Estramustine phosphate in prostate cancer. EORTC experience: preliminary results of Protocol 30762

Dysregulated ribonucleoprotein granules promote cardiomyopathy in RBM20 gene-edited pigs

Ribonucleoprotein (RNP) granules are biomolecular condensates-liquid-liquid phase-separated droplets that organize and manage messenger RNA metabolism, cell signaling, biopolymer assembly, biochemical reactions and stress granule responses to cellular adversity. Dysregulated RNP granules drive neuromuscular degenerative disease but have not previously been linked to heart failure. By exploring the molecular basis of congenital dilated cardiomyopathy (DCM) in genome-edited pigs homozygous for an RBM20 allele encoding the pathogenic R636S variant of human RNA-binding motif protein-20 (RBM20), we discovered that RNP granules accumulated abnormally in the sarcoplasm, and we confirmed this finding in myocardium and reprogrammed cardiomyocytes from patients with DCM carrying the R636S allele. Dysregulated sarcoplasmic RBM20 RNP granules displayed liquid-like material properties, docked at precisely spaced intervals along cytoskeletal elements, promoted phase partitioning of cardiac biomolecules and fused with stress granules. Our results link dysregulated RNP granules to myocardial cellular pathobiology and heart failure in gene-edited pigs and patients with DCM caused by RBM20 mutation.

Therapy Insight: parenteral estrogen treatment for prostate cancer—a new dawn for an old therapy

Oral estrogens were the treatment of choice for carcinoma of the prostate for over four decades, but were abandoned because of an excess of cardiovascular and thromboembolic toxicity. It is now recognized that most of this toxicity is related to the first pass portal circulation, which upregulates the hepatic metabolism of hormones, lipids and coagulation proteins. Most of this toxicity can be avoided by parenteral (intramuscular or transdermal) estrogen administration, which avoids hepatic enzyme induction. It also seems that a short-term but modest increase in cardiovascular morbidity (but not mortality) is compensated for by a long-term cardioprotective benefit, which accrues progressively as vascular remodeling develops over time. Parenteral estrogen therapy has the advantage of giving protection against the effects of andropause (similar to the female menopause), which are induced by conventional androgen suppression and include osteoporotic fracture, hot flashes, asthenia and cognitive dysfunction. In addition, parenteral estrogen therapy is significantly cheaper than contemporary endocrine therapy, with substantive economic implications for health providers.

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.

Necessity of re-evaluation of estramustine phosphate sodium (EMP) as a treatment option for first-line monotherapy in advanced prostate cancer

Estramustine phosphate sodium (EMP) was first introduced in the early 1970s for the treatment of prostate cancer, when EMP was supposed to have the dual effect of estrogenic activity and cytotoxicity. For the following decades, it was used mainly in hormone-refractory cases, with a conventional dosage of 4-9 capsules/day, which showed a 30-35% objective response rate. However, a very limited number of cases have been reported that used EMP as a first-line monotherapy in the conventional dosage. One study showed a response rate of 82%, which is at least as effective as conventional estrogen (diethylstilbestrol; DES) monotherapy. Nevertheless, EMP was almost abandoned for the treatment of prostate cancer because of severe adverse side-effects, especially in the cardiovascular system and gastrointestinal tract. Recently, two facts have become evident. First, EMP interferes with cellular microtubule dynamics but does not show alkylating effects. Second, EMP is able to produce a complex with calcium when dairy products are taken concomitantly with EMP, resulting in a decrease in the absorption rate of EMP from the gut. Many clinical trials have been undertaken without warning against concomitant dairy product intake since the introduction of EMP. This fact will jeopardize almost all the clinical trials performed before 1990. It is considered that response rates have been underestimated and better results could have been obtained because side-effects decrease dose-dependently. Low-dose EMP monotherapy (2 capsules/day) has been performed infrequently in previously untreated advanced prostate cancer. The only large trial by the European Organization for Research and Treatment of Cancer in 1984 was biased in selecting patients. Nevertheless, the response rate of EMP is comparable to that of DES. In this study, the adverse side-effects of EMP were less than that of DES. Recently, a study was conducted at the University of Tokyo of 11 patients with advanced prostate cancer on low-dose EMP as first-line monotherapy. The study found that the mean serum prostate-specific antigen level decreased to within the normal range by day 50; mean serum testosterone, leutinizing hormone and follicle-stimulating hormone reduced to undetectable levels by day 20; and mean serum estradiol increased to a very high level within 1 week. These data implicate that low-dose EMP can suppress quickly and adequately the pituitary-gonadal axis, although the antitumor effect has not as yet been elucidated. For these reasons, it is necessary to re-evaluate low-dose EMP monotherapy in previously untreated advanced prostate cancer.

Systemic management of prostate cancer

The objective of this review is to explore different therapeutic options for metastatic adenocarcinoma of the prostate. Orchiectomy, estrogen therapy, synthetic LHRH analogs and possibly antiandrogens are equally effective frontline treatment modalities. Ketoconazole is indicated in emergency situations, but chronic use is prevented by serious idiosyncratic toxicity and by long term complications. Combined androgen blockade (CAB), with leuprolide (or tryptorelin) and flutamide is more effective than single modality treatment in patients capable of strict treatment compliance. Estramustine phosphate may be as effective as CAB and may be the frontline treatment of choice in sexually active patients. Institution of single modality treatment may be delayed until cancer becomes symptomatic. Controversy lingers over whether the institution of CAB at an earlier time may improve progression free survival (PFS) and survival. Research projects of immediate clinical relevance include: comparison of CAB and estramustine; determination of the optimal time for CAB; study of other forms of CAB; and phase II trials of new cytotoxic agents.

Cardiovascular complications of estrogen therapy for nondisseminated prostatic carcinoma. A preliminary report from a randomized multicenter study

In a prospective multicenter study, 244 men with highly or moderately differentiated prostatic cancer in stage I, II or III (VACURG) were consecutively randomized to three groups of treatment: Group A (77 patients) received polyestradiol phosphate (Estradurin, Leo) 80 mg i.m. every fourth week + ethinyl estradiol (Etivex, Leo) 150 micrograms daily, group B (72 patients) estramustine phosphate (Estracyt, Leo) 280 mg twice daily, and group C (76 patients) no therapy. Only men without current or previous other malignancy and without cardiovascular disease were admitted to the study. After 4 1/2 years 125 of the 244 patients had left the study, 9 because of cancer progression (stage IV, VACURG). The most serious complications were cardiovascular, including ischemic heart disease, cardiac decompensation, cerebral ischemia and venous thromboembolism, which occurred in 24 patients from group A and 9 from group B as compared to only one patient in group C. The subgroup superficial or deep venous thrombosis comprised 11 group A and 2 group B patients. Estrogens (E + e) offered as palliative treatment to patients with non-generalized prostatic carcinoma is burdened with a high incidence of serious cardiovascular complications.