valuable, minimally invasive biomarkers for monitoring breast cancer. This review highlights recent advancements in hematocrit-focused research and its potential role in revolutionizing breast cancer surveillance. Hematocrit dynamics reflect complex physiological processes influenced by cancer biology, including inflammation, angiogenesis, and treatment-induced bone marrow suppression. Alterations in hematocrit levels have been associated with prognostic outcomes, treatment responses, and early indications of recurrence in breast cancer patients. Coupled with other hematological and molecular markers, hematocrit offers a cost-effective and readily accessible tool to track disease status in real time. Recent technological innovations, such as point-of-care testing, artificial intelligence-driven data analysis, and microfluidic devices, are further advancing the applicability of hematocrit-based metrics in both clinical and remote monitoring settings.