Phase I trial of high-dose fosfestrol in hormone-refractory adenocarcinoma of the prostate

Outcomes and toxicity of oral Fosfestrol in metastatic castration-resistant prostate cancer-a real-world experience

Introduction

Although there are multiple drugs approved for the treatment of metastatic castration-resistant prostate cancer (CRPC), the cost can be a limiting factor in using them in a resource-limited setting. Therefore, less expensive alternatives are the need of the hour. We have been using Fosfestrol which is a cheap and orally administered oestrogen analogue in metastatic CRPC. We carried out a retrospective study to analyse its efficacy and toxicity.

Results

A total of 65 patients received Fosfestrol during 2015-2020. The median age was 65 years (range 50-83 years). Thirty-four patients (53%) had other medical comorbidities. Skeletal-only metastasis was the commonest pattern of metastasis (n = 41, 64%) followed by skeletal with nodal metastasis (n = 15, 23%). The majority of the patients had undergone upfront surgical castration (n = 60, 93%). All the patients had adenocarcinoma and 38 patients (58%) had a high Gleason's score. Forty-one patients (63%) had a prostate-specific antigen (PSA) response (decrease of ≥50% in the PSA concentration from the pre-treatment baseline PSA value) and 54 patients (83%) had a symptomatic response. At the end of a median follow-up of 16 months, the median progression-free survival (PFS) was 8.3 months (CI 4.7-11.8) and the median overall survival (OS) was 27.5 months (CI 25.4-29.5). PSA response and prior treatment with abiraterone acetate were found to have a significant association with survival outcomes. Patients with PSA response had better median PFS and OS; while patients who have received prior abiraterone acetate therapy had worse survival outcomes. Twenty-nine patients (45%) received some form of subsequent treatment after stopping Fosfestrol. The most common oxicity observed was thrombosis (n = 9, 13%) followed by gynecomastia (n = 4, 6%).

Conclusion

We conclude that oral Fosfestrol is a cheap and effective agent in the armamentarium against metastatic CRPC and warrants further studies in a clinical trial setting.

Diethylstilbestrol in castration-resistant prostate cancer

What's known on the subject? and What does the study add? Diethylstilbestrol (DES) was the first hormone treatment used for prostate cancer and has also shown effectiveness in castration-resistant disease in small studies; however, concerns over thromboembolic toxicity have restricted its use in the past. Over 200 elderly men with castration-resistant prostate cancer were treated with 1-3 mg of DES, given with 75 mg aspirin and breast bud irradiation. Almost 30% of men showed a significant PSA response and the median time to PSA progression was 4.6 months. Almost 20% of patients with pain had a significant analgesic benefit. The most important toxicity was thromboembolism in 10% of men. Overall the drug has an acceptable toxicity profile and offers a palliative benefit in frail elderly men who may not be fit for chemotherapy.

OBJECTIVE

• To assess the efficacy and toxicity of diethylstilbestrol (DES) in the management of castration-resistant prostate cancer (CRPC).

PATIENTS AND METHODS

• A total of 231 patients with CRPC received treatment with DES at the Royal Marsden Hospital between August 1992 and August 2000. • The median pre-treatment prostate-specific antigen (PSA) level was 221 ng/mL. • DES was used at a dose of 1-3 mg daily, with aspirin 75 mg. • The primary endpoint was PSA response rate.

RESULTS

• The PSA response rate (using PSA Working Group criteria) was 28.9%. • The median time to PSA progression was 4.6 months. • Of patients with bone pain, 18% had an improvement in their European Organisation for the Research and Treatment of Cancer pain score. • Thromboembolic complications were seen in 9.9% of all patients.

CONCLUSIONS

• DES has significant activity in CRPC and can be of palliative benefit. • DES has an acceptable toxicity profile in the management of patients with symptomatic CRPC when used at a dose of 1-3 mg, combined with aspirin and prophylactic breast bud radiotherapy.

Phase II Study of Low Dose and High Dose Conjugated Estrogen for Androgen Independent Prostate Cancer

PURPOSE

Although estrogens have known antitumor activity in androgen independent prostate cancer, the best studied agent, diethylstilbestrol, is no longer commercially available in the United States. We tested 2 doses of the conjugated estrogen Premarin(R) in patients with androgen independent prostate cancer to determine the efficacy and safety of this widely available medication.

MATERIALS AND METHODS

A total of 45 patients with progressive androgen independent prostate cancer were randomly assigned to receive Premarin 1.25 mg once (17) or 3 times (28) daily. Warfarin 1 mg daily was administered to all patients to minimize risk of thromboembolism. Low dose prophylactic breast irradiation was administered to most patients.

RESULTS

Of the patients receiving high dose Premarin 25% achieved a 50% or greater reduction in prostate specific antigen. No patients treated with low dose Premarin reached a 50% reduction in prostate specific antigen. After 3 months of treatment, 11 patients (39.3%) on the high dose arm and 6 patients (35.3%) on the low dose arm showed no signs of progression. Three patients (6.7%) had a thromboembolic event. No significant gynecomastia was noted. A significant difference in dehydroepiandrosterone sulfate levels was detected between those who did and did not respond to Premarin (p = 0.03).

CONCLUSIONS

High dose Premarin resulted in prostate specific antigen decreases of 50% or greater in 25% of patients with androgen independent prostate cancer. More than a third of patients receiving high or low dose Premarin maintained stable disease for at least 3 months. With concurrent warfarin 1 mg treatment, 6.7% experienced thromboembolic complications. Premarin 1.25 mg 3 times daily is a reasonable therapeutic option for patients with androgen independent disease.

Insulin-like growth factor binding protein-6 inhibits prostate cancer cell proliferation: implication for anticancer effect of diethylstilbestrol in hormone refractory prostate cancer

Diethylstilbestrol (DES) is a synthetic oestrogen, and its anticancer effects are exerted in androgen-dependent prostate cancer. The administration of DES decreases serum testosterone to castration levels. However, in androgen-independent prostate cancer patients, who are already orchiectomised, the administration of DES improves symptoms and decreases prostate-specific antigen (PSA). The mechanisms responsible for these direct inhibitory effects have been explained as biological actions not mediated by oestrogen receptors. We assessed the gene expression profiles of prostate cancer cells treated with DES, and investigated direct inhibitory effects of DES. DES inhibited the proliferation of LNCaP and PC-3 cells. cDNA microarray analysis showed that expression of many genes was downregulated by DES. However, insulin-like growth factor binding protein 6 (IGFBP-6) gene expression levels were upregulated in PC-3 cells. IGFBP-6 gene expression and protein levels significantly increased after DES treatment. Recombinant IGFBP-6 inhibited cell proliferation, and the inhibitory effect of DES was neutralised by anti-IGFBP-6 antibody. From the immunohistochemical analysis of IGFBP-6 using biopsy samples from androgen-independent prostate cancer, we found IGFBP-6 expression in androgen independent prostate cancer, and that DES treatment increased the IGFBP-6 staining intensity of the cancer cells in one sample. These findings suggested that DES induces IGFBP-6, which inhibits cell proliferation in an androgen-independent prostate cancer cell line, PC-3. IGFBP-6 therefore might be involved in the direct effects of DES in androgen-independent prostate cancer.

The evolving role of estrogen therapy in prostate cancer

Estrogens, including diethylstilbestrol (DES), were used as the primary medical treatment for metastatic prostate cancer for many years but have been superceded in the past two decades by luteinizing hormone-releasing hormone (LHRH) agonists, primarily because of the cardiovascular toxicity associated with oral estrogen therapy. Recently, a renewed interest in estrogen therapy for prostate cancer in the United States has developed as a result of 3 major issues. First, when measured by declines in prostate-specific antigen of > or = 50%, clinical trials have demonstrated activity of DES, DES-diphosphate, and the estrogenic herbal therapy PC-SPES in 21%-86% of patients treated in phase II trials of androgen-independent prostate cancer patients. Second, the recent description of estrogen receptor (ER)-b has led to a reevaluation of the role of estrogens in normal prostate development and cancer pathogenesis. In contrast to ER-a, ER-b is strongly expressed in normal prostate epithelium. Furthermore, loss of ER-b expression has been demonstrated in prostate cancers, suggesting a possible role for this pathway in the development of cancer. Finally, the issues of cost and safety of estrogens are being reassessed in the current environment of rising health care costs and improved cardiovascular care. In Europe, estrogen therapy is more accepted as a low-cost and effective alternative to LHRH agonists and antiandrogens. Toxicity of DES and other estrogens has also been attenuated by strategies that use lower doses and parenteral routes of administration, thereby avoiding hepatic first-pass metabolism and decreasing the risk of thromboembolism. Nonetheless, there remain many unanswered questions about the role of estrogen therapy in prostate cancer, including differences between specific drugs, optimal dose, timing, and patient selection. Further research is needed.

Use of PC-SPES, a commercially available supplement for prostate cancer, in a patient with hormone-naive disease

OBJECTIVES

PC-SPES, an over-the-counter supplement, is actually a combination of eight different herbs. It is being used by patients to treat cancer of the prostate at different stages of the disease and has been commercially available since November 1996. It has been observed to dramatically decrease prostate-specific antigen (PSA) values in several patients; however, its out-of-pocket cost ($162 to $486/mo) and potential side effects must be weighed against its potential objective benefits. We reviewed its use in 1 patient.

METHODS

A patient with clinically localized prostate cancer (T1c) with a PSA of 8.8 ng/mL, who decided to delay any conventional treatment, began treatment with 9 PC-SPES capsules/day.

RESULTS

After 3 weeks, his PSA dropped to 1.4 ng/mL and after a total of 8 weeks, his PSA was less than 0.1 ng/mL (undetectable). He has continued on a maintenance dose of 6 capsules per day, decreasing to 4 capsules per day, with a continuing undetectable PSA. During this time the patient also experienced a number of strong estrogenic effects: loss of libido, erectile dysfunction, extreme breast enlargement and tenderness, reduction in overall body hair, pitting edema, and a significant drop in his lipoprotein (a) level (from 46 to 11 mg/dL).

CONCLUSIONS

PC-SPES may provide additive advantages (or disadvantages) over prescribed hormonal treatments but must be compared with other hormonal and nonhormonal treatments in clinical trials with hormone-sensitive and -insensitive patients with prostate cancer to determine its future use or nonuse.

Clinical and biologic activity of an estrogenic herbal combination (PC-SPES) in prostate cancer

BACKGROUND

Herbal mixtures are popular alternatives to demonstrated therapies. PC-SPES, a commercially available combination of eight herbs, is used as a nonestrogenic treatment for cancer of the prostate. Since other herbal medicines have estrogenic effects in vitro, we tested the estrogenic activity of PC-SPES in yeast and mice and in men with prostate cancer.

METHODS

We measured the estrogenic activity of PC-SPES with transcriptional-activation assays in yeast and a biologic assay in mice. We assessed the clinical activity of PC-SPES in eight patients with hormone-sensitive prostate cancer by measuring serum prostate-specific antigen and testosterone concentrations during and after treatment.

RESULTS

In complementary yeast assays, a 1:200 dilution of an ethanol extract of PC-SPES had estrogenic activity similar to that of 1 nM estradiol, and in ovariectomized CD-1 mice, the herbal mixture increased uterine weights substantially. In six of six men with prostate cancer, PC-SPES decreased serum testosterone concentrations (P<0.05), and in eight of eight patients it decreased serum concentrations of prostate-specific antigen. All eight patients had breast tenderness and loss of libido, and one had venous thrombosis. High-performance liquid chromatography, gas chromatography, and mass spectrometry showed that PC-SPES contains estrogenic organic compounds that are distinct from diethylstilbestrol, estrone, and estradiol.

CONCLUSIONS

PC-SPES has potent estrogenic activity. The use of this unregulated mixture of herbs may confound the results of standard or experimental therapies and may produce clinically significant adverse effects.