Preclinical Study

Breast Cancer Research and Treatment

, Volume 119, Issue 2, pp 325-333

First online:

Defining the therapeutic window of vertebral photodynamic therapy in a murine pre-clinical model of breast cancer metastasis using the photosensitizer BPD-MA (Verteporfin)

  • Margarete K. AkensAffiliated withDivision of Orthopaedic Surgery, Sunnybrook Health Science Centre Email author 
  • , Michael R. HardistyAffiliated withDivision of Orthopaedic Surgery, Sunnybrook Health Science Centre
  • , Brian C. WilsonAffiliated withOntario Cancer Institute
  • , Joerg SchwockAffiliated withOntario Cancer Institute
  • , Cari M. WhyneAffiliated withDivision of Orthopaedic Surgery, Sunnybrook Health Science Centre
  • , Shane BurchAffiliated withDepartment of Orthopaedic Surgery, University of California
  • , Albert J. M. YeeAffiliated withDivision of Orthopaedic Surgery, Sunnybrook Health Science Centre

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Breast cancer is known to cause metastatic lesions in the bone, which can lead to skeletal-related events. Currently, radiation therapy and surgery are the treatment of choice, but the success rate varies and additional adjuncts are desirable. Photodynamic therapy (PDT) has been applied successfully as a non-radiative treatment for numerous cancers. Earlier work has shown that the athymic rat model is suitable to investigate the effect of PDT on bone metastasis and benzoporphyrin-derivative monoacid ring A (BPD-MA; verteporfin) has been shown to be a selective photosensitizer. The aim of this study was to define the therapeutic window of photosensitizer with regard to drug and light dose. Human breast carcinoma cells (MT-1)—stable transfected with the luciferase gene—were injected intra-cardiacally into athymic rats. At 14 days, the largest vertebral lesion by bioluminescence imaging was targeted for single treatment PDT. A drug escalating-de-escalating scheme was used (starting drug dose and light energy of 0.2 mg/kg and 50 J, respectively). Outcomes included 48 h post-treatment bioluminescence of remaining viable tumour, histomorphometric assessment of tumour burden, and neurologic evaluation. The region of effect by bioluminescence and histology increased with increasing drug dose and light energy. A safe and effective drug-light dose combination in this model appears to be 0.5 mg/kg BPD-MA and applied light energy of less than 50 J for the thoracic spine and 1.0 mg/kg and 75 J for the lumbar spine. For translation to clinical use, it is an advantage that BPD-MA (verteporfin), a second-generation photosensitizer, is already approved to treat age-related macular degeneration. Overall, PDT represents an exciting potential new minimally-invasive local, safe and effective therapy in the management of patients with spinal metastases.


Spine Breast cancer Bone metastasis Photodynamic therapy