Androgen receptor pathway inhibitors, prostate cancer, and older adults: a global Young International Society of Geriatric Oncology drug review

Prostate cancer is a disease of older adults that has undergone a significant therapeutic paradigm shift in the last decade with the emergence of novel androgen receptor pathway inhibitors (ARPis). One of the more commonly used ARPis is enzalutamide. This drug, along with darolutamide and apalutamide, initially received approvals in the metastatic castrate-resistant prostate cancer setting but is now utilized frequently in the metastatic castrate-sensitive and non-metastatic castration-resistant settings. Landmark phase III data illustrating ARPi efficacy in older adults are limited to those with excellent performance status. However, its role in unfit older prostate cancer patients remains to be explored in the context of a narrative review. This first-of-its-kind drug review aims to shed light on the most up-to-date evidence behind the unique toxicity profile of ARPis in the context of geriatric vulnerabilities such as cognitive and functional impairment, along with potential solutions and supporting evidence that exists to circumvent these issues in the vulnerable older adult.

The Prostate Cancer Therapy Enzalutamide Compared with Abiraterone Acetate/Prednisone Impacts Motivation for Exploration, Spatial Learning and Alters Dopaminergic Transmission in Aged Castrated Mice

Simple Summary

Cognitive side effects and fatigue after cancer treatment now constitute a major challenge in oncology. Abiraterone acetate plus prednisone (AAP) and enzalutamide (ENZ) are next-generation therapies improving metastatic castration-resistant prostate cancer (mCRPC) patient survival, but also associated with neurological disturbances. We developed a behavioral 17 months-aged and castrated mouse model receiving AAP or ENZ for 5 days per week for six weeks. We establish that ENZ impacts locomotor and explorative behaviors, and strength capacity likely by preventing binding of central synthetized androgens to androgen receptors expressed by dopamine neurons of the Substantia Nigra and the Ventral Tegmentum. ENZ also reduces the cognitive score, associated with less neuronal activity in dorsal hippocampal areas. This demonstrates ENZ-specific consequences on motivation to exploration and cognition, being of particular importance for future management of elderly prostate cancer patients and their quality of life.

Abstract

Cognitive side effects after cancer treatment threatening quality of life (QoL) constitute a major challenge in oncology. Abiraterone acetate plus prednisone (AAP) and enzalutamide (ENZ) are examples of next-generation therapy (NGT) administered to metastatic castration-resistant prostate cancer (mCRPC) patients. NGT significantly improved mCRPC overall survival but neurological side effects such as fatigue and cognitive impairment were reported. We developed a behavioral 17 months-aged and castrated mouse model receiving per os AAP or ENZ for 5 days per week for six consecutive weeks. ENZ exposure reduced spontaneous activity and exploratory behavior associated with a decreased tyrosine hydroxylase (TH)-dopaminergic activity in the substantia nigra pars compacta and the ventral tegmental area. A decrease in TH⁺-DA afferent fibers and Phospho-DARPP32-related dopaminergic neuronal activities in the striatum and the ventral hippocampus highlighted ENZ-induced dopaminergic regulation within the nigrostriatal and mesolimbocortical pathways. ENZ and AAP treatments did not substantially modify spatial learning and memory performances, but ENZ led to a thygmotaxis behavior impacting the cognitive score, and reduced c-fos-related activity of NeuN⁺-neurons in the dorsal hippocampus. The consequences of the mCRPC treatment ENZ on aged castrated mouse motivation to exploration and cognition should make reconsider management strategy of elderly prostate cancer patients.

Real-World Data on Outcomes in Metastatic Castrate-Resistant Prostate Cancer Patients Treated With Abiraterone or Enzalutamide: A Regional Experience

BACKGROUND

Both abiraterone and enzalutamide have shown to improve overall survival (OS), progression-free survival (PFS) and prostate-specific antigen (PSA) response in patients with metastatic castration-resistant prostate cancer (mCRPC) regardless of previous treatment with chemotherapy (COU-AA3011, COU-AA3022, AFFIRM3 and PREVAIL4). The data regarding the impact of these treatments in the real world setting is scarce. This study assessed the real world survival and disease outcomes in mCRPC patients in a regional health service in Victoria with the use of abiraterone and enzalutamide.

METHODS

This retrospective clinical audit included 75 patients with diagnosis of mCRPC treated with either abiraterone or enzalutamide between January 1, 2014, and December 31, 2019, at Goulburn Valley Health. Patients were stratified according to the drug received, Eastern Cooperative Oncology Group (ECOG) performance status, Gleason score, burden of disease at diagnosis, presence of visceral metastases and use of previous chemotherapy. The primary end point was PSA response (defined as a reduction in the PSA level from baseline by 50% or more). The secondary outcomes were PSA PFS, radiographic PFS, and OS.

RESULTS

Thirty-seven patients received enzalutamide, and the other 38 received abiraterone. Only 20% of patients in either group had visceral metastases. 32% of patients receiving enzalutamide had a high burden of disease, compared to 53% receiving abiraterone. 38% of patients in the enzalutamide group and 53% in the abiraterone group had received prior chemotherapy. PSA response rates were higher in the enzalutamide group than abiraterone group (70.3% vs 37.8%). Both PSA and radiographic PFS were longer in the enzalutamide group than abiraterone group; 7 months vs 5 months for both end points. OS was also found to be longer in patients receiving enzalutamide; 30 months compared to only 13 months in patients receiving abiraterone.

CONCLUSION

Both abiraterone and enzalutamide have shown to result in significant PSA response rates, as well as PFS and OS benefit in mCRPC patients in the real world setting. The difference in responses and survival benefit are probably impacted by the unbalanced burden of disease.

Medication patterns of abiraterone acetate plus prednisone or enzalutamide and PSA progression in veterans with metastatic castration-resistant prostate cancer

OBJECTIVES

To quantify the association between dose reductions of abiraterone acetate plus prednisone (AAP) or enzalutamide and prostate-specific antigen (PSA) progression in patients with metastatic castration-resistant prostate cancer (mCRPC). Changes in medication-taking patterns of AAP or enzalutamide may arise due to clinical (e.g. toxicity) and non-clinical (e.g. patient compliance) reasons in men with mCRPC. However, it is unclear how this affects PSA progression.

METHODS

Veterans Health Administration electronic health record database was used to identify Veterans diagnosed with prostate cancer who initiated AAP or enzalutamide (index) from April 2010 to December 2016. PSA progression was defined as the first rise in PSA of ≥2 ng/mL and ≥25% above nadir. The relative dose intensity (RDI) was defined as the ratio of the total dispensed dose over the last two months to the standard recommended dose and was updated monthly. Dose reduction was assessed using a threshold of RDI < 80%.

RESULTS

The cohort included 6069 Veterans aged 74.6 years on average. Mean follow-up was 12.3 months. PSA progression occurred in 62.7% of patients. About 63.6% of AAP- and 67.2% of enzalutamide-treated patients had ≥1 occurrence of RDI <80%. RDI <80% was associated with an 8.8% higher risk of PSA progression (hazard ratio [HR] = 1.088; p = .019; 95% confidence interval [CI] [1.014; 1.166]).

CONCLUSIONS

Dose reduction was observed in most patients and was associated with significantly higher risk of PSA progression in men with mCRPC. These results suggest future efforts to minimize dose reductions for non-clinical reasons are warranted and that patient adherence should be encouraged to limit the risk of PSA progression.

Optimizing outcomes for patients with metastatic prostate cancer: insights from South East Asia Expert Panel

AIMS

Clinical decision making is challenging in men with metastatic prostate cancer (mPC), as heterogeneity in treatment options and patient characteristics have resulted in multiple scenarios with little or no evidence. The South East Asia Expert Panel 2019 addressed some of these challenges.

METHODS

Based on evidence in the literature and expert interviews, 19 statements were formulated for key challenges in the treatment of men with castration-sensitive and -resistant prostate cancer in clinical practice. A modified Delphi process was used to reach consensus among experts in the panel and develop clinical practice recommendations.

RESULTS

The majority of the panel preferred a risk-based stratification and recommended abiraterone or enzalutamide as first-line therapy for symptomatic chemotherapy naïve patients. Abiraterone is preferred over enzalutamide as a first-line treatment in these patients. However, the panel did not support the use of abiraterone in high risk lymph-node positive only (N+M0) or in non-metastatic (N0M0) patients. In select patients, low dose abiraterone with food may be used to optimize clinical outcomes. Androgen receptor gene splice variant status may be a useful guide to therapy. In addition, generic versions of approved therapies may improve access to treatment to a broader patient population. The choice of treatment, as well as sequencing are guided by both patient and disease characteristics, preferences, drug access, cost, and compliance.

CONCLUSION

Expert recommendations are key to guidance for the optimal management of mPC. Appropriate choice, timing, and sequence of treatment options can help to tailor therapy to maximize outcomes in men with mPC.

Comparing the clinical efficacy and safety of abiraterone and enzalutamide in metastatic castration-resistant prostate cancer: A systematic review and meta-analysis

BACKGROUND

Two new drugs, abiraterone and enzalutamide, had recently shown beneficial effects on survival in patients with metastatic castration-resistant prostate cancer. We systematically reviewed the efficacy and safety of abiraterone and enzalutamide in metastatic castration-resistant prostate cancer in real-world practice.

METHODS

A search from PubMed, Web of Science, Cochrane, Embase was conducted up to 6 March 2019. Available articles from conferences were searched. The endpoint was prostate-specific antigen response, overall survival, progression-free survival, number of patients with any adverse event.

RESULTS

Fourteen cohort studies involving 3469 participants were included. Pooled result showed that prostate-specific antigen response was higher for patients receiving enzalutamide than abiraterone (790 patients, odds ratio (OR) 0.47, 95% confidence interval (CI) 0.29-0.77, P = 0.003, I²=59%). Enzalutamide was significantly associated with increased adverse events rate in comparison with abiraterone (730 patients, OR 0.35, 95%CI 0.13-0.92, P = 0.03, I²=65%). There was no statistical difference between abiraterone and enzalutamide with respect to perceived cognitive impairments (1856 patients, OR 0.90, 95%CI 0.29-2.76, P = 0.85, I²=5%). Enzalutamide was significantly associated with increased fatigue risk in comparison with abiraterone (2477 patients, OR 0.46, 95%CI 0.34-0.63, P＜0.00001, I²=0%).

CONCLUSIONS

Our results demonstrated that enzalutamide was more efficacious than abiraterone for patients with metastatic castration-resistant prostate cancer, but was associated with a significantly elevated risk of side effects, particularly fatigue.

A review of prostate cancer treatment impact on the CNS and cognitive function

BACKGROUND

Androgen deprivation therapy (ADT) is the backbone of systemic therapy for men with prostate cancer (PC); almost one-half of patients receive treatment during their disease course. However, a range of cognitive and other central nervous system (CNS) changes have been associated with ADT. In this review, we discuss extant data describing these complications and the mechanisms through which medications used to deliver ADT may affect them.

METHODS

We performed a MEDLINE search for appropriate papers published between January 2000 and December 2018. Relevant papers were selected and reviewed; additional publications were identified by manually assessing references from included papers, and recent congress abstracts.

RESULTS

Of ~230 search outputs, 33 were selected for inclusion. Some studies suggested a clear association between ADT and CNS effects in men with PC, whereas others did not. Accurate assessment is limited by test instrument variability, inadequate sample sizes, short follow-up duration, and limited prospective longitudinal studies. The approved second-generation androgen receptor (AR) inhibitors enzalutamide and apalutamide were associated with some CNS-related adverse events (AEs) in clinical studies, including fatigue (which can interfere with cognitive function). The androgen synthesis inhibitor abiraterone acetate was associated with a low CNS AE profile when compared with enzalutamide. The AR antagonist darolutamide demonstrated a comparable incidence of cognitive disorder in clinical trials to that of ADT alone.

CONCLUSIONS

Adequately caring for men receiving ADT requires an understanding of the symptoms, incidence and magnitude of cognitive effects, and a feasible approach to cognitive assessment and management in clinical settings. Some CNS effects could relate to blood-brain barrier penetration and direct AR inhibitor activity; drug safety profiles may differ by the degree of blood-brain barrier penetration of particular agents. Ongoing clinical trials seek to define the CNS tolerability of newer AR pathway-targeted therapy options more clearly.