This is the fifth completed randomized clinical trial of the National Prostatic Cancer Project. There were 125 patients with histologically confirmed relapsing clinical stage D prostatic cancer randomized to receive hydroxyurea, methyl-chloroethyl-cyclohexy-nitrosourea or cyclophosphamide. All patients had received and failed previous hormonal therapy. Patients whose disease progressed after 12 weeks on the initial therapy were crossed over or randomized to receive an alternate drug. There were 98 patients available for comparison of treatments. Objective responses included patients with complete or partial regression as well as stable disease. The response rates were 35 per cent for cyclophosphamide, 30 per cent for methyl-chloroethyl-cyclohexy-nitrosourea and 15 per cent for hydroxyurea. Subjective response parameters included improvement in performance status and relief of pain. Pain was improved in a fifth of the patients on each treatment area. Methyl-chloroethyl-cyclohexy-nitrosourea and hydroxyurea showed activity in advanced prostatic cancer patients but at the expense of excessive toxicity. Cyclophosphamide continues to be the most active single agent in this type of patient, particularly with regard to duration of response and survival. There was a statistically demonstrable advantage for cyclophosphamide over hydroxyurea and a marginal advantage over methyl-chloroethyl-cyclohexy-nitrosourea in survival experience.

There were 121 men with hormonally refractory metastatic cancer of the prostate who were randomized to receive estramustine phosphate or vincristine, or the combination of these 2 agents. All patients had received prior radiation therapy (greater than 2,000 rad). There were 90 patients who could be compared for response. The objective response rates (partial regression or stabilization of disease) for the 3 treatment groups were 26 per cent for estramustine phosphate, 24 per cent for estramustine phosphate plus vincristine and 15 per cent for vincristine. Subjective parameters varied little among the 3 regimens. The median duration of response for those responding to estramustine phosphate was similar (20 weeks) to that for vincristine (22 weeks) and greater than that for the combination (13 weeks). The probability of survival did not differ significantly for patients randomized to each of the 3 regimens. The addition of vincristine to estramustine phosphate did not enhance the response rate achieved by estramustine phosphate alone and vincristine alone produced the lowest response rate. Estramustine phosphate continues to be the most active agent in previously irradiated patients with hormonally refractory metastatic cancer of the prostate.

Results of the first nationally randomized trial of the National Prostatic Cancer Project revealed a demonstrable advantage for chemotherapy in the management of advanced disease (Stage D in relapse from endocrine therapy). Both cyclophosphamide and 5-Fluorouracil showed improved activity over standard therapy. A second trial for patients previously irradiated, with less tolerance to myelosuppressive agents, revealed an advantage for estramustine phosphate and streptozotocin over standard therapy. Subsequently completed trials have revealed activity for prednimustine and imidazole carboxamide (DTIC). Trials currently underway for newly-diagnosed Stage D and for Stage D disease clinically stable to diethylstilbestrol (DES) show promising activity for DES combined with cyclophosphamide. Current trials with single agents in advanced disease are comparing methyl-CCNU and hydroxyurea with cyclophosphamide; another is evaluating estramustine phosphate and vincristine alone and in combination. The use of chemotherapy in earlier staged patients as adjuvants to definitive surgery or irradiation is underway in two clinical trials, where the effect of cyclophosphamide and estramustine phosphate as long-term therapies is compared with no additional treatment.

In this third cooperative chemotherapy trial of the National Prostatic Cancer Project 165 patients with histologically confirmed, relapsing clinical stage D prostatic cancer were randomized to receive either imidazole-carboxamide, procarbazine or cyclophosphamide. All patients had received and failed previous hormonal therapy. Patients whose disease progressed after 12 weeks on initial therapy were crossed over or randomized to receive an alternate drug. There were 129 patients available for comparison of treatments. The objective response rates (partial regression plus stable disease) were 26% for cyclophosphamide, 27% for imidazole-carboxamide and 14% for procarbazine. Subjective responses were noted in pain relief, improvement in performance status and weight gain. Procarbazine was associated with excessive toxicity, resulting in many patients (28%) discontinuing therapy within the first 3 weeks and closure of this particular arm of the study. The regimen of initial imidazole-carboxamide therapy with a later cross-over to cyclophosphamide when the disease continues to progress is associated with the longest increase in survival. Imidazole-carboxamide and cyclophosphamide appear to be active agents in advanced prostatic cancer and are worthy of continued use in this disease.

The alkaline phosphatase isoenzymes in 105 patients with stage D carcinoma of the prostate who entered the National Prostatic Cancer Study were analyzed and these values were correlated to clinical response. Only patients with at least 3 measurements of alkaline phosphatase were evaluated. In 91% of patients with metastatic bone disease, bone alkaline phosphatase was elevated. Those patients with higher pre-treatment levels of alkaline phosphatase generally showed a poorer response to therapy. The results of alkaline phosphatase isoenzyme estimation indicate that these biological markers may be used in the evaluation of patients with metastatic prostatic cancer to predict and monitor their response to chemotherapy. The evaluation of bone and liver alkaline phosphatase isoenzymes in earlier stages also may be valuable.

An immunochemical method for detection of prostatic acid prosphatase is described. Purified acid phosphatase was isolated from cancerous human prostate. A specific antiserum to the purified enzyme was produced in rabbits. The antiserum to postatic acid phosphatase did not react with acid phosphatase originating from other tissues. A counter immunolectrophoresis, utilizing the specific antibodies and a chemical staining technique, has been developed and clinically evaluated. Sera from patients with prostatic carcinoma (6/20 of stage B, 27/49 of stage C, and 98/125 of stage D) gave positive results. Sera from 19 patients with benign prostatic hypertrophy, from 89 patients with other tumors, from 12 patients with Gaucher's disease, from 107 healthy volunteers, and from 50 normal age-matched men all gave negative results. The sensitivity of this method was 0.4 IU of enzyme activity or 20 ng per ml of prostatic acid phosphatase protein. Further clinical evaluation of patients in the early stage of prostatic cancer and of patients undergoing chemotherapy is in progress.

Estramustine has been shown previously to be an effective drug in the treatment of metastatic prostatic cancer, demonstrating significant objective and subjective responses in long-term non-randomized trials and in other randomized trials. In this study prednimustine alone has shown a minimal over-all objective response rate of 12.9 percent of the cases, although with marked subjective improvement of pain relief and patient performance status. The combination of prednimustine with estramustine did not result in improvement of objective or subjective response parameters. The effects in terms of responses or in terms of toxicity for either agent were not additive when they were given in combination. Cross-over for those patients whose disease progressed on prednimustine therapy to estramustine had some benefit in over-all survival. Prednimustine alone or in combination with estramustine may be used safely and could improve markedly the quality of life for irradiated patients with advanced prostatic cancer who failed on hormonal treatment and have too poor a bone marrow reserve to be treated by other currently available myelosuppressive agents.

In the 36 months since its inception, the National Prostatic Cancer Project treatment subgroup has randomly assigned over 360 patients with progressive advanced prostatic cancer who were no longer responsive to endocrine manipulation to either one of four different clinical studies. The initial study demonstrated a clear superiority for 5-fluorouracil (5-FU) and cyclophosphamide over continued conventional therapy. Beneficial responses were documented and are associated with increased survival rates and relief from pain and other symptoms. A proportionately larger number of patients obtained clinical benefit (stable and partial regression) on cyclophosphamide than on standard or 5-FU therapy. The criteria for evaluation of patients are supported by the survival data, ie, responders have survived for a longer period of time than those patients who continued in progression. Preliminary data from the subsequent protocols have documented a 30% response (stable and partial regression) in patients receiving oral estramustine phosphate and definite responses in patients treated with DTIC; Too few patients have been treated with Leo 1031 to offer total response rates at this time, although the early results are promising. These clinical studies have firmly established a place for chemotherapy in the management of prostatic cancer. New trials will introduce single- and multiple-drug chemotherapy at earlier phases of the clinical course of prostatic cancer patients.

In this second nationally randomized cooperative chemotherapy trial of the National Prostatic Cancer Project 125 patients with histologically confirmed progressing advanced carcinoma of the prostate (clinical stage D) who had had prior pelvic irradiation of at least 2,000R received as initial therapy 1 of 2 non-myelosuppressive agents—estramustine phosphate or streptozotocin—for comparison with patients randomized to receive standard treatment. Patients whose disease was progressive after 12 weeks on chemotherapy were crossed over to receive the alternate therapeutic agent. Response to treatment was evaluated in 105 patients on the basis of previously established and defined criteria.

The response and duration of survival were evaluated for patients with stage D relapsing prostatic cancer whowere randomized to cyclophosphamide (cytoxan), 5-fluorouracil (5-FU) or standard therapy, or to subsequent chemotherapies. The chemotherapies on Initial randomization were superior to the standard therapy In the number of responders and duration of response. Survival was longer for responders (stable or partial regression) on chemotherapy by comparison to responders (stable only) on standard therapy. The survival for patients receiving Initialand crossover chemotherapy was significantly improved for patients who responded to therapy. Chemotherapy of advanced relapsing stage D prostatic cancer Is more beneficially treated by specific chemotherapy as shown in this randomized study.

The National Prostatic Cancer Project has randomized this study for endocrine-resistant prostatic cancer patients for treatment with standard hormonal or other therapies compared to 5-fluorouracil and cyclophosphamide. Both agents were found at the probability level of 0.05 to have a significant advantage over standard treatment in terms of objective response, subjective improvement and minimal toxicity. Additional chemotherapy protocols are currently under way. This randomized trial is the first report of such a national study completed to date. We are much encouraged by this program and believe that additional agents now under consideration will provide additionally encouraging results.