In vivo Raman spectroscopy of breast tumors prephotodynamic and postphotodynamic therapy

Breast cancer is most fatal cancer among women worldwide. The high mortality can be attributed to late detection and low treatment efficacy. Treatment is difficult owing to the multitude of breast cancer subtypes and making decisions on therapeutic strategy difficult. A tool to predict treatment prognosis may greatly aid this decision making. Currently available prediction methods have low accuracy in addition to several other disadvantages. Of the several new techniques being investigated for prognosis prediction, Raman spectroscopy (RS) has the advantage of high sensitivity, rapidity, and amenability to in vivo applications, making it ideal for clinical translation. In this study, we have evaluated the biochemical changes posttherapy with respect to pretherapy using RS. In vivo Raman spectra acquired from live rat breast tumors (skin removed) without treatment, 24hr postphotosensitizer injection and 24hr after photodynamic therapy, were analyzed using multivariate principal componentlinear discriminant analysis. Relative increase in some spectral signatures associated with nucleic acids, amino acids, and proteins, especially collagen, were observed posttherapy; and pretherapy and posttherapy spectra could be classified with 100% efficiency. The ability of RS to detect these changes suggests possibility of deciphering spectral markers for prognostic applications in future.