Photodynamic therapy for the treatment of metastatic lesions in bone: Studies in rat and porcine models.

This study represents the first reported use of photodynamic therapy in bone and specifically, as a treatment for spinal metastases. A metastatic model in rat confirmed the efficacy of benzoporphyrin derivative-monoacid-mediated PDT for treating lesions within the spine and appendicular bone. Fluorimetry confirmed the selective accumulation of drug into the tumor(s) at 3 hours post-injection. 48 hrs post light delivery into the vertebral body of the rat spine loss of bioluminescent signal and histological analyses of sectioned spine confirmed MT-1 tumor cell kill in vivo as previously confirmed in vitro using an established cell viability assay. Porcine vertebrae provided a model comparable to that of human for light propagation and PDT response. Light measurements were recorded at 2.5 mm increments as the detector probe was retracted out of the vertebral body away from a diffusing fiber at 70-90degrees planar angle to it. At 30 minutes or 1hr post BPD-MA administration (6 mg/m(2)), light (648 J, 150 mW/cm, 690 mn) was delivered to vertebrae L1 and/or L2. Vertebrae were harvested and sectioned for histology 48 hrs following PDT. Light propagation was plotted as distance (mum) from the emitting source. Results support the application of PDT to the treatment of primary or metastatic lesions within bone.