Photodynamic therapy of C3H mouse mammary carcinoma with haematoporphyrin di-ethers as sensitizers.

Haematoporphyrin di-ethers were synthesized and tested as sensitizers for photodynamic therapy of C3H/Tif mammary tumours in mice. Growth curves of the tumours were determined by measuring the tumour volume. The animals were given 25 mg porphyrins kg-1 body weight i.p. and 24 h later exposed to 135 J cm-2 of 630 nm light at a fluence rate of 150 mW cm-2. The sensitizing efficiency of the ethers was measured in terms of the increase in growth time of the treated tumours, as compared with that of untreated controls, needed to reach a volume 5 times larger than that at the time of the treatment. This sensitizing efficiency increased with decreasing polarity, i.e. in the order di-methyl ether, di-propyl ether, dibutyl ether and di-amyl ether. Haematoporphyrin di-amyl ether was more efficient than haematoporphyrin derivative and insignificantly less efficient than photofrin II (DHE). This was true for sensitization of both tumours and normal tissue.