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It is estimated that metastasis is responsible for about 90% of cancer deaths. Therefore, the effective control of tumor progression and metastasis is crucial to decrease the patient mortality rate. The searching for effective regimens has become one of the hot research topics. Photodynamic therapy (PDT) has shown very promising in local control of pancreatic tumors, but had little impact in reducing tumor metastasis. We have been actively investigating the PDT-based combination treatment efficacies in orthotopic mouse models of human pancreatic cancers, and had previously found and reported that PDT followed by 4-time administrations with chemotherapeutic adjuvant abraxane could dramatically shrink primary pancreatic tumors, some of which even disappeared from the pancreas. In this study, we focused on the evaluation of treatment responses on metastasis inhibition with the same treatment regimen after two periods of time: short-term (24 days) and mid-term (60 days). The treatment regimen had the most suppressive effect on metastasis as compared with other control groups: 1) PBS, 2) Gemcitabine, 3) PDT, 4) abraxane, and 5) Gemcitabine + abraxane in both AsPC-1 and MIA PaCa-2 cell line models and for the short- and mid-term experimental courses. However, the triple combination therapy (this treatment regimen plus Gemcitabine) could not further increase the metastasis inhibition. Regression analysis for tumor weights and metastasis burden in any of the corresponding treatment groups suggested that there might not be a correlation between tumor size and metastasis, and the metastasis decrease might not be the results of tumor decrease upon the treatments.
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