Enhanced Susceptibility of Mouse Squamous Cell Carcinoma to Photodynamic Therapy Combined With Low-Dose Administration of Cisplatin

PurposeWe have investigated the antitumor effect of photodynamic therapy (PDT), using Photofrin as the photosensitizer, combined with low-dose cisplatin (CDDP) on NR-S1 mouse squamous cell carcinoma.Materials and MethodsCDDP (5 mg/kg body weight) was injected intraperitoneally either 1 hour or 3 hours prior to PDT or immediately afterward. Twenty-four hours after each protocol, the antitumor effects were evaluated by percentage area of the tumor necrosis in hematoxylin-eosin stained specimens as well as terminal deoxynucleotidyl transferase-mediated d-UTP nick-end labeling indices. Furthermore, the tumor sizes were evaluated at 3, 7, and 10 days after each protocol.ResultsThe antitumor effect of PDT was enhanced by administration of CDDP 3 hours before PDT, whereas the administration of CDDP 1 hour before PDT or immediately after PDT did not potentiate a PDT antitumor effect.ConclusionAdministration of low-dose CDDP 3 hours before PDT appears to be a useful treatment modality.