Hematoporphyrin derivative phototherapy (HpD-PT) is currently being used experimentally in the treatment of various
malignancies. The effectiveness of HpD-PT appears to be limited to superficial
malignancies because of its inability to penetrate more than 0.5-1 cm. The mechanism of action has been demonstrated to result from the formation of toxic
singlet oxygen and other
oxygen radicals. Preliminary work suggested that the addition of other chemical agents known to produce toxic
oxygen radicals may enhance the effect of HpD-PT. To test this hypothesis, we examined the effectiveness of HpD-PT in the Walker 256
carcinosarcoma with and without
Adriamycin.
Tumor kill was estimated by calculating the area of
necrosis on photomicrographic sections. From this area, a radius of
tumor necrosis was determined and compared among various control and experimental groups. HpD-PT was effective in this model when compared to control groups (radius of
necrosis 3.79 +/- 0.97 mm vs. 2.60 +/- 1.26 mm, P less than .05). The addition of
Adriamycin significantly increased the radius of
necrosis when compared to HpD-PT (4.57 +/- 1.70 mm vs. 3.69 +/- 0.97 mm, P less than .01). From this work we conclude that HpD-PT demonstrates effective
tumor killing in this murine model. The addition of
Adriamycin significantly increased
tumor kill.