<p>Cancer continues to pose a significant global health burden, driving the demand for more precise diagnostic and therapeutic approaches. This review highlights the rapid evolution of biosensor technologies and their expanding role in oncology starting from early cancer detection to advanced drug delivery systems. Traditional treatments, while foundational, often suffer from limitations such as non-specific toxicity and therapeutic resistance. In contrast, biosensors offer high sensitivity, specificity, and real-time detection capabilities, enabling accurate monitoring of cancer biomarkers. For example, electrochemical biosensors based on aptamer-functionalized nanomaterials have demonstrated femtomolar detection limits for biomarkers like carcinoembryonic antigen (CEA) and HER2/neu. Emerging wearable biosensors and AI-integrated point-of-care systems now enable continuous monitoring of circulating miRNAs, ctDNA, and exosomes in patient biofluids. We present an in-depth analysis of various biosensor platforms, including electrochemical, optical, microfluidic, nanomaterial-enhanced, and metal–organic framework (MOF)-based systems. Particular focus is given to label-free and nucleic acid-based biosensors designed for microRNA (miRNA) detection, which are proving critical in early-stage cancer diagnostics. Quantitative performance metrics such as sensitivity (&gt; 90%), specificity, and detection thresholds (as low as 8&#xa0;fg/mL in clinical samples) are discussed for key biosensor models. Additionally, we explore the integration of biosensors into smart drug delivery systems, emphasizing nanotechnology's role in improving targeted therapeutic outcomes. The review concludes with insights into emerging directions such as liquid biopsy techniques, artificial intelligence-assisted diagnostics, and precision medicine. Collectively, these innovations position biosensors as essential tools in the future landscape of personalized and efficient cancer care.</p> Graphical Abstract <p></p>