Water-filtered infrared-A radiation: a novel technique for localized hyperthermia in combination with bacteriochlorophyll-based photodynamic therapy.

A novel application of an infrared-A (IR-A) radiation source equipped with a water-filter in the radiation path is described, which allows for tumour treatment with a simultaneous combination of localized hyperthermia (HT) and bacteriochlorophyll-serine (Bchl-ser) based photodynamic therapy (PDT). Using this system, the IR-A radiation was used to heat tumours to 43 degrees C for 60 min, while at the same time activating the Bchl-ser which was injected i.v. at a dose of 20 mg/kg, 10 min following commencement of HT. The growth of tumours undergoing this combined therapy was compared to that of tumours undergoing HT alone or sham-treated controls. Within the 90 day observation period, 100% of tumours in sham-treated animals, 80% in HT-treated animals and only 17% in HT + Bchlser-treated animals reached the end point target volume of 3.5 ml. Thus, the tumour growth inhibition effect of HT can be substantially enhanced by combination with Bchl-ser-PDT. This novel technique has proved to be well-tolerated, easy to apply and should be suitable for treatment of superficial malignancies, especially where hypoxic tumour areas are present.