Optimization of brain photodynamic therapy : a study of extended-time low-fluence-rate ALA-photodynamic therapy in a rat glioma mode

The importance of the rate of light delivery and the length of photodynamic therapy as an alternative treatment modality for brain glioma have been investigated and shown that optimized PDT regimens would have the potential to reduce the tumor recurrence and the treatment-induced morbidity. In a rat glioma model, using photosensitizer ALA-PpIX, we further investigated the effect of extended-time low-fluence-rate PDT on the number of apoptotic, necrotic, surviving, and infiltrated tumor cells, associated with three fluence rates of 0.5, 1.0, and 1.5 mW cm⁻², each at three treatment lengths of 24, 48, and 72 hours. Our results demonstrated that lowest fluence rate used in our study has an improved apoptosis to necrosis ratio; however higher fluence rates show a clear supremacy for tumor control in shorter treatment times. Therefore, low-fluence-rate brain ALA-PDT may only be more beneficial for tumor control at longer treatment periods.