Prolactin and pituitary gonadotropin values and responses to acute luteinizing hormone-releasing hormone (LHRH) challenge in patients having long-term treatment with a depot LHRH analogue

A review of clinical evidence to assess differences in efficacy and safety of luteinizing hormone-releasing hormone (LHRH) agonist (goserelin) and LHRH antagonist (degarelix)

Luteinizing hormone-releasing hormone agonist (LHRH-A), goserelin, and antagonist, degarelix, are both indicated for the treatment of advanced prostate cancer (PCa); however, large comparative trials evaluating their efficacy and safety are lacking. In this review, we assessed the available evidence for both the drugs. Although degarelix achieves an early rapid decline in testosterone (T) and prostate-specific antigen (PSA) levels, median T and PSA levels, in addition to prostate volume and International Prostate Symptom Scores, become comparable with goserelin over the remaining treatment period. Degarelix causes no initial flare, therefore it is recommended in patients with spinal metastases or ureteric obstruction. Goserelin achieves lower PSA, improved time to progression, and better survival outcomes when administered adjunctively to radiotherapy compared with radiotherapy alone, with significant results even over long-term follow-up. The evidence supporting adjuvant degarelix use is limited. Goserelin has better injection site safety, single-step delivery, and an efficient administration schedule compared with degarelix, which has significantly higher injection site reactions and less efficient administration mechanism. There is conflicting evidence about the risk of cardiovascular disease (CVD), and caution is required when using LHRH-A in patients with preexisting CVD. There is considerable long-term evidence for goserelin in patients with advanced PCa, with degarelix being a more recent option. The available comparative evidence of goserelin versus degarelix has several inherent limitations related to study design, sample size, conduct, and statistical analyses, and hence warrants robust prospective trials and long-term follow-up.

Efficacy and safety of degarelix in patients with prostate cancer: Results from a phase III study in China

Objective

To establish non-inferiority of gonadotropin-releasing hormone degarelix compared with goserelin in suppressing and maintaining castrate testosterone levels from Day 28 to Day 364 in Chinese patients with prostate cancer.

Methods

This is an open-label, multi-centre study in which men aged ≥18 years were randomised in a 1:1 ratio to once-a-month subcutaneous injection of either degarelix (240/80 mg) or goserelin (3.6 mg) for 12 months. The primary endpoint was difference in 1-year cumulative probability of suppressing testosterone to ≤0.5 ng/mL. Non-inferiority was to be established if the lower 95% confidence interval (CI) limit for difference in cumulative probability between the treatment arms was greater than −10%. Secondary endpoints included cumulative probability of prostate-specific-antigen-progression-free-survival (PSA-PFS). Safety was also assessed.

Results

Baseline demographics and disease characteristics were similar between degarelix (n=142) and goserelin (n=141) treatment arms. The difference in cumulative probability of maintaining castrate levels from Day 28–364 was 3.6% (95% CI:−1.5%, 8.7%), demonstrating non-inferiority of degarelix. The cumulative probability of PSA-PFS at Day 364 was higher for degarelix (82.3%, 95% CI: 74.7%, 87.7%) versus goserelin (71.7%, 95% CI: 63.2%, 78.5%, p=0.038). Adverse events (AEs) were similar between treatment arms, except for more injection site reactions with degarelix versus goserelin. Four (2.8%) and nine (6.4%) patients discontinued due to AEs in degarelix and goserelin groups, respectively.

Conclusion

Degarelix was non-inferior to goserelin in achieving and maintaining testosterone suppression at castrate levels during 1-year treatment. PSA-PFS was significantly higher with degarelix, suggesting improved disease control. Both treatments were well tolerated.

New considerations for ADT in advanced prostate cancer and the emerging role of GnRH antagonists

Androgen deprivation therapy (ADT) is first-line treatment for metastatic prostate cancer (PCa). Gonadotrophin-releasing hormone (GnRH) agonists are the most commonly used ADT but have several theoretical physiologic disadvantages (e.g. initial testosterone surge, potential microsurges upon repeat administration). Testosterone surge delays the intended serologic endpoint of testosterone suppression and may exacerbate clinical symptoms. GnRH antagonists were developed with a view toward overcoming these potential adverse physiologic events. This review evaluates GnRH agonists and antagonists, assessing the potential future role of antagonists in PCa and strategies to minimize ADT adverse events (AEs). Evidence was identified via PubMed search (by GnRH agent and other ADT-related terms), from review article bibliographies, and authors' therapy area knowledge, with articles included by author consensus. Degarelix shows similar efficacy to a GnRH agonist in achieving and maintaining castration, with faster onset and without testosterone surge/microsurges. Phase III data showed that, in the first treatment year, degarelix displayed a lower risk of PSA failure or death (composite endpoint), lower levels of the bone marker serum alkaline phosphatase (in baseline metastatic disease), and fewer musculoskeletal AEs than the agonist leuprolide. Also, crossing over from leuprolide to degarelix after 1 year reduced the risk of PSA failure or death. ADT displays an AE spectrum which can impact quality of life as well as causing significant morbidities. Strategies to improve ADT tolerability have become increasingly important including: a holistic management approach, improved diet and exercise, more specific monitoring to detect and prevent testosterone depletion toxicities, and intermittent ADT allowing hormonal recovery between treatment periods. Clinical studies suggest possible benefits of GnRH antagonists over agonists based on different mechanisms of action. GnRH antagonists should now be considered as an alternative first-line ADT option in advanced PCa. Intermittent ADT and a holistic treatment approach are promising strategies to improve ADT tolerability.

Luteinising hormone-releasing hormone antagonists in prostate cancer therapy

The introduction of androgen blockade therapy using luteinising hormone-releasing hormone (LHRH)/gonadotropin-releasing hormone analogues alone or in combination with non-steroidal antiandrogens has a major impact in both survival and quality of life of patients with locally advanced and metastatic prostate cancer. The effect of LHRH agonists is based on the continuous binding to the LHRH receptor (LHRH-R) on the gonadotrope cells of the pituitary, which although initially stimulate LH release, consequently downregulates the LHRH-R, thereby suppressing serum LH, testosterone levels and 5alpha-dihydrotestosterone levels. Because this initial surge of LH and testosterone can cause adverse consequences in these patients (the so-called flare-up symptoms), immediate inhibition of LH release and testosterone production is desirable and this can be achieved with the use of the LHRH antagonists. In addition, there exist data to support a direct anticancer effect of LHRH antagonists on prostate cancer cells. This review summarises the potential clinical use of the LHRH antagonists in prostate cancer patients.

Pharmacotherapy for prostate cancer, with emphasis on hormonal treatments

For more than half a century, hormonal therapy has been one of the cornerstones of prostate cancer therapy. However, the position and timing of androgen deprivation therapy is continuously challenged. Nowadays, it is often combined with other types of treatment in a multi-modal approach, especially with radiation therapy. Besides the well-known luteinising hormone-releasing hormone agonists, several developments have been introduced (e.g., luteinising hormone-releasing hormone antagonists or improved depot formulations achieving a better pharmacokinetic slope and lower testosterone levels). Research developments include a better understanding of the different gonadotropin-releasing hormone isoforms, the ligand-independent transformation of the androgen receptor and androgen receptor overexpression in hormone-insensitive disease. Prostate cancer, previously thought to be chemotherapy insensitive, is now treated at the metastatic stage by taxane-based chemotherapies. The combination of hormonal therapy and chemotherapy is currently studied at various stages of the disease, as early as localised or locally advanced prostate cancer. It is very likely that, in the future, pharmacological treatment for prostate cancer will include combination therapies rather than monotherapies. The authors suggest an in-depth re-evaluation of the place of androgen deprivation therapy in prostate cancer.

Abarelix for injectable suspension: first-in-class gonadotropin-releasing hormone antagonist for prostate cancer

Abarelix, a gonadotropin-releasing hormone antagonist, with its indication for advanced symptomatic prostate cancer, represents the newest category of hormonal therapy introduced in the past 15 years. Results from Phase II and III clinical trials demonstrate the advantages of abarelix over commonly used luteinizing hormone-releasing hormone (LHRH) agonist therapy: abarelix does not cause a surge in serum testosterone that can precipitate a flare phenomenon or worsening of disease, particularly dangerous for patients with metastatic, symptomatic disease, and produces medical castration more quickly. Abarelix was also demonstrated to promptly and substantially reduce follicle-stimulating hormone levels to lower than LHRH agonist. Study results demonstrate effective anticancer responses during extended exposure to abarelix: improvements in pain score and/or analgesic use, improvements in urinary symptoms (including urinary catheter removal) and complete avoidance of bilateral orchiectomy for patients undergoing at least 12 weeks of treatment. In Phase III clinical trials, abarelix demonstrated a similar overall safety profile when compared with LHRH agonist monotherapy, and a superior safety profile when compared with LHRH agonist plus antiandrogen combination therapy. Abarelix patients experienced a greater incidence of immediate-onset systemic allergic reactions as compared with control arms.

Dose-escalated abarelix in androgen-independent prostate cancer: a phase I study

Follicle-stimulating hormone has been shown to be a mitogen in preclinical models of androgen-independent prostate cancer and abarelix has been previously shown to significantly reduce follicle-stimulating hormone levels in patients when administered monthly. Consequently, we evaluated the safety of more frequent (biweekly) dosing of abarelix and characterized the effect of this dosing schedule on serum follicle-stimulating hormone levels in men with prostate cancer that is progressing despite luteinizing hormone-releasing hormone agonist therapy. Twenty-one patients with prostate cancer progressing on gonadotropin-releasing hormone agonist therapy discontinued the gonadotropin-releasing hormone agonist and received abarelix-depot 100 mg by intramuscular injection every 2 weeks for up to 12 weeks. Safety profile and effect on serum follicle-stimulating hormone were the primary end-points, while prostate-specific antigen response was a secondary end-point. Abarelix therapy was generally well tolerated. One patient experienced an acute immediate allergic reaction. The mean follicle-stimulating hormone serum concentration declined from 3.5 mIU/ml (95% confidence interval: 2.7-4.3) to 2.0 mIU/ml (95% confidence interval: 1.3-2.6) on day 57 and to 2.0 mIU/ml (95% confidence interval: 0.9-3.0) on day 85 (P=0.008 in a Kruskal-Wallis test), but no patient's follicle-stimulating hormone has reached the lower limit of quantitation (below 0.15 mIU/ml). No patient met criteria for prostate-specific antigen response. At the end of 12 weeks of therapy, three (14.3%) patients had no change in prostate-specific antigen levels on days 57 and 85 compared with baseline. Twelve patients (57%) had stable disease throughout treatment defined as percent change from baseline within -50 to 50% at a given time-point confirmed by a second measurement at least 4 weeks later. Treatment with biweekly abarelix in patients with androgen-independent prostate cancer is feasible with no unexpected toxicity, but fails to completely suppress serum follicle-stimulating hormone levels or produce prostate-specific antigen responses.

Abarelix: the first gonadotrophin-releasing hormone antagonist for the treatment of prostate cancer

The high incidence of prostate cancer makes it a major healthcare problem and the second leading cancer-related cause of death among men in developed countries. The hormonal treatment of prostate cancer is indicated for the palliation of symptomatic and metastatic disease in older patients, and as neoadjuvant treatment of different modalities of radiotherapy. This hormonal treatment is based on the study conducted by Huggins in 1940 and consists of androgen suppression. Since the clinical availability of the first luteinising hormone-releasing hormone (LHRH) agonist, no significant improvement has been made in the field of medical castration. Taking these data into consideration, the recent approval of abarelix by the FDA, the first gonadotrophin-releasing hormone (GnRH) antagonist, appears to be promising news. The pharmacology of the molecule and the clinical studies that led to FDA approval will be reviewed. The place of GnRH antagonists in the treatment modalities of prostate cancer will then be discussed.

Hormone therapy in prostate cancer: LHRH antagonists versus LHRH analogues

GnRH agonists have a proven and well-established role in the management of prostate cancer. Further adaptations of the amino-acid sequence led to the development of antagonists with potential therapeutic uses, including a possible role in prostate cancer patients. Treatment of prostate cancer with GnRH agonists results in an initial flare of symptoms that may be prevented by co-administration of a steroidal or non-steroidal antiandrogen. However, this can be associated with additional adverse effects. Clinical studies have shown that GnRH antagonists produce a rapid decline in testosterone but without the disease flare. However these short-term effects have yet to be proven to lead to long-term survival benefits. There have been some reports that antagonists may be associated with adverse effects due to histamine release leading to severe allergic reactions. GnRH agonists are currently available in a range of depot formulations, allowing treatment to be tailored to the patient's needs. At present, the antagonists are only available as on-month depot formulations, which may limit their clinical use. Abarelix should be given intramuscularly. It is the first GnRH antagonist which is approved by the FDA for patients with advanced prostate cancer who should be treated under a risk management program. In Europe, abarelix has not been registered yet.

Targeting FSH in androgen-independent prostate cancer: abarelix for prostate cancer progressing after orchiectomy

OBJECTIVES

To determine the efficacy of the gonadotropin-releasing hormone antagonist abarelix in patients with androgen-independent prostate cancer progressing after orchiectomy and to measure its effect on serum follicle-stimulating hormone (FSH).

METHODS

Sixteen patients with prostate cancer progressing after orchiectomy received abarelix-depot 100 mg by intramuscular injection on days 1, 15, and 29 and then every 28 days for up to 24 weeks (52 weeks in patients who met the criteria for a prostate-specific antigen [PSA] response after 24 weeks). PSA response was the primary endpoint and was defined as a 50% reduction confirmed 4 weeks later. The time to progression and effect of therapy on serum FSH were secondary endpoints.

RESULTS

No patient met the criteria for a PSA response. Five patients (31%, 95% confidence interval 11% to 58%) experienced confirmed reductions in the PSA level ranging from 9.3% to 31.8%. At the end of the six cycles of therapy, 6 patients remained stable without PSA progression or other signs of disease progression. The median time to progression was 12 weeks (95% confidence interval 6 to 18). The mean serum FSH concentration declined after 4 weeks of study treatment by nearly 90% from a baseline of 45.1 IU/L (95% confidence interval 34.0 to 56.2) and remained suppressed throughout the observation period. Treatment was well tolerated, with one grade 3 allergic reaction.

CONCLUSIONS

Treatment with abarelix in patients with androgen-independent prostate cancer after orchiectomy results in marked reduction in circulating FSH. None of the patients met the PSA response criteria; nonetheless, minor reductions in serum PSA were observed in 5 of 16 patients.

Adjuvant goserelin improves clinical disease-free survival and reduces disease-related mortality in patients with locally advanced or localized prostate cancer

This article reviews the clinical disease-free survival (DFS) and disease-related mortality (DRM) data from published prospective, randomized trials of goserelin, given alone as adjuvant treatment or combined with a nonsteroidal antiandrogen as neoadjuvant treatment in patients with locally advanced or localized prostate cancer. Four trials were of radiotherapy and one of radical prostatectomy. The five trials included > 3500 patients and the median follow-up was 4.8-7.1 years. There were statistically significant improvements in clinical DFS with goserelin support relative to the control treatment in all five trials (each log-rank P </= 0.004). Reductions in the risk of DRM were statistically significant with adjuvant goserelin vs no adjuvant treatment to support radiotherapy in one trial, and with adjuvant goserelin or bilateral orchidectomy vs no adjuvant treatment to support radical prostatectomy in another (each log-rank P </= 0.001). Time-point estimates of the rates of clinical DFS and DRM were in favour of goserelin support vs control in all five trials at 5 years and in the three trials for which data were available at 8 years. Goserelin support therefore improves clinical DFS and reduces DRM after radiotherapy or radical prostatectomy. Adjuvant goserelin may offer greater clinical benefits than neoadjuvant hormonal treatment.

Phase II study of abarelix depot for androgen independent prostate cancer progression during gonadotropin-releasing hormone agonist therapy

PURPOSE

We determine the clinical efficacy of the gonadotropin-releasing hormone (Gn-RH) antagonist abarelix in patients with androgen independent prostate cancer, and measure its effect on serum follicle-stimulating hormone (FSH) and testosterone.

MATERIALS AND METHODS

A total of 20 patients with prostate cancer progression during Gn-RH agonist therapy received 100 mg. abarelix depot by intramuscular injection on days 1, 15 and 29, and then every 28 days for up to 24 weeks. Gn-RH agonist therapy was not continued. Patients who met criteria for prostate specific antigen (PSA) response after 24 weeks of therapy could receive treatment for up to 52 weeks. PSA response was the primary end point and was defined as a 50% decrease confirmed 4 weeks later. Secondary end points of this study were the effect of therapy on serum FSH and testosterone.

RESULTS

No patient met the criteria for PSA response. At the end of the 6 cycles of therapy 2 patients remained stable without PSA progression or other signs of disease progression. Median time to progression was 8 weeks (95% CI 5.7-10.3). Mean serum FSH decreased by more than 50% from a baseline of 5.7 IU/l. (95% CI 4.2-7.1) and remained suppressed throughout the observation period. Mean serum testosterone did not change after 4 and 8 weeks of therapy and remained in the anorchid range. Treatment was well tolerated with no grade 3 or higher toxicity.

CONCLUSIONS

Treatment of androgen independent prostate cancer with abarelix decreases circulating FSH and maintains anorchid testosterone but does not result in clinical responses.

Effects on the endocrine system of long-term treatment with the luteinizing hormone-releasing hormone agonist leuprolide in patients with benign prostatic hyperplasia

Hormonal changes resulting from long-term use of the luteinizing hormone-releasing hormone agonist leuprolide depot were studied in a randomized placebo-controlled study comprising 50 evaluable patients with benign prostatic hyperplasia (BPH). A total of 26 patients received 3.75 mg leuprolide depot intramuscularly every 28 days for 24 weeks and 24 received a placebo. The patients were followed up for a further 24-week period. Serum concentrations of luteinizing hormone decreased by 90% and follicle-stimulating hormone by 55% during the treatment period. Mean testosterone levels decreased by 96% to 0.7 nmol l-1 and dihydrotestosterone decreased by 90%. The adrenal androgens androstenedione and dehydroepiandrosterone sulphate decreased by 48 and 24%, respectively. In most patients, estradiol decreased to non-detectable values, while the decrease in estrone was 35%. There was no change in prolactin and sex hormone-binding globulin as compared to the placebo group. Hormonal changes were reversible, but the suppression of testicular hormone production was not completely normalized in all patients 24 weeks after discontinuation of the treatment.

TRH: mediator of prolactin in the prostate?

Thanks to our preoccupation with androgen ablative therapy, no significant progress has been made in combating prostate cancer (PCa) in 50 years. Also, there have been only limited advances in medical treatment of benign prostatic hyperplasia (BPH). The intent of this essay is to explore the mode of participation of prolactin (Prl) in prostatic physiology in the hope that such knowledge will reveal new avenues through which both BPH and PCa can be opposed-even prevented. An especially novel aspect of this study is the recognition of the presence and androgen- and prolactin-dependent concentration of the tripeptide, thyrotropin-releasing hormone (TRH) in prostatic tissue. It is hypothesized that, whereas TRH is the hypothalamic stimulus of hypophyseal Prl secretion, it may, in the prostate, serve as the mediator of Prl's independent and androgen-dependent controls of the gland's growth and function. Through an overview of these relationships, methods are suggested both for their study and for their adaptation to early detection and prevention of imminent pathogenesis.

Prostate cancer. Primary hormonal treatment

BACKGROUND

No other treatment matches the 40-60% objective response and up to 80% subjective responses for primary hormonal therapy in patients with symptomatic disease. This makes primary hormonal treatment first-line therapy metastatic prostate cancer.

RESULTS

The treatment outcome is determined by the initial and intermittent prognostic factors. In the multihormonal environment, several endocrine treatments have shown competing levels of response. Maximal androgen blockade has emerged as the best treatment to achieve a response and even has increased survival modestly. Monotherapy with nonsteroidal antiandrogens plays a role in patients trying to preserve their potency.

CONCLUSIONS

Pilot treatment adjusted to the medical needs and social preferences of the patient is appropriate and allows a tailored approach to the individual patient.