Photodynamic therapy is a promising cancer treatment that employs wavelength-specific light in combination with a photosensitizing agent to induce local tumor destruction by photochemical generation of cytotoxic singlet oxygen. Clinical PDT has been evaluated for a variety of primary tumors, however, its use in spinal metastases to our knowledge has not been previously evaluated. A practical consideration is the ability to deliver light to bone. The investigators are evaluating a novel method of applying light to targeted spinal lesions using a minimally invasive technique similar to percutaneous vertebroplasty. This preliminary preclinical study evaluates the feasibility and efficacy of spinal PDT. To evaluate the feasibility and efficacy of spinal meta-static photodynamic therapy (PDT) using a percutaneous minimally invasive surgical approach similar to that of vertebroplasty in a preclinical model of bone metastases. A bioluminescent metastatic model was developed (intracardiac injection 2x106 MT-1Luc human breast cancer cells; Spinal PDT caused a reduction in bioluminescence of targeted lesions (66% to 87% in three hour drug-light group using light fluence rates of 25J and 150J, respectively; p<
0.05). The most selective drug-light interval was twenty-four hours where PDT induced tumor cell apoptosis/necrosis occurred, however, no spinal cord injury was observed. The greatest anti-tumor effect was observed at the three hour drug-light interval but observations of neurologic sequalae (9/22 animals) highlight the importance of ongoing study to closely define the therapeutic window of PDT. Drug dosimetry and the drug-light interval are critical in establishing an efficacious and safe treatment range for spinal PDT. Bioluminescent reporter imaging provides an