Risk of disease flare with LHRH agonist therapy in men with prostate cancer: Myth or fact?

Relugolix: A Review in Advanced Prostate Cancer

Relugolix (Orgovyx^®), an orally active nonpeptide gonadotropin-releasing hormone (GnRH) receptor antagonist that provides rapid testosterone suppression, is indicated in the USA for the treatment of advanced prostate cancer and in the EU for advanced hormone-sensitive prostate cancer. In the pivotal phase III HERO trial in men with advanced prostate cancer, once-daily oral relugolix (with a loading dose on day 1) led to a sustained castration rate over 48 weeks of treatment of > 90%, a rate that was non-inferior to that provided by intramuscular leuprolide depot every 3 months (with an exploratory analysis further indicating the superiority of relugolix over leuprolide). Relugolix was generally well tolerated, having an adverse event profile that is consistent with testosterone suppression. Furthermore, there is evidence that relugolix may be associated with a lower risk of major adverse cardiac events compared with leuprolide. With the ability to provide the rapid testosterone suppression (with no initial surge in testosterone upon treatment initiation) combined with the benefits of oral administration and potentially improved cardiac safety, relugolix presents a valuable treatment option for men with advanced prostate cancer where androgen deprivation therapy is indicated.

Advanced delivery of leuprorelin acetate for the treatment of prostatic cancer

INTRODUCTION

Androgen-deprivation therapy (ADT) is the main therapy for patients with advanced and metastatic prostate cancer (PCa) and, in combination with radiotherapy, for patients with localized high-risk PCa. Due to its favorable tolerability among different treatments available for ADT, leuprorelin acetate is well established as the leading luteinizing hormone-releasing hormone (LHRH) analog. The development of second-generation leuprorelin acetate (LA) depot formulation (Eligard®, Recordati S.p.A) allowed a consistent and controlled release of leuprorelin between injections and a more efficient reduction of testosterone levels with respect to conventional LHRH agonists.

AREAS COVERED

This work provides a summary of the biological and clinical rationale for using LA to manage PCa and presents the current evidence about the therapeutic activity of the LA gel depot formulation, used as an advanced leuprorelin acetate delivery method.

EXPERT OPINION

Results of the registration studies and post-marketing clinical trials demonstrate that the LA gel depot provides long-term efficacy in the clinical practice and a good degree of tolerability. Overall, collected data suggest that the LA gel depot can represent the ADT reference therapy in advanced PCa.

Androgen Flare after LHRH Initiation Is the Side Effect That Makes Most of the Beneficial Effect When It Coincides with Radiation Therapy for Prostate Cancer

Simple Summary

Prostate cancer tumor growth is stimulated by androgens. Surgical castration or medical castration using long-acting luteinizing hormone-releasing hormone (LHRH) agonists or antagonists is the backbone of the treatments of metastatic disease. Treatment of locally advanced prostate cancer was accomplished with radiation therapy alone until multiple studies showed that combining radiation therapy with LHRH agonists results in significant survival benefit. While the goal of the use of LHRH agonists was to suppress testosterone levels during radiation, we show, through review of previous studies, that survival benefit was achieved only when LHRH was initiated during the course of radiation, and thus androgen flare during the first 1–3 weeks after the initiation of LHRH is most likely the reason for higher survival. Androgens drive tumor cells into mitosis, and mitotic death is the dominant mechanism of tumor cell kill by radiation.

Abstract

Treatment of metastatic prostate cancer was historically performed via bilateral orchiectomy to achieve castration. An alternative to surgical castration is the administration of subcutaneous recombinant luteinizing hormone-releasing hormone (LHRH). LHRH causes the pituitary gland to produce luteinizing hormone (LH), which results in synthesis and secretion of testosterone from the testicles. When LHRH levels are continuously high, the pituitary gland stops producing LH, which results in reduced testosterone production by the testicles. Long-acting formulations of LHRH were developed, and its use replaced surgical orchiectomy in the vast majority of patients. Combining LHRH and radiation therapy was shown to increase survival of prostate cancer patients with locally advanced disease. Here, we present a hypothesis, and preliminary evidence based on previous randomized controlled trials, that androgen surge during radiation, rather than its suppression, could be responsible for the enhanced prostate cancer cell kill during radiation. Starting LHRH agonist on the first day of radiation therapy, as in the EORTC 22863 study, should be the standard of care when treating locally advanced prostate cancer. We are developing formulations of short-acting LHRH agonists that induce androgen flare, without subsequent androgen deprivation, which could open the door for an era in which locally advanced prostate cancer could be cured while patients maintain potency.

Follicle-stimulating hormone promotes growth of human prostate cancer cell line-derived tumor xenografts

Chemical castration in prostate cancer can be achieved with gonadotropin-releasing hormone (GnRH) agonists or antagonists. Their effects differ by the initial flare of gonadotropin and testosterone secretion with agonists and the immediate pituitary-testicular suppression by antagonists. While both suppress luteinizing hormone (LH) and follicle-stimulating hormone (FSH) initially, a rebound in FSH levels occurs during agonist treatment. This rebound is potentially harmful, taken the expression of FSH receptors (R) in prostate cancer tissue. We herein assessed the role of FSH in promoting the growth of androgen-independent (PC-3, DU145) and androgen-dependent (VCaP) human prostate cancer cell line xenografts in nude mice. Gonadotropins were suppressed with the GnRH antagonist degarelix, and effects of add-back human recombinant FSH were assessed on tumor growth. All tumors expressed GnRHR and FSHR, and degarelix treatment suppressed their growth. FSH supplementation reversed the degarelix-evoked suppression of PC-3 tumors, both in preventive (degarelix and FSH treatment started upon cell inoculation) and therapeutic (treatments initiated 3 weeks after cell inoculation) setting. A less marked, though significant FSH effect occurred in DU145, but not in VCaP xenografts. FSHR expression in the xenografts supports direct FSH stimulation of tumor growth. Testosterone supplementation, to maintain the VCaP xenografts, apparently masked the FSH effect on their growth. Treatment with the LH analogue hCG did not affect PC-3 tumor growth despite their expression of luteinizing hormone/choriongonadotropin receptor. In conclusion, FSH, but not LH, may directly stimulate the growth of androgen-independent prostate cancer, suggesting that persistent FSH suppression upon GnRH antagonist treatment offers a therapeutic advantage over agonist.

Prostate cancer

Prostate cancer is a complex disease that affects millions of men globally, predominantly in high human development index regions. Patients with localized disease at a low to intermediate risk of recurrence generally have a favourable outcome of 99% overall survival for 10 years if the disease is detected and treated at an early stage. Key genetic alterations include fusions of TMPRSS2 with ETS family genes, amplification of the MYC oncogene, deletion and/or mutation of PTEN and TP53 and, in advanced disease, amplification and/or mutation of the androgen receptor (AR). Prostate cancer is usually diagnosed by prostate biopsy prompted by a blood test to measure prostate-specific antigen levels and/or digital rectal examination. Treatment for localized disease includes active surveillance, radical prostatectomy or ablative radiotherapy as curative approaches. Men whose disease relapses after prostatectomy are treated with salvage radiotherapy and/or androgen deprivation therapy (ADT) for local relapse, or with ADT combined with chemotherapy or novel androgen signalling-targeted agents for systemic relapse. Advanced prostate cancer often progresses despite androgen ablation and is then considered castration-resistant and incurable. Current treatment options include AR-targeted agents, chemotherapy, radionuclides and the poly(ADP-ribose) inhibitor olaparib. Current research aims to improve prostate cancer detection, management and outcomes, including understanding the fundamental biology at all stages of the disease.

Prostate cancer

Prostate cancer is a complex disease that affects millions of men globally, predominantly in high human development index regions. Patients with localized disease at a low to intermediate risk of recurrence generally have a favourable outcome of 99% overall survival for 10 years if the disease is detected and treated at an early stage. Key genetic alterations include fusions of TMPRSS2 with ETS family genes, amplification of the MYC oncogene, deletion and/or mutation of PTEN and TP53 and, in advanced disease, amplification and/or mutation of the androgen receptor (AR). Prostate cancer is usually diagnosed by prostate biopsy prompted by a blood test to measure prostate-specific antigen levels and/or digital rectal examination. Treatment for localized disease includes active surveillance, radical prostatectomy or ablative radiotherapy as curative approaches. Men whose disease relapses after prostatectomy are treated with salvage radiotherapy and/or androgen deprivation therapy (ADT) for local relapse, or with ADT combined with chemotherapy or novel androgen signalling-targeted agents for systemic relapse. Advanced prostate cancer often progresses despite androgen ablation and is then considered castration-resistant and incurable. Current treatment options include AR-targeted agents, chemotherapy, radionuclides and the poly(ADP-ribose) inhibitor olaparib. Current research aims to improve prostate cancer detection, management and outcomes, including understanding the fundamental biology at all stages of the disease.

Oral Relugolix for Androgen-Deprivation Therapy in Advanced Prostate Cancer

BACKGROUND

Injectable luteinizing hormone-releasing hormone agonists (e.g., leuprolide) are the standard agents for achieving androgen deprivation for prostate cancer despite the initial testosterone surge and delay in therapeutic effect. The efficacy and safety of relugolix, an oral gonadotropin-releasing hormone antagonist, as compared with those of leuprolide are not known.

METHODS

In this phase 3 trial, we randomly assigned patients with advanced prostate cancer, in a 2:1 ratio, to receive relugolix (120 mg orally once daily) or leuprolide (injections every 3 months) for 48 weeks. The primary end point was sustained testosterone suppression to castrate levels (<50 ng per deciliter) through 48 weeks. Secondary end points included noninferiority with respect to the primary end point, castrate levels of testosterone on day 4, and profound castrate levels (<20 ng per deciliter) on day 15. Testosterone recovery was evaluated in a subgroup of patients.

RESULTS

A total of 622 patients received relugolix and 308 received leuprolide. Of men who received relugolix, 96.7% (95% confidence interval [CI], 94.9 to 97.9) maintained castration through 48 weeks, as compared with 88.8% (95% CI, 84.6 to 91.8) of men receiving leuprolide. The difference of 7.9 percentage points (95% CI, 4.1 to 11.8) showed noninferiority and superiority of relugolix (P<0.001 for superiority). All other key secondary end points showed superiority of relugolix over leuprolide (P<0.001). The percentage of patients with castrate levels of testosterone on day 4 was 56.0% with relugolix and 0% with leuprolide. In the subgroup of 184 patients followed for testosterone recovery, the mean testosterone levels 90 days after treatment discontinuation were 288.4 ng per deciliter in the relugolix group and 58.6 ng per deciliter in the leuprolide group. Among all the patients, the incidence of major adverse cardiovascular events was 2.9% in the relugolix group and 6.2% in the leuprolide group (hazard ratio, 0.46; 95% CI, 0.24 to 0.88).

CONCLUSIONS

In this trial involving men with advanced prostate cancer, relugolix achieved rapid, sustained suppression of testosterone levels that was superior to that with leuprolide, with a 54% lower risk of major adverse cardiovascular events. (Funded by Myovant Sciences; HERO ClinicalTrials.gov number, NCT03085095.).

Safety of testosterone therapy in men with prostate cancer

Introduction: The use of testosterone therapy (TTh) in men with prostate cancer (PCa) is relatively new, and controversial, due to the longstanding maxim that TTh is contraindicated in men with PCa. Scientific advances have prompted a reevaluation of the potential role for TTh in men with PCa, particularly as TTh has been shown to provide important symptomatic and general health benefits to men with testosterone deficiency (TD), including many men with PCa who may expect to live 30-50 years after diagnosis. Areas covered: This review outlines the historical underpinnings of the historical belief that TTh 'fuels' PCa and the experimental and clinical studies that have radically altered this view, including description of the saturation model. The authors review studies of TTh in men with PCa following radical prostatectomy and radiation therapy, in men on active surveillance, and in men with advanced or metastatic PCa. Expert opinion: TTh provides important symptomatic and overall health benefits for men with PCa who have TD. Although more safety studies are needed, TTh is a reasonable therapeutic option for men with low-risk PCa after surgery or radiation. Data in men on active surveillance are limited, but initial reports are reassuring.

Metastatic prostate cancer remains incurable, why?

Metastatic prostate cancer patients present in two ways-with already disseminated disease at the time of presentation or with disease recurrence after definitive local therapy. Androgen deprivation therapy is given as the most effective initial treatment to patients. However, after the initial response, almost all patients will eventually progress despite the low levels of testosterone. Disease at this stage is termed castration resistant prostate cancer (CRPC). Before 2010, the taxane docetaxel was the first and only life prolonging agent for metastatic CRPC (mCRPC). The last decade has witnessed robust progress in CRPC therapeutics development. Abiraterone, enzalutamide, apalutamide and sipuleucel-T have been evaluated as first- and second-line agents in mCRPC patients, while cabazitaxel was approved as a second-line treatment. Radium-223 dichloride was approved in symptomatic patients with bone metastases and no known visceral metastases pre- and post-docetaxel. However, despite significant advances, mCRPC remains a lethal disease. Both primary and acquired resistance have been observed in CRPC patients treated by these new agents. It could be solely cell intrinsic or it is possible that the clonal heterogeneity in treated tumors may result from the adaptive responses to the selective pressures within the tumor microenvironment. The aim of this review is to list current treatment agents of CRPC and summarize recent findings in therapeutic resistance mechanisms.

Patterns of Bicalutamide Use in Prostate Cancer Treatment: A U.S. Real-World Analysis Using the SEER-Medicare Database

INTRODUCTION

Bicalutamide (BIC), a non-steroidal anti-androgen, is FDA-indicated for use in combination with a luteinizing hormone-releasing hormone (LHRH) analog for treatment of Stage D2 metastatic carcinoma of the prostate. Lack of consensus exists regarding the clinical benefit of BIC use, either alone or combined use of BIC with an LHRH analog or antagonist (combined androgen blockade or CAB), versus treatment with androgen deprivation therapy (ADT) alone.

METHODS

The SEER-Medicare database was used to identify prostate cancer patients aged ≥ 66 years diagnosed between 2007 and 2011 and who filled at least one prescription for BIC. Duration of BIC treatment was assessed in relation to ADT use; either alone (monotherapy), as part of CAB only, and as part of CAB followed by monotherapy. Additionally, we assessed use of BIC during or outside a potential testosterone flare prevention period (initiation within 2 months of an LHRH agonist).

RESULTS

A total of 7521 prostate cancer patients who filled a prescription for BIC were identified. Eighteen percent of the cohort used BIC alone, over half the patients (54%) used BIC as part of CAB and 27% used BIC as part of CAB followed by monotherapy. Among men treated with BIC as part of CAB, 58% received BIC only within the potential flare period.

CONCLUSIONS

Although there is no FDA indication for BIC use as monotherapy, > 44% of patients in this study used BIC alone or as part of CAB followed by monotherapy. Further research is necessary to understand the outcomes of BIC utilization in these settings, particularly compared with newer second-generation anti-androgens.

FUNDING

Medivation LLC, a Pfizer company, and Astellas, Pharma, Inc.

Risk of Testosterone Flare in the Era of the Saturation Model: One More Historical Myth

CONTEXT

When luteinizing hormone-releasing hormone (LHRH) agonists were introduced in the 1980s, it was universally believed that the initial transient rise in serum testosterone (T), termed T flare, caused rapid prostate cancer (PCa) growth and led to disease progression, complications, and death. It became routine to offer antiandrogens (AAs) to prevent these risks. However, over the last decade, it has become recognized that androgens have a finite ability to stimulate PCa growth (the saturation model), providing a theoretical challenge to the risks of T flare.

OBJECTIVE

To review evidence for the risks associated with T flare from a modern perspective, specifically prostate-specific antigen (PSA) flare, disease progression, and spinal cord compression.

EVIDENCE ACQUISITION

An Ovid Medline database search was conducted to identify articles related to "testosterone flare", "disease flare", and "PSA flare" associated with LHRH agonists. The literature review included papers published from May 1, 1980 through May 1, 2016. Key search terms included, luteinizing hormone-releasing hormone, gonadotropin-releasing hormone, and antiandrogens.

EVIDENCE SYNTHESIS

Initial administration of LHRH agonists uniformly results in peak increases in serum T by 40-100% on days 2-3, returning to baseline by days 7-8, after which T declines to castrate levels by approximately 2-3 wk. Of six LHRH agonist studies reporting PSA during the period of T flare, five showed no significant rise in PSA despite the presence of advanced disease with mean baseline PSA as high as ≥500ng/ml. Evidence for disease flare was limited to one report of greater bone pain with LHRH agonists alone versus LHRH agonists with AAs. Three other RCTs reported no disease flare. Rates of spinal cord compression were no greater for LHRH agonists alone compared with castration or estrogen treatment. We identified no studies of men treated with LHRH agonists versus placebo/no treatment to assess the effects of LHRH agonists compared with the natural history of advanced PCa.

CONCLUSIONS

Although T flare has been considered risky for 30 yr, a modern review of the evidence collected primarily in the 1980s and 1990s fails to support this view. Specifically, T flare does not appear to be associated with significantly increased PSA, disease progression, or adverse events, even in men with widely metastatic disease. These results are consistent with the saturation model, first introduced in 2006. There seems little value in adding AA to LHRH agonists, except possibly for men with extensive vertebral metastases and serum T concentrations well below the saturation point of approximately 250ng/dl (8.7nmol/l).

PATIENT SUMMARY

A review of the literature reveals no evidence for increased risks associated with testosterone flare from the initiation of luteinizing hormone-releasing hormone (LHRH) agonists. This appears to be an unsupported belief from an earlier era when our understanding of testosterone's relationship to prostate cancer was less sophisticated. Except in rare instances, there appears to be no need to use an androgen blocker when beginning treatment with LHRH agonists.

Pituitary Apoplexy After Initial Leuprolide Injection

BACKGROUND

Pituitary apoplexy is a rare complication of the initial administration of leuprolide acetate.

CASE DESCRIPTION

We present the case of a 63-year-old man who experienced headache, blurred vision, and loss of consciousness after initial leuprolide treatment for prostate carcinoma. Neuroimaging showed pituitary hemorrhage.

CONCLUSIONS

Clinicians should be aware of this rare but known complication of leuprolide injection so that prompt diagnosis and treatment initiation are performed in patients with leuprolide-associated pituitary apoplexy.