Oral estramustine and oral etoposide for hormone-refractory prostate cancer

Estramustine and etoposide have been shown to inhibit the growth of prostate cancer cells in experimental models. An in vivo synergism of the two agents, when administered to patients with metastatic prostate cancer refractory to hormone therapy, has been reported. To confirm these results, we administered this combination to a large number of patients with hormone-refractory prostate cancer (HRPC).

Fifty-six patients with metastatic HRPC were treated with oral estramustine 140 mg three times a day and oral etoposide 50 mg/m2/day for 21 days. Therapy was discontinued for 7 days and the cycle was then repeated. Therapy was continued until evidence of disease progression or unacceptable toxicity occurred. To control for the possible interference of an antiandrogen withdrawal effect, all patients discontinued antiandrogen therapy and were not enrolled in the study unless there was evidence of disease progression.

Forty-five percent of 33 patients with measurable soft tissue disease demonstrated an objective response, which included five complete and ten partial responses. Among 52 patients with osseous disease 17% showed improvement and 50% showed stability of bone scan. Thirty patients (58%) demonstrated a decrease of more than 50% in pretreatment prostate-specific antigen (PSA) levels. The median survival of all patients was 13 months. Good pretreatment performance status, measurable disease response, improvement or stability of bone scan, and PSA response were important predictors of longer survival.

We conclude that the combination of estramustine and etoposide is an active and well-tolerated oral regimen in HRPC.