Variations of serum testosterone levels in prostate cancer patients under LH-releasing hormone therapy: an open question

Evaluation of maintenance of the common androgen deprivation therapy with the new antiandrogen therapy in patients with castration-resistant prostate cancer: a systematic review

PURPOSE

Advanced prostate cancer does not respond to traditional androgen deprivation therapy (ADT) at some point in the treatment. The development of new hormonal agents demonstrated clear efficacy and changed the treatment scenario.

OBJECTIVES

To evaluate the use of new antiandrogens alone versus their use in combination with maintenance ADT in patients with advanced castration-resistant prostate cancer.

METHODS

A literature systematic review of randomized clinical trials, cohorts, and real-life studies including patients who received the new antiandrogens with or without ADT due to histologic confirmed advanced castration-resistant prostate adenocarcinoma was carried out.

RESULTS

2181 articles were identified and three studies were included with a total of 246 patients. Two studies were randomized clinical trials, and the third was a retrospective study, which showed similar results for both arms, in relation to PSA response, radiological progression-free survival, and testosterone levels, in addition to cost analysis with savings avoided in the ADT maintenance-free arm. Despite the positive data, it is still not possible to categorically state whether there is a statistical benefit in suspending the ADT during the use of new antiandrogens, due to the heterogeneity of the studies.

CONCLUSION

The literature is limited on the issue. Available data are still immature with no clear benefit of the use of newer antiandrogens alone in the setting of advanced castration-resistant prostate cancer.

Population pharmacokinetic-pharmacodynamic modelling of the relationship between testosterone and prostate specific antigen in patients with prostate cancer during treatment with leuprorelin

AIMS

This investigation aimed to quantitatively characterize the relationship between the gonadotropin-releasing hormone agonist leuprorelin, testosterone (T) and prostate specific antigen (PSA) concentrations over time, to aid identification of a target T concentration that optimises the balance of the benefits of T suppression whilst reducing the risk of side effects related to futile over-suppression.

METHODS

Data from a single dose study to investigate the effect of leuprorelin in a 6-month depot formulation on T and PSA in prostate cancer patients were analysed using a population pharmacokinetic-pharmacodynamic modelling approach. The developed model was qualified using external data from 3 studies, in which the effect of different formulations of leuprorelin on T and PSA was evaluated in prostate cancer patients.

RESULTS

The effect of leuprorelin on the relationship between T and PSA was adequately characterized by the Romero model with minor modifications, combined with a turnover model to describe the delay in response between T and PSA. The data were significantly better described when assuming a minimum PSA level that is independent on the treatment-related reduction in T, as compared to a model with a proportional reduction in PSA and T.

CONCLUSIONS

The model-based analysis suggests that on a population level, reducing T concentrations below 35 ng/dL does not result in a further decrease in PSA levels (>95% of the minimal PSA level is reached). More data are required to support this relationship in the lower T and PSA range.

Nanomedicine for prostate cancer using nanoemulsion: A review

Prostate cancer (PCa) is a worldwide issue, with burgeoning rise in prevalence, morbidity and mortality. Targeted drug delivery, a long sort solution in this regard using controlled release (CR) - nanocarriers, is still a challenge. There is an emerging criticism that, the challenges are due to less appreciation for the biological barriers and lack of corresponding newer technologies. Over the years, more understanding about the biological barriers has come with the progress in characterization techniques. Correspondingly, there is a change in opinion about approaches in clinical trial that; focus of the end point need to be shifted towards disease stabilization for these explorative technologies. Currently, there is a requirement to overcome these newly identified challenges to develop newer affordable therapeutics. The ongoing clinical protocol for therapy using CR-nanocarriers is intravenous injection followed by local targeting to cancer site. This is the most accepted protocol and new CR-nanocarriers are being developed to suit this protocol. In this review, recent progress in treatment of PCa using CR-nanocarriers is analyzed with respect to newly identified biological barriers and design challenges. Possibilities of exploring nanoemulsion (NE) platform for targeted drug delivery to PCa are examined. Repurposing of drugs and combination therapy using NE platform targeted to PCa can be explored for design and development of affordable nanomedicine. In 20yrs. from now there expected to be numerous affordable nanomedicine technologies available in market exploring these lines.

Steroid Hormone Receptors as Potential Mediators of the Clinical Effects of Dutasteride: A Prospective, Randomized, Double-Blind Study

This study characterizes the clinical and morphofunctional effects of a 5α-reductase inhibitor on steroid hormone receptors in normal human prostate tissue, as potential mediators of the clinical effects of dutasteride. This work was a prospective, double-blind, and randomized study that evaluated 49 men aged between 45 and 70 years, with no alterations in a digital rectal examination and prostate-specific antigen measurements between 2.5 and 4.0 ng/mL. These patients underwent prostate biopsy guided by transretal ultrasound with prostate neoplasia being ruled out, and the patients were divided into two groups, with one group receiving dutasteride ( n = 25) and one group receiving a placebo ( n = 24). The patients were clinically assessed each quarter, and at the end of 12 months they underwent new laboratory tests, prostate rebiopsy, and histopathological, immunohistochemical and clinical analyses. The estrogen receptor-beta (ERβ) and androgen receptor immunoreactivities were higher, and the proliferation/apoptotic ratio was significantly lower with predominance of the apoptotic process, followed by a significant reduction in the prostate volume and the total serum prostate-specific antigen levels in the dutasteride group when compared with the placebo group, with a clear supremacy of ERβ. There were no significant variations in the serum estrogen and testosterone levels, in the body mass index, or in the ERα immunoreactivities in the dutasteride and placebo groups. The results demonstrated the importance of the ERβ pathway in the activation mechanisms of apoptosis, exerting a protective effect in the normal prostate, indicating that this receptor might be an important mediator of the clinical effects of dutasteride.

Extended release, 6-month formulations of leuprolide acetate for the treatment of advanced prostate cancer: achieving testosterone levels below 20 ng/dl

INTRODUCTION

Luteinizing hormone-releasing hormone agonists such as leuprolide acetate (LA) are the most frequently utilized treatment of advanced prostate cancer as the regimen for achieving androgen deprivation therapy (ADT). The efficacy of LA is determined by extent of testosterone (T) suppression in prostate cancer patients. Although, the historical castrate T suppression target has been defined as < 50 ng/dl, this level may not be as low as required to deliver equivalent suppression as achieved by surgical castration. Recent studies have demonstrated that a T level as low as 20 ng/dl may produce improved clinical outcomes.

AREAS COVERED

LA is available in long-acting formulations that deliver active drug over the course of 1-6 months from a single-dose administration. The technologies utilized to provide sustained drug delivery differ: one mode of administration uses microspheres, which encapsulate the drug and are injected as a suspension intramuscularly; another mode of administration uses a liquid polymer that creates a single, solid depot after injection subcutaneously. This article will review the safety and efficacy of both 6-month LA formulations, as well as their impact in prostate cancer treatment.

EXPERT OPINION

As the understanding of optimal T castrate level evolves and may be refined pending new data from contemporaneous trials, achievement and maintenance of T levels well below 50 ng/dl may be important in evaluating potential differences in ADT regimens.

Correlation Between Testosterone and PSA Kinetics in Metastatic Prostate Cancer Patients Treated With Diverse Chemical Castrations

To assess total testosterone and prostatic-specific antigen (PSA) kinetics among diverse chemical castrations, advanced-stage prostate cancer patients were randomized into three groups of 20: Group 1, Leuprolide 3.75 mg; Group 2, Leuprolide 7.5 mg; and Group 3, Goserelin 3.6 mg. All groups were treated with monthly application of the respective drugs. The patients' levels of serum total testosterone and PSA were evaluated at two time periods: before the treatment and 3 months after the treatment. Spearman's rank correlation coefficient was utilized to verify the hypothesis of linear correlation between total testosterone and PSA levels. At the beginning the patients' age, stage, grade, PSA, and total testosterone were similar within the three groups, with median age 72, 70, and 70 years in Groups 1, 2, and 3, respectively. Three months after the treatment, patients who received Leuprolide 7.5 mg presented significantly lower median total testosterone levels compared with Goserelin 3.6 mg and Leuprolide 3.75 mg (9.5 ng/dL vs. 20.0 ng/dL vs. 30.0 ng/dL, respectively; p = .0072), while those who received Goserelin 3.6 mg presented significantly lower PSA levels compared with Leuprolide 7.5 mg and Leuprolide 3.75 mg (0.67 vs. 1.86 vs. 2.57, respectively; p = .0067). There was no linear correlation between total testosterone and PSA levels. Overall, regarding castration levels of total testosterone, 28.77% of patients did not obtain levels ≤50 ng/dL and 47.80% did not obtain levels ≤20 ng/dL. There was no correlation between total testosterone and PSA kinetics and no equivalence among different pharmacological castrations.

Selective estrogen receptor alpha agonist GTx-758 decreases testosterone with reduced side effects of androgen deprivation therapy in men with advanced prostate cancer

BACKGROUND

A need remains for new therapeutic approaches for men with advanced prostate cancer, particularly earlier in the disease course.

OBJECTIVE

To assess the ability of an oral selective estrogen receptor α agonist (GTx-758) to lower testosterone concentrations compared with leuprolide while minimizing estrogen deficiency-related side effects of androgen-deprivation therapy.

DESIGN, SETTING, AND PARTICIPANTS

Hormone-naive advanced prostate cancer patients were randomized to oral GTx-758 1000 mg/d, 2000 mg/d, or leuprolide depot.

INTERVENTION

GTx-758 and leuprolide.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary end point was the proportion of patients achieving total testosterone ≤ 50 ng/dl by day 60. Secondary end points included serum free testosterone, prostate-specific antigen (PSA), sex hormone-binding globulin, hot flashes, bone turnover markers, and insulin-like growth factor (IGF)-1 levels.

RESULTS AND LIMITATIONS

Of 159 randomized patients, leuprolide reduced total testosterone to ≤ 50 ng/dl in a greater proportion of patients than GTx-758 by day 60 (43.4%, 63.6%, and 88.2% of subjects receiving GTx-758 1000 mg [p<0.001], GTx-758 2000 mg [p=0.004], and leuprolide, respectively). GTx-758 reduced free testosterone and PSA earlier and to a greater degree than leuprolide. GTx-758 led to fewer hot flashes, decreases in bone turnover markers, and alterations in IGF-1 compared with leuprolide. A higher incidence of venous thromboembolic events (VTEs) was seen with GTx-758 (4.1%) compared with leuprolide (0.0%).

CONCLUSIONS

Although leuprolide reduced total testosterone to ≤ 50 ng/dl in a greater proportion of patients compared with GTx-758, GTx-758 was superior in lowering free testosterone and PSA. GTx-758 reduced estrogen deficiency side effects of hot flashes, bone loss, and insulin resistance but with a higher incidence of VTEs.

PATIENT SUMMARY

This paper reports findings that leuprolide lowered total testosterone more than GTx-758 but that GTx-758 lowered free testosterone and prostate-specific antigen more than leuprolide. GTx-758 also reduced estrogen deficiency side effects, albeit at a higher rate of vascular events.

TRIAL REGISTRATION

Clinicaltrials.gov identifier NCT01615120.

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.

Effects of platelet-activating factor and its differential regulation by androgens and steroid hormones in prostate cancers

Background:

Platelet-activating factor (PAF) is an arachidonic acid metabolite that plays an important role in cell proliferation, migration and neoangiogenesis, but whether it is involved in the progression of prostate cancer remains undiscovered.

Methods:

Clinical prostate specimens were investigated with immunohistochemistry method and in vitro cell experiments referred to MTS cell proliferation assay, invasion and migration experiment, quantitative real-time RT–PCR assay, western blotting analysis and ELISA assay.

Results:

Platelet-activating factor synthetase, lyso-PAF acetyl transferase (LPCAT1), increased significantly in castration-resistant prostate cancer (CRPC) specimens and CRPC PC-3 cells than that in controls. Intriguingly, PAF induced invasion and migration of PC-3 cells but not LNCaP cells. The PAF receptor antagonist inhibited proliferation of LNCaP and PC-3 cells. Dihydrotestosterone (DHT) treatment caused a decrease in LPCAT1 expression and PAF release in LNCaP cells, which could be blocked by androgen receptor antagonists. Finally, DHT increased LPCAT1 expression and PAF release in PC-3 cells in a Wnt/β-catenin-dependent manner.

Conclusion:

For the first time, our data supported that PAF might play pivotal roles in the progression of prostate cancer, which might throw a new light on the treatment of prostate cancer and the prevention of the emergence of CRPC.