Combination Chemotherapy Regimen Yields Impressive Results in Late-Stage Prostate Cancer
Atlanta, GA, May 17, 1999 -- The chemotherapeutic taxane agent docetaxel, combined with the nitrogen mustard estramustine phosphate and low dose hydrocortisone, appears to be a promising treatment for men with an advanced form of prostate cancer, according to the results of a phase II trial conducted by the Cancer and Leukemia Group B (CALGB) and presented at the annual meeting of the American Society of Clinical Oncology (ASCO).
The CALGB study, funded by the National Cancer Institute (NCI), found that the treatment was effective and well-tolerated in hormone-refractory prostate cancer. Hormone-refractory prostate cancer refers to advanced disease in which the patient no longer responds to conventional hormonal treatment with synthetic estrogen and antiandrogens. Almost all men whose cancers are initially sensitive or responsive to hormone therapy will eventually develop hormone resistance and tumor growth.
"When hormone therapy is no longer successful in men with prostate cancer, chemotherapy may be tried," Diane Savarese, MD, of the University of Massachusetts, said. "However, current drug therapy, particularly single-agent therapy, confers limited benefit, and the development of the new agents and combinations of agents may ultimately prove to be the most effective treatment once hormone resistance has emerged. Indeed, our data suggest that the docetaxel/estramustine combination may represent an encouraging approach."
The study included 47 men with an ECOG (Eastern Cooperative Oncology Group) performance status of 0 to 2 whose prostate cancer had progressed after initial hormone therapy. Patients who had undergone prior chemotherapy or who had a history of thrombotic events or severe cardiovascular disease were not eligible for enrollment.
Subjects received intravenous docetaxel, 70 mg/m2, given on the second day of every three-week cycle; oral estramustine, 10 mg/kg/d, administered in divided doses for five days; and oral low dose hydrocortisone (40 mg), given daily.
Overall, 40 patients were evaluable for response and/or toxicity. Of the 39 men with initially elevated PSA (prostate-specific antigen) levels, 27 (69%) had a greater than 50 percent decline in PSA. Of these 27 men, 21 had a greater than 75 percent decline. Twenty-one of 40 patients who received at least two cycles of therapy have measurable soft tissue disease. Of these patients, one had a complete response after six cycles, and three patients had a partial response in soft tissue. A complete response was defined as a complete disappearance of all clinical and X-ray signs of cancer, while a partial response refers to a 50 percent or greater decrease in measurable tumor size.
Side effects of the treatment included modest hematologic toxicity. Non-hematologic toxicity and gastrointestinal disturbances were infrequent. Based on the favorable results reported in this study, phase III studies should be undertaken to compare the combination regimen with other drugs that have been shown to be active in hormone-refractory prostate cancer including mitoxantrone and hydrocortisone, Dr. Savarese said.
During the past four decades, CALGB researchers have played a major role in improving the treatment of pediatric and adult leukemia, Hodgkin's disease, breast cancer and lung cancer. Future goals are to use the group's rapidly growing understanding of the biology of cancer to continue to develop better treatment and prevention strategies.