Relative effectiveness of alternative androgen withdrawal therapies in initiating regression of rat prostate

Intermittent androgen suppression in the treatment of prostate cancer: a preliminary report

OBJECTIVES

To test the feasibility of using intermittent androgen suppression in the treatment of prostate cancer by taking advantage of the reversible action of medical castration.

METHODS

Observations were made on a group of 47 patients (clinical Stage D2, 14; D1, 10; C, 19; B2, 2; and A2, 2) with a mean follow-up time of 125 weeks. Treatment was initiated with combined androgen blockade and continued for at least 6 months until a serum prostate-specific antigen (PSA) nadir was observed. Medication was then withheld until the serum PSA increased to a mean value between 10 and 20 ng/mL. This cycle of treatment and no treatment was repeated until the regulation of serum PSA became androgen independent.

RESULTS

The first two treatment cycles lasted 73 and 75 weeks, with a mean time off therapy of 30 and 33 weeks and an overall mean percentage time off therapy of 41% and 45%, respectively. The mean time to achieve a nadir level of serum PSA was 20 weeks in cycle 1 and 18 weeks in cycle 2. Serum testosterone returned to the normal range within 8 weeks (range, 1 to 26) of stopping treatment. The off-treatment period in both cycles was associated with an improvement in sense of well-being and the recovery of libido and potency in the men who reported normal or near-normal sexual function before the start of therapy. In 7 patients with Stage D2 disease, the cancer progressed to an androgen-independent state. The mean and median times to progression were 128 weeks and 108 weeks, respectively. Seven patients have died, 1 from a noncancer-related illness, with mean and median overall survival times of 210 weeks and 166 weeks, respectively.

CONCLUSIONS

Prostate cancer is amenable to control by intermittent androgen suppression. This approach affords an improved quality of life when the patient is off therapy. It also results in reduced toxicity and cost of treatment and possibly delays tumor progression. Whether survival is affected in a beneficial or adverse way remains to be studied in a randomized, prospective study.

The effect of active immunization against gonadotropin-releasing hormone on the ultrastructure of the rat ventral prostate

To evaluate the effects of active immunization against gonadotropin-releasing hormone (GnRH) on the ultrastructure of the rat ventral prostate, male Sprague-Dawley rats received three consecutive intramuscular injections of 10 micrograms/100 g body weight (D-Lys6)-GnRH-diphtheria toxoid conjugate (GnRH-DT vaccine). Following immunization, test animals developed sufficiently high antibody titres to block the pituitary gonadal axis. Consequently testosterone values dropped to the levels in castrates. This therapy leads to atrophy of the prostate. Following immunization a strong immunological response, indicating the presence of considerable amounts of a GnRH-like peptide, was observed in the ventral prostates as early as 14 days after the first injection of GnRH-DT. Immunoneutralisation of GnRH-like activity may contribute to the effects observed.

Luteinizing hormone-releasing hormone agonists in prostate cancer. Elimination of flare reaction by pretreatment with cyproterone acetate and low-dose diethylstilbestrol

BACKGROUND

In response to the first administration of a luteinizing hormone-releasing hormone (LHRH) agonist, the secretion of pituitary gonadotropin increases sharply and gives rise to a transient surge in the concentration of serum testosterone. This effect reaches a peak 4 to 7 days after the start of therapy and results in the onset of clinical symptoms and signs of tumor flare in 5% to 10% of patients.

METHODS

To determine whether the effects of the LHRH-induced flare reaction are preventable, cyproterone acetate (100 mg) and low-dose diethylstilbestrol (0.1 mg) were administered daily for 4 weeks to inhibit the pituitary before the initiation of therapy with a depot LHRH agonist, goserelin acetate (3.6 mg every 4 weeks). Diethylstilbestrol was stopped after 8 weeks to eliminate associated minor toxicity while administration of cyproterone acetate was continued to suppress vasomotor symptoms. Twenty-four men with histologically confirmed prostate cancer were enrolled in the study: 6 with Stage C, 2 with Stage D1, and 16 with Stage D2 disease.

RESULTS

Lead-in therapy reduced the concentration of serum testosterone into the castrate range within 1 week, and no significant change was observed in the mean level after administration of goserelin acetate. Neither was there an effect on the initial rate of normalization of serum prostate specific antigen (PSA); normal PSA values were obtained in 50% of patients after 10 weeks and in 70% after 32 weeks. In the subgroup of patients with Stage D2 disease, longer median survival was predicted by a normal serum PSA, either stable or decreasing, after 32 weeks of treatment. The regimen was well tolerated with a low incidence of hot flushes.

CONCLUSIONS

These results imply that in the absence of LHRH-induced tumor flare, prognosis is related to the ability of therapy to maintain a PSA nadir in the normal range.

Evaluation of Win 49,596, a novel steroidal androgen receptor antagonist, in animal models of prostate cancer

A series of experiments were conducted to evaluate the effects of Win 49,596, a novel steroidal androgen receptor antagonist, in animal models of prostate cancer. In the first experiment, oral administration of Win 49,596 at doses of 30, 100, or 300 mg/kg/day for 28 days inhibited (P less than 0.05) the growth of the androgen-sensitive PAP variant of the Dunning R-3327 prostatic carcinoma in intact male rats relative to intact controls. The degree of inhibition at 100 and 300 mg/kg/day Win 49,596 was similar (P greater than 0.10) to that observed in castrate controls as well as in intact rats administered the nonsteroidal androgen receptor antagonist flutamide orally at 15 mg/kg/day. Castration as well as treatment with either Win 49,596 or flutamide also decreased (P less than 0.05) the weight of the prostate in tumor-bearing animals. Additional studies were conducted to determine the effect of Win 49,596 on the growth of the androgen-dependent PC-82 human prostatic carcinoma xenografted into athymic nude male mice. Oral administration of Win 49,596 at 30, 100, or 300 mg/kg/day for 35 days inhibited (P less than 0.05) tumor growth relative to intact controls. The degree of tumor inhibition was similar to that observed in intact male mice administered the nonsteroidal androgen receptor antagonist flutamide orally at 30 mg/kg/day but was less than that observed following castration. Ventral prostate weights were also reduced (P less than 0.05) in castrate mice as well as in intact mice administered either Win 49,596 or flutamide. In the last experiment, at equivalent total daily dosages of either 150 or 300 mg/kg/day Win 49,596, twice a day (BID) dosing was more effective than once a day (SID) dosing in inhibiting tumor growth. The inhibitory effects of Win 49,596 at 150 mg/kg BID on tumor growth were similar to those observed following castration. Although Win 49,596 treatment reduced (P less than 0.05) ventral prostate weights relative to intact controls, there was no difference (P greater than 0.10) between SID vs. BID dosing. Based on the results of these studies and subject to further testing, Win 49,596 may have utility in the treatment of hormonally dependent metastatic prostate cancer in humans.

The combination of cyproterone acetate and low dose diethylstilbestrol in the treatment of advanced prostatic carcinoma

Cyproterone acetate is a steroidal antiandrogen with weak progestational activity that results in the partial suppression of pituitary gonadotropin. We demonstrate that the associated decrease in serum testosterone is more complete and prolonged if cyproterone acetate (200 mg. daily) is combined with a low dose of diethylstilbestrol (0.1 mg. daily). The effectiveness of the combination in the treatment of prostatic carcinoma was investigated in 51 patients with stage D2 malignancy. From an initial concentration of 360 +/- 23 ng. per dl. (mean +/- standard error), serum testosterone decreased to 56 +/- 5 ng. per dl. after 1 week and reached a plateau of approximately 30 ng. per dl. after 2 months. This was accompanied by a decrease in serum prostatic acid phosphatase from a mean starting concentration of 43 +/- 11 ng. per ml. to a low of 3 +/- 1 ng. per ml. at 12 months; the proportion of normal values increased from 10 to 80 per cent. A complete response was observed in 7 patients (13 per cent), partial response in 35 (69 per cent) and stable disease in 8 (16 per cent), yielding an over-all objective response rate of 98 per cent (1980 National Prostatic Cancer Project criteria). The actuarial median time to progression was 17 months and the median survival time was 23.5 months. In 26 patients who subsequently had signs of progressive carcinoma the relapse rate in bone (85 per cent) far exceeded that in nonskeletal sites (23 per cent). The incidence of cardiovascular toxicity was 12 per cent. These results indicate that cyproterone acetate and low dose diethylstilbestrol may be co-administered to achieve a synergistic and potent androgen withdrawal effect in the treatment of advanced prostatic carcinoma.