Optimal Control of Testosterone: A Clinical Case-Based Approach of Modern Androgen-Deprivation Therapy

[Management of testosterone in advanced hormone-sensitive prostate cancer: still up to date?]

Androgen-deprivation therapy (ADT) is the standard therapy used for advanced or metastatic prostate cancer, either alone or in association with additional procedures and substances. The optimum value of testosterone postulated more than 40 years ago was arbitrarily set to be < 50 ng/dL or < 1.7 nmol/L and, from today's perspective, was defined by more insensitive measurement methods. Since then, more and more data has been generated, suggesting that a value of < 20 ng/dL would be prognostically relevant. Yet no guideline has been changed so far despite the call for lowering the target value. Measuring testosterone to evaluate the response to androgen suppression is not yet established in clinical routine. There are no specific recommendations in national and international guidelines. Based on the evolving evidence, the question about testosterone management during ADT is gaining importance. The current data is summarised in this paper.

Cardiovascular Effects of Androgen Deprivation Therapy in Prostate Cancer: Contemporary Meta-Analyses

Androgen deprivation therapy is a cornerstone of prostate cancer treatment. Pharmacological androgen deprivation includes gonadotropin-releasing hormone agonism and antagonism, androgen receptor inhibition, and CYP17 (cytochrome P450 17A1) inhibition. Studies in the past decade have raised concerns about the potential for androgen deprivation therapy to increase the risk of adverse cardiovascular events such as myocardial infarction, stroke, and cardiovascular mortality, possibly by exacerbating cardiovascular risk factors. In this review, we summarize existing data on the cardiovascular effects of androgen deprivation therapy. Among the therapies, abiraterone stands out for increasing risk of cardiac events in meta-analyses of both randomized controlled trials and observational studies. We find a divergence between observational studies, which show consistent positive associations between androgen deprivation therapy use and cardiovascular disease, and randomized controlled trials, which do not show these associations reproducibly.

Measuring testosterone and testosterone replacement therapy in men receiving androgen deprivation therapy for prostate cancer: A survey of UK uro-oncologists' opinions and practice

AIM

To explore the practice and attitudes of uro-oncologists in the UK regarding monitoring testosterone levels and the use of testosterone replacement therapy (TRT) in their prostate cancer patients treated with androgen deprivation therapy (ADT).

METHODS

An expert-devised online questionnaire was completed by the members of the British Uro-oncology Group (BUG).

RESULTS

Of 160 uro-oncologists invited, 84 completed the questionnaire. Before initiating ADT in patients with non-metastatic prostate cancer, only 45% of respondents measured testosterone levels and 61% did not measure testosterone at all during ADT in the adjuvant or neoadjuvant setting. However, in men with metastatic prostate cancer, 71% of the uro-oncologists measured testosterone before starting ADT and the majority continued testing during treatment. Approximately two-thirds of respondents did not prescribe TRT for their patients who were in remission following neo(adjuvant) ADT and who had castration levels of testosterone.

DISCUSSION

Among UK uro-oncologists, the measurement of testosterone levels before and during ADT was not typically part of routine practice in the management of patients with prostate cancer. However, testosterone levels were checked more frequently for patients with metastatic disease than disease at an earlier stage. Testing could be conducted in parallel with PSA measurement as testosterone levels are linked to biochemical failure. The majority of specialists participating in the survey did not prescribe TRT for their patients in remission following ADT.

CONCLUSION

Uro-oncologists in the UK do not generally measure testosterone as part of their patient management and they remain cautious about the possible benefits of TRT in men with prostate cancer.

Pharmacotherapeutic Targeting of G Protein-Coupled Receptors in Oncology: Examples of Approved Therapies and Emerging Concepts

G protein-coupled receptors (GPCRs) are involved in numerous physio-pathological processes, including the stimulation of cancer progression. In this regard, it should be mentioned that although GPCRs may represent major pharmaceutical targets, only a few drugs acting as GPCR inhibitors are currently used in anti-tumor therapies. For instance, certain pro-malignancy effects mediated by GPCRs are actually counteracted by the use of small molecules and peptides that function as receptor antagonists or inverse agonists. Recently, humanized monoclonal antibodies targeting GPCRs have also been developed. Here, we review the current GPCR-targeted therapies for cancer treatment, summarizing the clinical studies that led to their official approval. We provide a broad overview of the mechanisms of action of the available anti-cancer drugs targeting gonadotropin-releasing hormone, somatostatin, chemokine, and Smoothened receptors. In addition, we discuss the anti-tumor potential of novel non-approved molecules and antibodies able to target some of the aforementioned GPCRs in different experimental models and clinical trials. Likewise, we focus on the repurposing in cancer patients of non-oncological GPCR-based drugs, elucidating the rationale behind this approach and providing clinical evidence on their safety and efficacy.

The role of gonadotrophin-releasing hormone antagonists in the treatment of patients with advanced hormone-dependent prostate cancer in the UK

Purpose

Comparing gonadotrophin-releasing hormone (GnRH) antagonists and agonists as androgen deprivation therapy for advanced prostate cancer (PC).

Methods

This article stems from a round-table meeting in December 2014 to compare the properties of GnRH agonists and antagonists in the published literature in order to identify the patient groups most likely to benefit from GnRH antagonist therapy. A broad PubMed and congress abstract search was carried out in preparation for the meeting to ensure that the latest data and opinion were available for the discussions.

Results

In randomised, controlled trials, GnRH antagonist therapy provides more rapid suppression of luteinising hormone, follicle-stimulating hormone and testosterone than GnRH agonist treatment. Compared with the GnRH agonist, there is evidence of improved disease control by a GnRH antagonist, with longer interval to prostate-specific antigen progression and greater reduction of serum alkaline phosphatase. In a post hoc analysis of six randomised trials, the risk of cardiac events within 1 year of initiating therapy was significantly lower among men receiving GnRH antagonist than agonist. Pre-clinical laboratory data suggest a number of mechanisms whereby GnRH antagonist therapy may benefit men with pre-existing cardiovascular disease (CVD), the most plausible hypothesis being that, unlike GnRH agonists, GnRH antagonists do not activate T lymphocytes, which act to increase atherosclerotic plaque rupture.

Conclusion

When making treatment decisions, clinicians should consider comorbidities, particularly CVD, in addition to effects on PC. GnRH antagonists may be appropriate in patients with significant CV risk, existing osteopenia, lower urinary tract symptoms and significant metastatic disease.

Surgical castration efficiently delays the time of starting a systemic chemotherapy in castration-resistant prostate cancer patients refractory to initial androgen-deprivation therapy

Background

The aim of this study was to investigate the effects of surgical castration, particularly delaying the time to entrance of systemic chemotherapy, in castration-resistant prostate cancer (CRPC) patients who were refractory to initial combination androgen deprivation therapy.

Materials and methods

We analyzed the clinical data of 14 CRPC patients diagnosed at Seoul National University Bundang Hospital (SNUBH) from November 2008 through May 2015. After exclusion of three patients, we finally analyzed the baseline characteristics of 11 CRPC patients. We also assessed the delaying time of docetaxel administration, which was defined as response duration, after surgical castration.

Results

After bilateral orchiectomy, the treatment response rate was 45.4% and the median duration of response was 9 months (range 4–48 mo). Responders had less aggressive biopsy Gleason scores compared to nonresponders. Notably, responders showed the reducing pattern of serum prostate specific antigen levels, while nonresponders demonstrated increasing tendency after surgical castration. Moreover, responders also presented with a reduction pattern of serum testosterone levels, whereas nonresponders showed an increasing pattern of testosterone levels after bilateral orchiectomy.

Conclusions

In summary, despite the limited number of cases for convincing evidence, our results shed light again on the clinical benefits of surgical castration prior to the systemic chemotherapy in some CRPC patients after initial hormone therapy.

Nadir testosterone within first year of androgen-deprivation therapy (ADT) predicts for time to castration-resistant progression: a secondary analysis of the PR-7 trial of intermittent versus continuous ADT

PURPOSE

Three small retrospective studies have suggested that patients undergoing continuous androgen deprivation (CAD) have superior survival and time to progression if lower castrate levels of testosterone (< 0.7 nmol/L) are achieved. Evidence from prospective large studies has been lacking.

PATIENTS AND METHODS

The PR-7 study randomly assigned patients experiencing biochemical failure after radiation therapy or surgery plus radiation therapy to CAD or intermittent androgen deprivation. The relationship between testosterone levels in the first year and cause-specific survival (CSS) and time to androgen-independent progression in men in the CAD arm was evaluated using Cox regression.

RESULTS

There was a significant difference in CSS (P = .015) and time to hormone resistance (P = .02) among those who had first-year minimum nadir testosterone ≤ 0.7, > 0.7 to ≤ 1.7, and ≥ 1.7 nmol/L. Patients with first-year nadir testosterone consistently > 0.7 nmol/L had significantly higher risks of dying as a result of disease (0.7 to 1.7 nmol/L: hazard ratio [HR], 2.08; 95% CI, 1.28 to 3.38; > 1.7 nmol/L: HR, 2.93; 95% CI, 0.70 to 12.30) and developing hormone resistance (0.7 to 1.7 nmol/L: HR, 1.62; 95% CI, 1.20 to 2.18; ≥ 1.7 nmol/L: HR, 1.90; 95% CI, 0.77 to 4.70). Maximum testosterone ≥ 1.7 nmol/L predicted for a higher risk of dying as a result of disease (P = .02).

CONCLUSION

Low nadir serum testosterone (ie, < 0.7 mmol/L) within the first year of androgen-deprivation therapy correlates with improved CSS and duration of response to androgen deprivation in men being treated for biochemical failure undergoing CAD.

Maximal testosterone suppression in prostate cancer--free vs total testosterone

Testosterone remains a key target in the treatment of advanced prostate cancer. The relationship of free testosterone to prostate cancer treatment and outcomes remains largely unexplored. A consensus of prostate cancer experts was convened in 2013 to review current knowledge surrounding relationship of total and free testosterone to prostate cancer, discuss the free hormone hypothesis, and highlight future avenues for therapeutics. Free testosterone may better reflect prostate cancer tissue androgen levels than serum total testosterone concentration. Free testosterone deserves more research regarding its relation to clinical outcomes.

Nonmetastatic castration-resistant prostate cancer

After the introduction of prostate cancer screening with the prostate-specific antigen (PSA) test, we have witnessed a dramatic stage migration. As a result, an increasing number of patients are diagnosed at earlier stages and receive local treatments including surgery or radiation. When these local treatments fail by the definition of increasing PSA levels, patients are usually treated with androgen-deprivation therapy. A fraction of these patients will finally reach a state of castration-resistant prostate cancer (CRPC) even without radiological evidence of metastasis, which is referred to as nonmetastatic CRPC (NM-CRPC). Most men with advanced or metastatic prostate cancer initially respond to various types of androgen ablation, but a considerable portion of them eventually progress to NM-CRPC. Among patients with NM-CPRC, about one-third will develop bone metastasis within 2 years. In these patients, PSA kinetics is the most powerful indicator of progression and is usually used to trigger further imaging studies and enrollment in clinical trials. Although CRPC remains largely driven by the androgen receptor, the benefit of second-line hormonal manipulations, including first-generation antiandrogens, adrenal synthesis inhibitors, and steroids, has not been investigated in men with NM-CRPC. To date, denosumab is the only agent that has been shown to delay the onset of bone metastasis. However, overall survival did not differ. In treating NM-CRPC patients, physicians should recognize the heterogeneity of the disease and acknowledge that the recently approved second-line treatments have been studied only in advanced stages of the disease.

Non-metastatic CRPC and asymptomatic metastatic CRPC: which treatment for which patient?

The introduction of early PSa-based diagnosis has profoundly impacted the epidemiology of castration-resistant prostate cancer (CRPC). Many patients enter the disease at an early stage when the only sign of resistance to androgen deprivation therapy (ADT) is a progressive elevation of prostate-specific antigen (PSA). This created a very heterogeneous population of non-metastatic (M0) CRPC. PSa kinetics is the most powerful indicator of aggressiveness in that population and can be used to trigger imaging investigation and enrollment in clinical trials. Several registered and near to come treatments have not been tested in that population but in men with more advanced metastatic and often symptomatic disease. Several agents have been investigated to delay the onset of the first bone metastasis but only one, denosumab, has reached its end-point. Because CRPC remains largely driven by the androgen receptor (AR), physicians have relied on second-line hormonal manipulations to delay the progression of the disease, including first generation antiandrogens, adrenal synthesis inhibitors, steroids and estrogens. The data however are mostly limited to phase II trials.

Experience with degarelix in the treatment of prostate cancer

Degarelix is a gonadotrophin-releasing hormone (GnRH) antagonist for the first-line treatment of androgen-dependent advanced prostate cancer. It has a direct mechanism of action that blocks the action of GnRH on the pituitary with no initial surge in gonadotrophin or testosterone levels. Degarelix is the most extensively studied and widely available GnRH antagonist worldwide. Clinical studies have demonstrated similar efficacy to the GnRH agonist leuprolide in achieving testosterone suppression in patients with prostate cancer. However, degarelix produces a faster suppression of testosterone and prostate-specific antigen (PSA), with no testosterone surge or microsurges, thus preventing the risk of clinical flare in advanced disease. Clinical trials have demonstrated that degarelix can offer improved disease control when compared with a GnRH agonist in terms of superior PSA progression-free survival (suggesting that degarelix likely delays progression to castration-resistant disease), and a more significant impact on bone serum alkaline phosphatase and follicle-stimulating hormone. Degarelix is generally well tolerated, with no reports of systemic allergic reactions in any clinical studies. In conclusion, degarelix offers clinicians a rational first-line hormonal monotherapy option for the management of advanced prostate cancer.

Androgen deprivation therapy: past, present and future

Since Huggins and Hodges demonstrated the responsiveness of prostate cancer to androgen deprivation therapy (ADT), androgen-suppressing strategies have formed the cornerstone of management of advanced prostate cancer. Approaches to ADT have included orchidectomy, oestrogens, luteinizing hormone-releasing hormone (LHRH) agonists, anti-androgens and more recently the gonadotrophin-releasing hormone antagonists. The most extensively studied antagonist, degarelix, avoids the testosterone surge and clinical flare associated with LHRH agonists, offering more rapid PSA and testosterone suppression, improved testosterone control and improved PSA progression-free survival compared with agonists. The clinical profile of degarelix appears to make it a particularly suitable therapeutic option for certain subgroups of patients, including those with metastatic disease, high baseline PSA (>20 ng/mL) and highly symptomatic disease. As well as forming the mainstay of treatment for advanced prostate cancer, ADT is increasingly used in earlier disease stages. While data from clinical trials support the use of ADT neoadjuvant/adjuvant to radiotherapy for locally advanced or high-risk localized prostate cancer, it remains to be established whether specific ADT classes/agents provide particular benefits in this clinical setting.

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.

Incomplete testosterone suppression with luteinizing hormone-releasing hormone agonists: does it happen and does it matter?

What's known on the subject? and What does the study add? Previous reports, with small numbers of patients, have described the problem of incomplete testosterone suppression (>1.1 or 1.7 nmol/L) with LHRH agonists. Various predisposing factors have been suggested: different drug agents and patient factors such as age, pretreatment testosterone levels and weight. Such incomplete testosterone suppression has been shown in one small report to be associated with increased PSA failure rates and in another report in those with metastases, with worse survival. This study used testosterone assays that are more accurate at low levels than those used in most previous reports in a large dataset of 2196 men, and confirmed incomplete testosterone suppression (breakthrough) rates >1.7 nmol/L of 3.4% and >1.1 nmol/L of 6.6%. We showed that younger age was strongly associated with the risk of breakthrough, with a minor effect of increasing body mass index. Repeated breakthroughs were more common (16%) in those who had already had one breakthrough. Interim measures of cancer control (PSA kinetics during LHRH therapy) were inferior in those with a breakthrough, and those with breakthroughs between 1.1 and 1.7 nmol/L had worse long-term biochemical control rates.

OBJECTIVES

• To describe breakthrough rates above castrate levels of testosterone, in a population-based series of men undergoing adjuvant luteinizing hormone-releasing hormone (LHRH) agonist therapy with curative radiation therapy. • To explore the predisposing factors for such breakthroughs and their impact on subsequent outcomes.

PATIENTS AND METHODS

• All men treated for prostate cancer between 1998 and 2007 with curative radiation in the province of British Columbia, Canada were potentially eligible (n= 11752). Of these, 2196 fulfilled the eligibility criteria. • Serial testosterone measurements were obtained during continuous LHRH therapy. • Breakthrough rates >1.1 nmol/L and >1.7 nmol/L were calculated for each LHRH injection and for each patient course. • Predisposing factors were identified, and early surrogates of oncological outcome (neoadjuvant nadir and post-treatment nadir) were determined.

RESULTS

• The risk of a breakthrough >1.1 nmol/L was 6.6%, and >1.7 nmol/L was 3.4% per patient course and 5.4% and 2.2% per LHRH injection (inclusive ranges). • Repeated breakthroughs occurred in 16% of patients. • Younger men were more liable to breakthroughs (P < 0.001). • Early PSA kinetic surrogates of cancer control were inferior in those with breakthroughs. • Neither overall biochemical non-evidence of disease (bNED) nor survival were compromised, although subgroup analysis showed inferior 5-year bNED in those with breakthroughs of 1.1-1.7 nmol/L vs those without (58% vs 73%, respectively; P= 0.048).

CONCLUSIONS

• Breakthroughs with LHRH agonists occur occasionally per injection, but occur commonly per patient course of treatment, and adversely affect early surrogate measures of outcome. • The monitoring of testosterone levels during therapy is therefore advised.

Testosterone in prostate cancer: the Bethesda consensus

OBJECTIVE

• Androgen stimulation of prostate cancer (PCa) cells has been extensively studied. The increasing trend of using serum testosterone as an absolute surrogate for castration state means that the diagnostic measurement of testosterone and the values potentially influencing prognosis must be better understood. This is especially important when PCa progresses from an endocrine to an intracrine status.

PATIENTS AND METHODS

• We performed a literature review using the MEDLINE database for publications on: (i) hormonal changes with androgen deprivation therapy (ADT); (ii) monitoring hormonal therapy with testosterone measurement; (iii) the efficacy of intermittent androgen deprivation (IAD) compared with continuous androgen deprivation; (iv) the underlying mechanisms of castration-resistance; and (v) novel treatments for castration-resistant PCa (CRPCa).

RESULTS

• The optimum serum castration levels to be achieved with ADT are still debated. Recently, the 50 ng/dL threshold has been questioned because of reports indicating worse outcomes when levels between 20 and 50 ng/dL were studied. Instead, a 20 ng/dL threshold for serum testosterone after ADT in patients with advanced prostate cancer was recommended.

CONCLUSION

• Understanding the mechanisms of androgen biosynthesis relating to PCa as well as prognostic implications might achieve a consensus regarding the role of ADT for both the androgen-sensitive and -insensitive disease state.