[Combination effect of photodynamic therapy and microwave hyperthermia on experimental squamous cell carcinoma in...

We investigated the time course of Hematoporphyrin oligomer (HpO) uptake to squamous cell carcinoma (SCC) transplanted into C3H mice after intraperitoneal (i.p.)-injection by measuring its fluorescence intensity. The fluorescence intensity was maximum at 83 hr after the i.p.-injection. The tumors once disappeared by the single application of photodynamic therapy (PDT) or microwave hyperthermia at 83 hr after HpO i.p.-injection. However, all the tumors treated with these single modalities recurred within 4 weeks after the treatments. Therefore, we investigated the therapeutic effect of microwave hyperthermia in combination with PDT at 83 hr after HpO i.p.-injection. As the results, the combination effect was the strongest when high-dose therapy was used as the first choice of therapy, irrespective of the orders of the treatments and no tumor regrowth occurred over 45 days after tumor disappearance.