Clinical trial of a new antigonadotropic substance, 2,6-cis-diphenylhexamethylcyclotetrasiloxane, in cancer of the prostate. A pilot study.

An organic siloxane compound, 2,6-cis-diphenylhexamethylcyclotetrasiloxane, (Cisobitan) has been shown to possess antigonadotropic properties. In this study it has been tried in prostatic cancer. 9 patients received the drug in the dose of 4-5 mg/kg body weight. General condition and subjective response, cytologic changes and semiquantitative scintigraphic changes of metastases were recorded, as well as common laboratory data. In this limited trial, Cisobitan was not adequate for tumour palliation. In a few instances subsequent oestrogen treatment was more effective. No side effects of Cisobitan were noted for periods up to 6 months. Further studies may be of value, perhaps using a higher dose.