Label-free molecular profiling of cancer using Raman spectroscopy: from fundamentals to clinical applications

Early cancer detection and individualized therapy represent two of the foremost challenges in contemporary oncology. Raman spectroscopy, a rapid and label-free technique based on molecular vibrations, has emerged as a powerful tool with significant potential to address these needs. It offers unique capabilities for early cancer detection, real-time histopathological evaluation, tumor classification, and intraoperative diagnosis. This article reviews the fundamental principles of spontaneous Raman spectroscopy and highlights recent advances in enhanced Raman techniques, including coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS). We examine their applications in diagnosing cancers of the lung, liver, colorectum, gastrointestinal tract, and other solid tumors, with a focus on early cancer detection, real-time histopathological evaluation, and label-free tissue characterization. Furthermore, we explore the use of Raman spectroscopy in studying tumor metabolic profiles and the tumor microenvironment, such as extracellular matrix (ECM) profiling, enabling new insights into metabolic imaging and vibrational phenotyping. The review also addresses key technical and translational challenges in Raman-based cancer diagnosis-including signal enhancement, spectral unmixing, instrument miniaturization, and clinical interpretability. Finally, we outline future directions for developing integrated, multimodal diagnostic platforms that combine vibrational spectroscopy with other optical methods. These advances hold great promise for achieving real-time, precise, and personalized cancer management.