Background and objectives: Breast cancer is the most commonly diagnosed cancer in women and its mortality is increasing. Therefore, research to improve treatment is of paramount importance. One method of treatment is photodynamic therapy. Photodynamic therapy selectively stimulates apoptosis in photosensitizer-treated neoplastic breast cells as a result of cytotoxic singlet oxygen generation via collisions between triplet excited state photosensitizer and triplet ground state oxygen upon tissue irradiation. The aim of this study was to evaluate the effects of photodynamic action on cancerous breast tissue samples as a model of photodynamic therapy. Materials and Methods: Breast cancer tissue samples were obtained from post-operative material and the patterns of histopathological changes in breast cancer tissue before and after photodynamic action on post-chemotherapy tissue were evaluated. Excised tissue samples were obtained from 48 female breast cancer patients who had previously undergone chemotherapy. Breast cancer tissues for this study were taken from macroscopically visible tumors larger than 10 mm. Histopathological analysis was performed to evaluate any morphological changes prior to and after photodynamic action on the post-chemotherapy tissue samples. Eighteen breast cancer tissue samples were analyzed before chemotherapy, fifteen after chemotherapy, and fifteen samples were analyzed after chemotherapy and application of photodynamic action. The photosensitizer Rose Bengal was applied to the samples subjected to photodynamic action. Results: Photodynamic action on post-chemotherapy neoplastic tissue showed histological changes under a light microscope. The results showed that morphological changes in breast cancer tissues after chemotherapy and photodynamic action were dependent on the concentration of Rose Bengal. In all cases, follow-up imaging showed tumor shrinkage of an average of 35% from baseline size. Conclusions: Histopathological examination revealed photosensitizer-concentration-dependent changes after photodynamic action in excised post-chemotherapy tissue. The effects of photodynamic action observed in this study suggest that the application of photodynamic therapy after chemotherapy can aid in breast cancer cell eradication.
Keywords: breast cancer; histology; photodynamic therapy; photosensitizer.