Initial dose reduction of enzalutamide does not decrease the incidence of adverse events in castration-resistant prostate cancer

Real-world prostate-specific antigen response and progression to castration-resistant prostate cancer among men with metastatic castration-sensitive prostate cancer treated with apalutamide: a multi-institutional study in the Chu-shikoku Japan Urological Consortium

BACKGROUND

Japanese men receiving apalutamide often experience skin-adverse events (AEs), possibly requiring treatment interruption or dose reduction. However, concerns have arisen regarding the impact of these adjustments on the efficacy of apalutamide. Our study evaluated the efficacy, safety, and persistence of apalutamide in men with metastatic castration-sensitive prostate cancer (mCSPC).

METHODS

We retrospectively reviewed the medical records of 108 men with mCSPC from 14 Japanese institutions. The primary outcomes were the efficacy of apalutamide: prostate-specific antigen (PSA) response (50%, 90% and < 0.2 decline) and progression to castration-resistant prostate cancer (CRPC). The secondary outcomes were the skin-AE and compliance of apalutamide.

RESULTS

PSA50%, PSA90% and PSA < 0.2 declines were observed in 89.8, 84.3 and 65.7%, and the median time to CRPC progression was not reached. PSA < 0.2 decline and an initial full dose of apalutamide were significantly associated with a longer time to CRPC. The most common AE was skin-AE (50.9%), and there was no association between the occurrence of skin-AE and the time to CRPC (P = 0.72). The median apalutamide persistence was 29 months, which was longer in the initial full dose recipients than in the reduced dose recipients. The dosage is reduced in about 60% of patients within the first year of treatment in the initial full dose recipients.

CONCLUSIONS

Our findings indicate the effectiveness of apalutamide in Japanese men with mCSPC, despite a substantial portion requiring dose reduction within a year among the initial full dose recipients.

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.

Low-Dose Enzalutamide in Metastatic Prostate Cancer-Longevity Over Conventional Survival Analysis

BACKGROUND

Enzalutamide is an important drug in the treatment of prostate cancer. Standard dosing often requires dose reduction because of side effects. There is no information on survival outcomes with lower doses. We investigated the impact of starting enzalutamide at ≤ 50% dose on metastatic prostate cancer outcomes including patients' longevity.

PATIENTS AND METHODS

Records of metastatic prostate cancer patients treated with enzalutamide at one center were retrospectively reviewed. Low-dose enzalutamide (≤80 mg/day) was compared with standard-dose (160 mg/day). The primary objective was to compute the restricted mean survival time (RMST - time scale) and restricted mean attained age (RMAA - age scale) using the Irwin method. Secondary objectives included overall survival (OS), progression-free survival (PFS), and PSA progression per PCWG3 criteria (PSA PFS). We used the logrank test and the ∆ difference between RMSTs for comparison.

RESULTS

Of 111 patients treated, 32 received a low-dose and 79 the standard-dose. Low-dose patients had less prior abiraterone or chemotherapy (28.1% vs. 65.8%, P < .001); more testosterone assessment (65.6% vs. 40.5%, P = .016); poorer ECOG performance status (48.3% score ≥2 vs. 26.6%; P = .040), more comorbidities (75.9% vs. 46.3%; P = .010)) including increased cardiovascular disease (51.7% vs. 21.4%, P = .004). Baseline PSA value and doubling time at start of enzalutamide and distribution of metastases were similar between the groups. OS and PFS did not differ between low-dose and standard-dose. Patients on low-dose had a better longevity with significantly longer RMAA, 89.1 years, versus standard-dose RMAA of 83.8 years (∆ = 5.3 years, P = .003, logrank P = .025). In a subgroup analysis by age at start of enzalutamide, <75 versus ≥75 years old, longevity was also better with low-dose in younger patients (∆ = 2.9 years, P = .034, and older, ∆ = 3.3 years, P = .011).

CONCLUSION

The longevity advantage and reduced adverse events seen in patients with prostate cancer treated with low-dose enzalutamide warrants further investigation.

Functional impact of androgen‐targeted therapy on patients with castration‐resistant prostate cancer

Context

Second‐generation androgen receptor inhibitors (ARIs) extend metastasis‐free survival, prolong overall survival, and delay symptoms when added to androgen deprivation therapy for the treatment of castration‐sensitive or castration‐resistant prostate cancer (CRPC). However, ARIs may adversely impact physical and cognitive function, thereby decreasing quality of life and prognosis.

Objective

To evaluate the evidence regarding the potential effects of ARIs on physical and cognitive function and to contextualize how drug‐related adverse effects may influence treatment decisions in CRPC.

Evidence acquisition

We performed a literature search using MEDLINE from January 1998 to June 2020 using terms relating to prostate cancer, androgen deprivation, and physical and cognitive function. We selected 61 publications for analysis.

Evidence synthesis

Treatment‐induced deterioration in physical and cognitive function may impair the independence and well‐being of patients with CRPC. Patient‐reported outcomes from clinical trials of ARIs provide quantitative evidence of their impact on these domains, which appears to vary between ARIs, reflecting the different adverse event profiles of these agents. Thus, the risk of physical or cognitive dysfunction may be managed or mitigated by appropriate selection of treatment options. Studies in patients with CRPC have assessed the cognitive effects of ARIs with validated instruments, whereas quantitative analysis of the impact on physical function has been limited.

Conclusion

Several validated instruments utilized for the assessment of physical and cognitive function in clinical studies have been adapted for clinical practice; however, consensus on the standardization of these assessments is required. Future clinical studies employing validated tools may generate data on the impact of ARIs and guide treatment decisions for patients with CRPC.

Patient summary

We review the hormonal therapies used to treat men with prostate cancer and the effects they have on physical and cognitive function. We discuss how to measure these effects and how this may assist when choosing treatment.

Pharmacist-Urologist Collaborative Management Improves Clinical Outcomes in Patients With Castration-Resistant Prostate Cancer Receiving Enzalutamide

Background: Enzalutamide is useful for the treatment of castration-resistant prostate cancer (CRPC). Despite its usefulness, adverse events (AEs) sometimes force patients to discontinue treatment. To maximize patient care, we developed an ambulatory care pharmacy practice that allows collaboration between a pharmacist and urologist to manage patients with CRPC receiving enzalutamide. In this study, we investigated the efficacy of this collaborative management.

Methods: A retrospective chart review of 103 patients with CRPC receiving enzalutamide in our hospital between May 2014 and December 2020 was performed. Our collaborative management was implemented in October 2016. Before being examined by urologists, patients visited the oncology pharmacy consultation room for a face-to-face consultation, wherein the oncology pharmacists assessed factors such as adherence to enzalutamide, any AEs and their grades, and provided their suggestions to the urologists. The time to enzalutamide discontinuation and prostate-specific antigen progression were compared between patients who started enzalutamide before (n = 41) and after (n = 62) the implementation of the collaborative management. A multivariate Cox regression analysis was performed to analyze the factors associated with enzalutamide discontinuation.

Results: After implementing collaborative management, the pharmacists had 881 patient consultations. Among the 476 suggestions from pharmacists, 345 were accepted by urologists. The most frequent suggestion was supportive care in enzalutamide treatment (224 suggestions). Multivariate analysis showed that collaborative management [hazard ratio (HR) 0.53, 95% confidence interval (CI) 0.31–0.89, p = 0.017] and higher prostate-specific antigen (PSA; HR 2.41, 95% CI 1.36–4.28, p = 0.003) were significantly associated with enzalutamide discontinuation. The median time to discontinuation (18.9 vs. 7.6 months, p = 0.012), time to discontinuation due to AEs (not reached in both groups, p = 0.001), and time to PSA progression (13.3 vs. 5.8 months, p = 0.002) were all significantly longer in the after group.

Conclusions: We implemented a pharmacist-urologist collaborative management program for outpatients with CRPC receiving enzalutamide. The results revealed that collaborative management was useful for prolonging the time to enzalutamide discontinuation.