Efficacy and safety of androgen deprivation therapy after switching from monthly leuprolide to monthly degarelix in patients with prostate cancer

Real-World Evidence Prediction of a Phase IV Oncology Trial: Comparative Degarelix vs Leuprolide Safety

BACKGROUND

Medical and regulatory communities are increasingly interested in the utility of real-world evidence (RWE) for answering questions pertaining to drug safety and effectiveness but concerns about validity remain. A principled approach to conducting RWE studies may alleviate concerns and increase confidence in findings. This study sought to predict the findings from the PRONOUNCE trial using a principled approach to generating RWE.

METHODS

This propensity-score (PS) matched observational cohort study utilized 3 claims databases to compare the occurrence of major adverse cardiovascular events (MACE) among initiators of degarelix vs. leuprolide. Patients were included if they had history of prostate cancer and atherosclerotic cardiovascular disease. Subjects were excluded if they didn't have continuous database enrollment in the year prior to treatment initiation, were exposed to androgen deprivation therapy or experienced an acute cardiovascular event within 30 days prior to treatment initiation, or had a history or risk factors of QT prolongation.

RESULTS

There were 12,448 leuprolide and 1,969 degarelix study-eligible patients before matching, with 1,887 in each arm after PS-matching. The results for MACE comparing degarelix to leuprolide in the observational analysis (hazard ratio= 1.35; 95% confidence interval = 0.94-1.93) was consistent with the subsequently released PRONOUNCE result (hazard ratio = 1.28; 95% confidence interval = 0.59-2.79).

CONCLUSIONS

This study successfully predicted the result of a comparative cardiovascular safety trial in the oncology setting. Although the findings are encouraging, limitations of measuring cancer stage and tumor progression are representative of challenges in attempting to generalize whether claims-based RWE can be used as actionable evidence.

Testosterone analysis in prostate cancer patients

Testosterone is an essential steroid hormone associated with a wide variety of biological processes in humans. In prostate cancer, androgen signaling is an important driver of tumor cell growth. Depletion of gonadal testosterone, achieved by surgical or chemical castration, prevents androgenic signaling and temporally reduces, stops or reverses tumor growth before inevitable progression to castration-resistant prostate cancer occurs. Additional treatment strategies targeting androgenic signaling have become available, although these are without curative intent. While circulating testosterone is also associated with disease risk and potential clinical utility, the main use in the clinical lab is monitoring adequate castration and subsequent resistance to therapy. Adequate castrate testosterone concentrations are currently based on over 50 year-old double-isotope derivative assays that are disputed in automated immunoassay (IA) analysis. The debate has been further fueled with the introduction of mass spectrometry-based assays for testosterone, offering a substantial increase in sensitivity and specificity. In this review, we discuss testosterone regulation and androgen deprivation therapy in prostate cancer. We provide an overview of the developments in testosterone analysis for monitoring adequate castration and resistance to therapy. Current clinical practice and future clinical utility will be discussed. Finally, clinical and research recommendations will be presented.

Switching from a gonadotropin-releasing hormone (GnRH) agonist to a GnRH antagonist in prostate cancer patients: A systematic review and meta-analysis

INTRODUCTION

We sought to address whether there are clinical responses when patients who are failing gonadotropin-releasing hormone (GnRH) agonist therapy are switched to degarelix. Androgen-deprivation therapy remains the backbone of treatment for disseminated prostate cancer and may be achieved with orchiectomy, GnRH agonists, or degarelix, a GnRH antagonist.

METHODS

We conducted a systematic review and meta-analysis with a search of the BIOSIS Previews, Embase, International Pharmaceutical Abstracts, MEDLINE, and Google Scholar databases using key terms. Quantitative meta-analysis was performed to provide a pooled estimate of prostate specific antigen (PSA) response at three months.

RESULTS

Thirteen studies were identified, eight of which were included in the qualitative and quantitative analyses. Patient characteristics were broadly similar between the studies. Out of 155 patients across all included studies, 20 had stable PSA after the switch (12.9%), 14 had a 10-30% decrease in PSA (9.0%), three had a 30-50% decrease (1.9%), and 13 had a more than 50% decrease (8.4%). Random effects meta-analysis of these data demonstrated a pooled response rate of 27.75% (95% confidence interval 18.9-36.5%; I²=7.9%). Changes in testosterone levels following the switch could not be quantitatively assessed due to lack of sufficient data.

CONCLUSIONS

Our results suggest that a switch to GnRH antagonist following progression on a GnRH agonist may result in a stable or decreased PSA at three months in about 30% of patients. This information should be considered among the potential options to discuss with patients with a rising PSA on GnRH agonist therapy.

[Castration modalities in prostate cancer: Are they all equal?]

AIM

The aim of this literature review was to focus on the new highlights regarding oncologic and safety outcomes depending on the type of castration used.

MATERIAL

Literature search using various algorithms "prostate cancer", "castration", "agonist", "antagonist", "orchiectomy", "GnRH", "FSH", "androgen deprivation therapy" has been performed in April 2015, through the PubMed and Embase databases.

RESULTS

GnRH agonists and antagonists are both currently used in clinical practice. Nevertheless, differences regarding their pharmacologic properties have been highlighted in recent studies, specifically regarding the rapidity, sustainability and depth of the castration, but also the decrease in FSH level. Such differences may have oncological impact on the patient, regarding the disease biological control and the time to progression, and a tolerability impact, especially on the cardiovascular risks. The role of the depth and the sustainability of the castration in one hand, the FSH impact in the other hand, as well as a direct inhibition on extra-pituitary GnRH receptors by antagonist might explain these differences.

CONCLUSIONS

Recent studies suggest differences between GnRH agonists and antagonist that could impact the patient clinical outcomes. However, further high level of evidence comparative studies remains warranted.

Clinical Effect of Switching from a Luteinizing Hormone-Releasing Hormone Agonist to an Antagonist in Patients with Castration-Resistant Prostate Cancer and Serum Testosterone Level ≥ 20 ng/dl

INTRODUCTION

The efficacy of conversion from a luteinizing hormone-releasing hormone agonist to an antagonist was evaluated prospectively in patients with castration-resistant prostate cancer.

MATERIALS AND METHODS

From October 2012 to December 2014, 8 cases with a serum testosterone level ≥ 20 ng/dl during following androgen deprivation therapy were enrolled and received degarelix monthly. The primary end-pointgoal was to determine the effective prostate-specific antigen response rate. The secondary end-pointgoal was to assess the proportion of cases with a decrease in serum testosterone level to < 20 ng/ml.

RESULTS

One patient achieved a complete response, with a prostate-specific antigen level of 0.02 ng/ml at the nadirend of the study. The effective response rate was 25.0% (2/8), and the proportion of cases with prostate-specific antigen decline was 62.5% (5/8). In 5/8 cases (5/8, 62.5%), serum testosterone levels declined to < 20 ng/dl.

CONCLUSION

Switching to a luteinizing hormone-releasing hormone antagonist in patients with testosterone levels ≥ 20 ng/dl may be an option in sequential androgen deprivation therapy for some patients.

Follicle-Stimulating Hormone Receptor Expression in Endometriotic Lesions and the Associated Vasculature: An Immunohistochemical Study

Follicle-stimulating hormone receptor (FSHR) is present on endothelial cells of blood vessels and endometrial glands of the proliferative and secretory endometrium. So far, the expression of FSHR in endometriosis has not been studied. We evaluated FSHR expression in 194 tissue specimens representing 3 relevant types of endometriosis: rectovaginal endometriotic nodules, ovarian endometriotic cysts, and peritoneal endometriotic implants. Specimens of normal endometrium were used as controls. Archival formalin-fixed and paraffin-embedded material was analyzed immunohistochemically with a highly specific monoclonal antihuman FSHR antibody using the peroxidase method. A robust vascular FSHR expression was found in all 194 patients, irrespective of the endometriosis lesion location. Follicle-stimulating hormone receptor was not detected in normal host tissues located more than 5 mm from the lesions. The endometriotic lymphatic vessels do not express FSHR. The density of FSHR-positive vessels in patients with rectovaginal endometriotic nodules was 46.0 ± 5.7 vessels/mm(2) Similar values were obtained for ovarian endometriotic cysts and peritoneal endometriosis. The density of FSHR-positive vessels associated with the core of rectovaginal endometriotic nodules was 2-fold higher than that of the perilesional, adjacent normal host tissue (64.2 ± 8.2 vs 27.2 ± 3.2 vessels/mm(2), respectively). Expression of FSHR was also detected either in endometriotic glandular epithelial cells, endometriotic stromal cells, or in both cell types (23%, 25%, and 21% of patients, respectively). Normal endometrium expressed FSHR predominately in basalis, in a cellular distribution dependent on hormonal environment. In conclusion, our data suggest novel FSHR expression in endometriotic lesions, qualitatively and quantitatively different from that of normal endometrium.

Gonadotropin-releasing hormone antagonists versus standard androgen suppression therapy for advanced prostate cancer A systematic review with meta-analysis

OBJECTIVES

To evaluate efficacy and safety of gonadotropin-releasing hormone (GnRH) antagonists compared to standard androgen suppression therapy for advanced prostate cancer.

SETTING

The international review team included methodologists of the German Cochrane Centre and clinical experts.

PARTICIPANTS

We searched CENTRAL, MEDLINE, Web of Science, EMBASE, trial registries and conference books for randomised controlled trials (RCT) for effectiveness data analysis, and randomised or non-randomised controlled studies (non-RCT) for safety data analysis (March 2015). Two authors independently screened identified articles, extracted data, evaluated risk of bias and rated quality of evidence according to GRADE.

RESULTS

13 studies (10 RCTs, 3 non-RCTs) were included. No study reported cancer-specific survival or clinical progression. There were no differences in overall mortality (RR 1.35, 95% CI 0.63 to 2.93), treatment failure (RR 0.91, 95% CI 0.70 to 1.17) or prostate-specific antigen progression (RR 0.83, 95% CI 0.64 to 1.06). While there was no difference in quality of life related to urinary symptoms, improved quality of life regarding prostate symptoms, measured with the International Prostate Symptom Score (IPSS), with the use of GnRH antagonists compared with the use of standard androgen suppression therapy (mean score difference -0.40, 95% CI -0.94 to 0.14, and -1.84, 95% CI -3.00 to -0.69, respectively) was found. Quality of evidence for all assessed outcomes was rated low according to GRADE. The risk for injection-site events was increased, but cardiovascular events may occur less often by using GnRH antagonist. Available evidence is hampered by risk of bias, selective reporting and limited follow-up.

CONCLUSIONS

There is currently insufficient evidence to make firm conclusive statements on the efficacy of GnRH antagonist compared to standard androgen suppression therapy for advanced prostate cancer. There is need for further high-quality research on GnRH antagonists with long-term follow-up.

TRIAL REGISTRATION NUMBER

CRD42012002751.

Degarelix: a review of its use in patients with prostate cancer

Degarelix (Firmagon(®); Gonax(®)) is a gonadotropin-releasing hormone receptor antagonist that is approved for the treatment of advanced (hormone-dependent) prostate cancer in the US and EU and the treatment of prostate cancer in Japan. In a pivotal randomized, controlled, 12-month phase III study, degarelix (initial subcutaneous dose of 240 mg followed by monthly dosages of 80 mg) was noninferior to leuprolide (monthly intramuscular dosages of 7.5 mg) in patients with prostate cancer of any stage for which endocrine treatment was indicated (except neoadjuvant hormonal therapy) with regard to suppression of testosterone to castration levels (i.e. ≤0.5 ng/mL). Suppression of testosterone and prostate-specific antigen (PSA) levels was faster with degarelix than with leuprolide, and no testosterone surges or microsurges were seen in degarelix recipients. Suppression of testosterone and PSA levels was maintained for the 12-month study duration and continued for up to 5 years in an extension to the main trial (including in patients switching from leuprolide to degarelix in the extension). The drug was generally well tolerated, with most adverse events being mild to moderate in severity. Injection-site reactions and events reflecting the expected effects of testosterone suppression (e.g. hot flushes, weight increase) were the most common treatment-emergent adverse events. Thus, degarelix is a useful option for the treatment of prostate cancer in patients for whom endocrine treatment is indicated.

Bench-to-bedside development of agonists and antagonists of luteinizing hormone-releasing hormone for treatment of advanced prostate cancer

BACKGROUND

Androgen deprivation therapy (ADT) has been the standard of care for treating patients with hormone-sensitive advanced prostate cancer (PCa) for 3 decades. The agonists of luteinizing hormone-releasing hormone (LHRH), also called gonadotropin-releasing hormone, are still the most frequently used form of medical ADT.

ADT AND LHRH ANALOGS

The application of agonists of LHRH has improved and modernized the treatment of advanced PCa; millions of patients have benefited from therapy with LHRH agonists as a preferred alternative to surgical castration, as the psychological effects and perpetuity of orchiectomy are undesirable for most men. Despite their efficacy, agonists of LHRH have several shortcomings, including initial surge in testosterone, producing exacerbation of clinical symptoms, and microsurges in testosterone that might occur after each administration. A new, alternate approach to ADT is emerging with the improvements in antagonists of LHRH. This class of LHRH analogues produces a direct and immediate blockade of pituitary LHRH receptors and leads to a more rapid suppression of testosterone without an initial surge or subsequent microsurges. Degarelix, a third-generation LHRH antagonist, is the only antagonist with a low histamine-releasing activity that is currently on the market for clinical use in advanced PCa with improved testosterone suppression, better control of follicle-stimulating hormone and prostate-specific antigen, and which offers a prolonged delay to progression and more favorable effects on serum alkaline phosphatase.

CONCLUSIONS

Although LHRH agonists are still the mainstay for treatment of advanced PCa, antagonists of LHRH offer an alternative as a pharmacological approach.

Evaluation of histopathological findings at the injection site following degarelix administration

PURPOSE

The aims of the present study were to investigate the incidence of injection site reactions (ISRs) following administration of 240 mg degarelix and identify the risk factors for ISRs.

METHODS

This study was conducted in 50 consecutive men treated with degarelix for the first time. ISRs after an initial degarelix dose of 240 mg (administered subcutaneously as two 3 ml subcutaneous injection) were evaluated using the five categories of the Common Terminology Criteria for Adverse Events Version 4 of the National Cancer Institute. We also assessed the differences in patient background between patients with and without an ISR.

RESULTS

The mean age of patients and prostate-specific antigen (PSA) level just before degarelix administration were 75.6 and 198.4 ng/ml, respectively. Hormonal therapy with degarelix was administered for the first time to 33 patients; 11 of the 50 patients were receiving an oral steroid, 6 for prostate cancer, 1 for hematological disease, and 4 for allergic conditions. ISRs were observed in 25 patients, and all of the ISRs were categorized as grade 1 or 2; however, 2 patients discontinued this procedure due to the ISR. Significant differences in the first experience with subcutaneous therapy (p = 0.007) and rate of combination with a steroid (p = 0.017) were observed between patients with and without ISRs.

CONCLUSION

The incidences of ISRs in patients receiving subcutaneous therapy for the first time and in patients also receiving an oral steroid were 64 and 18 %, respectively. Patients should be provided with information concerning the possible occurrence of ISR due to degarelix prior to the administration, particularly patients who are not receiving steroids and patients who have no experience with subcutaneous injections.

An update on the use of degarelix in the treatment of advanced hormone-dependent prostate cancer

Androgen deprivation therapy remains the mainstay of medical treatment for advanced prostate cancer. Commonly, this is achieved with medical androgen deprivation rather than surgical intervention as the permanence and psychological effects of the latter are unacceptable for most patients. Degarelix is a third generation antagonist of luteinizing hormone-releasing hormone (LHRH, also termed gonadotropin-releasing hormone) for the first-line treatment of androgen-dependent advanced prostate cancer. Degarelix acts directly on the pituitary receptors for LHRH, blocking the action of endogenous LHRH. The use of degarelix eliminates the initial undesirable surge in gonadotropin and testosterone levels, which is produced by agonists of LHRH. Degarelix is the most comprehensively studied and widely available LHRH antagonist worldwide. Clinical trials have demonstrated that degarelix has a long-term efficacy similar to the LHRH agonist leuprolide in achieving testosterone suppression in patients with prostate cancer. Degarelix, however, produces a faster suppression of testosterone and prostate-specific antigen (PSA), with no testosterone surges or microsurges, and thus prevents the risk of clinical flare in advanced disease. Recent clinical trials demonstrated that treatment with degarelix results in improved disease control when compared with an LHRH agonist in terms of superior PSA progression-free survival, suggesting that degarelix likely delays progression to castration-resistant disease and has a more significant impact on bone serum alkaline phosphatase and follicle-stimulating hormone. Degarelix is usually well tolerated, with limited toxicity and no evidence of systemic allergic reactions in clinical studies. Degarelix thus represents an important addition to the hormonal armamentarium for therapy of advanced androgen-dependent prostate cancer.

[Androgen deprivation therapy for prostate cancer and osteoporotic risk]

Androgen deprivation therapy represents an important part of the management of prostate cancer. However, epidemiological data have shown that it is a well-established cause of osteoporosis and increased risk of fracture. So far no consensus guidelines have been published regarding the screening and treatment of osteoporosis in men with prostate cancer. Here we report the design of a new questionnaire, derived from the FRAX(®) ("Fracture Risk Assessment Tool") algorithm, to evaluate the risk of fracture in those patients. In accordance with recent reviews and on the basis of their experience, our French board of experts recommends systematic screening for osteoporosis with dual energy x- ray absorptiometry scans, practice of exercise and calcium and vitamin D supplementation, and selective treatment with bisphosphonates in men at greatest osteoporotic risk.

[Change of the LHRH analogue in progressive castration-refractory prostate cancer]

INTRODUCTION

Medicinal or surgical castration remains the treatment of choice in metastatic, hormone-naive prostate cancer; however, 2-12% of patients never reach the target serum levels for medicinal castration. We analyzed the therapeutic efficacy of triptorelin pamoate (TP) as salvage treatment due to its higher potency than endogenous luteinizing hormone-releasing hormone (LHRH). The amino acid sequence of TP is identical to that of endogenous LHRH except for position 6 where L-glycine is replaced by D-tryptophane rendering the synthetic moiety less susceptible to cleavage by proteolytic enzymes.

PATIENTS AND METHODS

In this study 36 patients with prostate-specific antigen (PSA) progression following first line complete androgen blockade and antiandrogen (ADT) withdrawal were retrospectively analyzed. All patients demonstrated no or minimal metastatic disease. The PSA levels, PSA doubling time (PSADT), PSA velocity (PSAV) and testosterone serum concentrations were correlated with the therapeutic response. All patients received TP at a dose of 11.5 mg at 3-month intervals until documented progression.

RESULTS

The mean patient age was 69.2 years (range 52-79 years), the mean PSA level was 23.4 ng/ml (8.7-53.1 ng/ml) and the mean PSADT was 9.2 months (2.9-15.4 months). Mean testosterone serum concentration was 38.67 ng/dl (21-76 ng/dl), the mean time between start of ADT and progression was 42.4 months (13-76 months) and the median time was 46.8 months (16-82 months). A PSA decrease of ≥50% was reached in 9 out of 36 (25%) patients, 3 out of 36 (13.9%) patients each demonstrated stable PSA levels and a prolongation of PSADT from 6.2 to 9.8 months. Mean progression-free survival (PFS) was 21.4 weeks (7-53 weeks). PSA-responders exhibited a PFS of 53.2 weeks (26-64 weeks) as compared to 28 weeks (17-35 weeks) in nonresponders. PSA responders demonstrated significantly higher testosterone serum concentrations of 48.3 ng/dl (29-76 ng/dl) as compared to nonresponders with 32.6 ng/dl (21-62 ng/dl, p=0.02). Mean follow-up was 31.4 months (27-39 months), overall survival was 80.5% and cancer-specific survival was 88.9%.

CONCLUSION

Changing the LHRH analogue in castration-refractory prostate cancer (CRPC) with testosterone serum concentrations at or above the castration level results in a temporary PSA response. This treatment option might be included in the therapeutic algorithm of CRPC. Although the PFS is short it allows the continuation of a treatment option with minimal side effects in a mere palliative situation. The data underline the need for continuous monitoring of testosterone during treatment with LHRH analogues.

A switch from GnRH agonist to GnRH antagonist in castration-resistant prostate cancer patients leads to a low response rate on PSA

PURPOSE

At the time of castration resistance, it is recommended to realize hormonal manipulations before chemotherapy. We evaluated the impact of a switch from GnRH agonist to antagonist in patients with castration-resistant prostate cancer on PSA and testosterone levels at 3 months.

METHODS

Retrospectively, 17 patients from 5 different centers undergoing androgen deprivation therapy and presenting rising PSA confirmed on 3 blood samples 2 weeks apart and despite a castrate testosterone level (<0.5 ng/ml) were reviewed. Antiandrogen withdrawal syndrome had been tested before the switch. Degarelix was administered as followed: 240 mg for the first injection and then 80 mg every month, subcutaneously. We evaluated the PSA and testosterone level variation 3 months after the switch. Patients who experienced a variation in PSA of less than 10% compared to the baseline or who had a more than 10% PSA decrease were defined as responders.

RESULTS

Mean PSA level at the switch was 34.3 ± 50.3 ng/ml, with a mean testosterone level of 0.21 ± 0.13 ng/ml. Three months after the switch, mean PSA level was 59.9 ± 81.6 ng/ml (P = 0.061), with a mean testosterone level of 0.19 ± 0.08 ng/ml (P = 0.086). At 3 months, 4 patients (23%) responded to therapy. Thirteen patients (77%) experienced a rise in PSA of more than 10% compared to baseline; 41% of patients decreased their testosterone level. The limitations of this study are its retrospective nature and the limited number of patients.

CONCLUSION

Switch from an agonist to an antagonist of GnRH has a limited impact on PSA at 3 months in castration-resistant prostate cancer patients.