[Brachytherapy of solid tumors. Use of chromic phosphate colloid]

With the purpose of studying the effectivity of an intratumoral single dose of chromic [32P] phosphate (Phosphocol) for the treatment of solid tumors, studies of bioelimination, biodistribution and therapeutic action were carried out in rats with experimental induced tumors. The results show that the percentage of total elimination is equal to 29.76 +/- 9.60% with a higher percentage in faeces 23.28 +/- 8.81% than in urine 6.48 +/- 2.11%. Biodistribution studies show that, 51.61 +/- 5.82% of the injected activity is found in the tumor while in organs with reticuloendothelial cells, the percentage of activity was 13.09 +/- 5.15% in liver and 2.88 +/- 1.23% in lung. On the other hand, when therapeutic action was evaluated, we found that the percentage of tumor regression (P.T.R) was 61.0% for the injected tumors. It is important to point out that 4 of the treated animals show bioelimination patterns in which the elimination rises suddenly at some time of the study. These results demonstrate that the use of this kind of colloids is not to be recommended for the treatment of solid tumors with moderated degree of vascularization, since its mobilization from the injection point may result in the consequent irradiation of different organs that are not under treatment.