Relationship of prior hormonal therapy to subsequent estramustine phosphate treatment in advanced prostatic cancer

The relationship of prior hormonal therapy to subsequent response on estramustine phosphate (Estracyt) was examined in 107 patients with advanced prostatic cancer treated in two different Phase II chemotherapy trials. In both trials patients with the longest prior hormonal treatment were the least likely to respond to estramustine phosphate. Patients in the series from the National Prostatic Cancer Project with a response classification to prior hormonal therapy had only a 26 per cent response to subsequent estramustine phosphate therapy, whereas 40 per cent of those with no prior response to hormonal therapy responded to estramustine phosphate. This latter group had the shortest average disease duration from diagnosis. The sample of prostate cancers studied appeared to include groups that were sensitive to both hormones and cytotoxic activity as well as to either of these two alone. These data support the contention that estramustine phosphate may act both as an estrogenic and a cytotoxic agent.