Photodynamic therapy of orthotopic prostate cancer with benzoporphyrin derivative: Local control and distant metastasis

This is the first report of photodynamic therapy (PDT) in an orthotopic pro state tumor model and shows that PDT combined with surgery (tumor bed steri lization) gave significant local control of the primary tumor and significa nt reduction in distant metastases. By contrast, either treatment alone (su rgery or PDT) gave relatively poorer local control, and PDT gave a signific ant increase in the mean number of lung metastases, The MatLyLu variant of the Dunning 3327 rat prostate cancer cell line, which has been selected to be metastatic to lymph nodes and lungs, was injected into the ventral lobe of the rat prostate. After 7 days, tumors were either treated by surgical r emoval of the ventral lobe, PDT with liposomal benzoporphyrin derivative mo noacid ring A, or a combination of surgery, followed by PDT of the tumor be d. Results after 21 days showed a reduction in prostate tumor weight in all groups compared with controls, which became highly significant only for th e combination group (17% of control mean tumor weight; P < 0.001; 7 of 13 c linical complete responses). The combination treatment also led to a reduct ion in lymph node metastasis and reductions in both the frequency and mean number of lung metastases compared with other treatment groups. The PDT-alo ne group, however, had a mean number of lung metastases per animal, which w as nine times the control group and 34 times the combination group. These f indings suggest that a tumor bed sterilization approach may be promising fo r locally advanced prostate cancer and suggest that factors other than loca l control may need to be evaluated when considering PDT for primary prostat e cancer.