Photothermic treatment of pigmented B16 melanoma using a broadband pulsed light delivery system

Pulsed photothermic treatment (PTT) of pigmented B16 mice melanoma tumors was carried out using a Photodyne® incoherent light delivery system. Tumor heating with average temperature of 41–44°C was observed during broadband photoirradiation (600–800 nm) at light doses of 60–120 J/cm2 delivered using 0.6 J/cm2 pulses (2 ms) at 1 Hz repetition rate. Electron microscopy of tumor samples revealed pronounced structural changes in microvasculature and melanosomes. Pulsed PTT caused damage to endothelial cells and vascular walls, swelling of mitochondria and melanosomal disruption without nuclear alteration. Significant tumor response with necrosis formation followed by tumor regression was observed by a tumor growth study after PTT at 120 J/cm2.