Factors predicting efficacy and adverse effects of enzalutamide in Japanese patients with castration-resistant prostate cancer: results of retrospective multi-institutional study

Liver Microenvironment Response to Prostate Cancer Metastasis and Hormonal Therapy

Prostate cancer-associated deaths arise from disease progression and metastasis. Metastasis to the liver is associated with the worst clinical outcomes for prostate cancer patients, and these metastatic tumors can be particularly resistant to the currently widely used chemotherapy and hormonal therapies, such as anti-androgens which block androgen synthesis or directly target the androgen receptor. The incidence of liver metastases is reportedly increasing, with a potential correlation with use of anti-androgen therapies. A key player in prostate cancer progression and therapeutic response is the microenvironment of the tumor(s). This is a dynamic and adaptive collection of cells and proteins, which impart signals and stimuli that can alter biological processes within prostate cancer cells. Investigation in the prostate primary site has demonstrated that cells of the microenvironment are also responsive to hormones and hormonal therapies. In this review, we collate information about what happens when cancer moves to the liver: the types of prostate cancer cells that metastasize there, the response of resident mesenchymal cells of the liver, and how the interactions between the cancer cells and the microenvironment may be altered by hormonal therapy.

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.

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.

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

Background

There was no clear evidence whether the initial dose of enzalutamide affects the incidence of adverse events (AEs), and oncological outcome in patients with castration-resistant prostate cancer (CRPC).

Methods

The clinical charts of 233 patients with CRPC treated with enzalutamide were reviewed retrospectively. After 1:3 propensity score matching (PSM), 124 patients were divided into a reduced dose group and a standard dose group, and the prostate specific antigen (PSA) response and the incidence of AEs were compared.

Results

190 patients with CRPC initiated with standard dose enzalutamide were younger and better performance status compared with 43 patients beginning with reduced dose. After PSM, the baseline characteristics were not different between the standard and the reduced dose group. In the PSM cohort, the PSA response rate was significantly lower in the reduced dose group than in the standard dose group (-66.3% and -87.4%, p = 0.02). The incidence rates of AEs were not statistically different between the groups (22.6% and 34.4%, respectively, p = 0.24).

Conclusion

Initiating treatment with a reduced dose of enzalutamide did not significantly decrease the incidence rate of AEs, and it showed poorer PSA response rate. There is no clear rationale for treating with a reduced initial dose of enzalutamide to reduce the incidence of AEs.

Can 68Ga-PSMA PET/CT-derived prostate-specific membrane antigen expression parameters predict prostate-specific antigen response to enzalutamide treatment?

OBJECTIVE

In patients with metastatic castration-resistant prostate cancer (mCRPCa), enzalutamide is administered when docetaxel treatment fails. The purpose of the study was to evaluate the relationship between prostate-specific antigen (PSA) response and metabolic parameters obtained from 68Ga-PSMA PET/CT before treatment in this patient group.

METHODS

From February 2018 to May 2020, 34 patients with mCRPCa were enrolled in this study. The association between PSA response (at least 50% decrease compared to the pretreatment value) and quantitative prostate-specific membrane antigen (PSMA) expression parameters such as SUVmax, SUVmean, PSMA-TV (PSMA receptor-expressing tumor volume) and TL-PSMA (total lesion PSMA receptor expression) were evaluated.

RESULTS

Mean SUVmax, SUVmean, PSMA receptor-expressing tumor volume (PSMA-TV) and total lesion PSMA receptor expression (TL-PSMA) values were 33.66 ± 20.42; 8.82 ± 5.03; 319.85 ± 615.12 cm3; and 2894.76 ± 5195.13, respectively. In the posttreatment 12th week, 22 patients (64.7%) had PSA response, while 12 patients (35.3%) were nonresponders. In patients with PSA response, PSMA-TV values were significantly lower than nonresponders (78.37 ± 80.99 cm3 vs. 451.58 ± 734.61 cm3; P = 0.028). But there was no significant difference between responders and nonresponders in terms of age, ISUP grade, SUVmax, SUVmean, TL-PSMA, pretreatment PSA values, presence of local recurrence or metastases at any site.

CONCLUSION

PSMA-TV values on 68Ga-PSMA PET/CT imaging before starting enzalutamide treatment following docetaxel failure can predict PSA response in patients with mCRPCa.

Prognostic significance of complete blood count parameters in castration-resistant prostate cancer patients treated with androgen receptor pathway inhibitors

BACKGROUND

This study investigated the prognostic significance of complete blood count data in castration-resistant prostate cancer patients treated using androgen receptor pathway inhibitors (ARPIs).

PATIENTS AND METHODS

Patients treated with an ARPI, abiraterone or enzalutamide, as first-line therapy for castration-resistant prostate cancer from 2014 to 2018 were included. The association between complete blood count data and prognoses including progression-free survival and overall survival (OS) was investigated.

RESULTS

High white blood cell counts (<median vs. ≥median; hazard ratio [HR], 1.82, 95% confidence interval [CI], 1.14-2.89; P = 0.012) and high neutrophil-to-lymphocyte ratios (<median vs. ≥median; HR, 1.90, 95% CI, 1.11-3.27; P = 0.020) were associated with a high risk of progression in univariate analysis. In univariate analysis, high hemoglobin (Hb) levels (<median vs. ≥median; HR, 0.41, 95% CI, 0.24-0.73; P = 0.0023) and high red cell distribution widths (<median vs. ≥median; HR, 2.41, 95% CI, 1.37-4.25; P = 0.0023) were associated with a low and a high risk of all-cause mortality, respectively. In multivariate analysis, high Hb levels (<median vs. ≥median; HR, 0.42, 95% CI, 0.22-0.79; P = 0.0076) were repeatedly associated with a low risk of all-cause mortality.

CONCLUSION

We found that white blood cell counts and neutrophil-to-lymphocyte ratios may be prognostic for progression-free survival while red cell distribution widths may be prognostic for OS. In particular, a low Hb level was a robust prognostic factor for poor OS. These findings could be useful in predicting prognosis in CRPC patients treated with ARPIs.

Safety evaluation of enzalutamide dose-escalation strategy in patients with castration-resistant prostate cancer

PURPOSE

Enzalutamide (ENZ) is an androgen receptor inhibitor used for the treatment of castration-resistant prostate cancer (CRPC). The aim of this study was to evaluate the safety of the ENZ by dose-escalation strategy in patients with CRPC.

METHODS

We retrospectively reviewed patients with CRPC who received standard ENZ (started at 160 mg) or dose-escalation ENZ (started at 80 mg followed by dose escalation) from May 2014 to June 2019 in our hospital. Safety and time to treatment failure (TTF) were evaluated. Multivariate logistic regression analysis was used to evaluate adverse events and drug discontinuation. Multivariate Cox regression analysis was used to evaluate TTF.

RESULTS

Among 107 patients, 17 patients received standard ENZ and 90 patients received dose-escalation ENZ therapy. Adverse events (any grade) were observed in 88.2% of patients in the standard group and 63.3% in the dose-escalation group (P = 0.020). Grade ≥3 adverse events were observed in 23.5% and 6.7% of the patients in the standard and dose-escalation groups, respectively, (P = 0.021). Discontinuation due to adverse events was 35.3% and 12.2% in the standard and dose-escalation groups, respectively (P = 0.070). Median TTF was 10.4 months (95% confidential interval [CI]: 2.6-31.3 months) and 18.0 months (95% CI: 11.5-22.8 months) in the standard and dose-escalation groups, respectively (Hazard ratio: 0.60, 95% CI: 0.29-1.30, P = 0.194).

CONCLUSIONS

With the ENZ dose-escalation strategy, adverse events related to ENZ of any grade and grade ≥3 were significantly decreased, and discontinuation due to adverse events also decreased. Therefore, the dose-escalation strategy could be useful in optimizing the dose of ENZ.

Impact of antiandrogen withdrawal syndrome in castration-resistant prostate cancer patients treated with abiraterone or enzalutamide

OBJECTIVES

To assess the impact of antiandrogen withdrawal syndrome after bicalutamide withdrawal in castration-resistant prostate cancer patients treated with androgen receptor-axis targeted agents.

METHODS

The study cohort comprised 94 patients treated with abiraterone (n = 34) or enzalutamide (n = 60) as a first-line androgen receptor-axis targeted agent for castration-resistant prostate cancer despite combined androgen blockade by castration with bicalutamide as the first-line therapy. The association between clinicopathological factors (including antiandrogen withdrawal syndrome) and therapeutic outcome after using abiraterone and enzalutamide was investigated.

RESULTS

The decline in the prostate-specific antigen level after use of abiraterone or enzalutamide was comparable between patients with and without antiandrogen withdrawal syndrome. Antiandrogen withdrawal syndrome (hazard ratio 3.84, 95% confidence interval 1.29-11.45; P = 0.016) was associated with a higher risk of progression on multivariate analysis, but not all-cause death after abiraterone use. Progression-free survival and overall survival after enzalutamide use did not differ between patients with and without antiandrogen withdrawal syndrome.

CONCLUSIONS

The present data suggest a modest therapeutic efficacy of abiraterone in castration-resistant prostate cancer patients with anti-androgen withdrawal syndrome after bicalutamide withdrawal.

Second-line Hormonal Therapy for the Management of Metastatic Castration-resistant Prostate Cancer: a Real-World Data Study Using a Claims Database

We evaluated the efficacy of second-line hormonal therapy for treatment of metastatic castration-resistant prostate cancer (mCRPC) in a real-world retrospective study. We conducted a population-based real-world cohort study of 258 mCRPC patients between 2014 and 2018 using the Chang Gung Research Database (CGRD) of Taiwan. The second-line hormonal therapy included abiraterone acetate and enzalutamide. The clinical efficacy outcomes were overall survival (OS) and prostate-specific antigen (PSA) doubling time. The median PSA level was also assessed. In total, 223 mCRPC patients who underwent second-line hormonal therapy met all of the inclusion and exclusion criteria for this study. Among them, 65 (29.1%) patients were in the PSA response group and 158 (70.9%) were in the non-response group. The median age was 72.9 years. The median OS was 12.3 months (range: 9.9–19.9 months) and 9.6 months (range: 5.3–15.9 months) in the response and non-response groups, respectively, and the respective PSA doubling times were 9.0 months (range: 4.4–11.6 months) and 3.9 months (range: 2.2–9.1 months), with a median follow-up period of 10.5 months. A significantly longer median OS was seen in the PSA response group. This real-world database study demonstrated that clinical outcomes of second-line hormonal therapy were better in patients with a PSA response. Further studies are warranted to achieve a better understanding of second-line hormonal therapy for mCRPC in Asian populations.

Enzalutamide: A Review in Castration-Resistant Prostate Cancer

Oral enzalutamide (Xtandi^®), a second generation androgen receptor inhibitor, is indicated for the treatment of castration-resistant prostate cancer (CRPC) in numerous countries worldwide, with specific indications in this patient population varying between individual countries. Based on extensive experience in the clinical trial and/or real-world settings, oral enzalutamide 160 mg once daily is an effective and generally well tolerated treatment in a broad spectrum of patients with CRPC, including in nonmetastatic and metastatic disease and in chemotherapy-naive and -experienced metastatic CRPC. Enzalutamide is an emerging option for the treatment of men with nonmetastatic CRPC who are at high-risk for developing metastatic disease, and remains an important first-line option in chemotherapy-naive or -experienced patients with metastatic CRPC.

The androgen receptor antagonist enzalutamide induces apoptosis, dysregulates the heat shock protein system, and diminishes the androgen receptor and estrogen receptor β1 expression in prostate cancer cells

Enzalutamide's accepted mode of action is by targeting the androgen receptor's (AR) activity. In clinical practice, enzalutamide demonstrates a good benefit-risk profile for the treatment of advanced prostate cancer (PC), even after poor response to standard antihormonal treatment. However, since both, well-established antiandrogens and enzalutamide, target AR functionality, we hypothesized that additional unknown mechanisms might be responsible for enzalutamide's superior anticancer activity. In the current study, PC cells were incubated with enzalutamide and enzalutamide-dependent modulation of apoptotic mechanisms were assessed via Western blot analysis, TDT-mediated dUTP-biotin nick end-labeling assay, and nuclear morphology assay. Alterations of heat shock protein (HSP), AR, and estrogen receptor (ER) expression were examined by Western blot analysis. Enzalutamide attenuated the proliferation of PC cells in a time- and dose-dependent manner. In the presence of enzalutamide, apoptosis occurred which was shown by increased BAX expression, decreased Bcl-2 expression, nuclear pyknosis, and genomic DNA fragmentation. Moreover, enzalutamide inhibited the expression of HSPs primarily involved in steroid receptor stabilization and suppressed AR and ERβ1 expression. This study demonstrates for the first time that enzalutamide treatment of PC cells triggers varying molecular mechanisms resulting in antiproliferative effects of the drug. In addition to the well-characterized antagonistic inhibition of AR functionality, we have shown that enzalutamide also affects the intracellular synthesis of steroid receptor-associated HSPs, thereby diminishing the expression of AR and ERβ1 proteins and inducing apoptotic pathways. According to an indirect attenuation of HSP-associated factors such as steroid receptors, endometrial carcinoma, uterine leiomyosarcoma, and mamma carcinoma cells also demonstrated inhibited cell growth in the presence of enzalutamide. Our data, therefore, suggest that enzalutamide's high efficacy is at least partially independent of AR and p53 protein expression, which are frequently lost in advanced PC.

Serum testosterone level is a useful biomarker for determining the optimal treatment for castration-resistant prostate cancer

OBJECTIVE

Our aim was to evaluate the usefulness of serum testosterone to guide treatment decision for castration-resistant prostate cancer (CRPC).

METHODS

We conducted a retrospective analysis of 115 patients with CRPC treated with either abiraterone (n = 43) or enzalutamide (n = 72). A serum testosterone level was measured at time of starting of abiraterone or enzalutamide. We determined whether serum testosterone influenced the outcomes of androgen receptor (AR)-targeted therapy.

RESULTS

In the very-low testosterone group (<5 ng/dl), the rate of prostate-specific antigen (PSA) response was significantly higher among patients treated with abiraterone compared to enzalutamide (62 vs. 32%, respectively; P = 0.033), with no difference in the low testosterone group (5-<50 ng/dl) (93 vs. 81%, respectively; P = 0.429). During the median follow-up of 26 months, PSA progression-free survival was significantly longer in the low testosterone group than in the very-low testosterone group (12.2 vs. 4.5 months, P<0.001). In the very-low testosterone group, enzalutamide use (HR 3.07, 95% CI 1.36-6.94; P = 0.007), primary androgen deprivation therapy <12 months (HR 2.50, 95% CI 1.23-5.08; P = 0.011) and bone metastases (HR 2.60, 95% CI 1.20-5.64; P = 0.015) were significantly associated with PSA progression.

CONCLUSION

Patients with a serum testosterone level ≥5 ng/dl were more likely to receive therapeutic benefits from AR-targeted therapy compared to those with serum testosterone levels <5 ng/dl. However, even for those with a very low serum testosterone level, the efficacy of abiraterone was slightly higher than that of enzalutamide. Therefore, serum testosterone level is a useful biomarker for informing treatment selection for CRPC.

Safety and outcomes of new generation hormone-therapy in elderly chemotherapy-naive metastatic castration-resistant prostate cancer patients in the real world

BACKGROUND

Abiraterone acetate and enzalutamide are standard treatments for chemotherapy-naive metastatic castration-resistant prostate cancer (CN-mCRPC). The purpose of this study was to evaluate the effectiveness and safety of these medications in elderly (≥ 75 years old) compared with young CN-mCRPC patients in a real-world clinical setting. Secondarily, we explored the survival prognostic value of different anatomo-clinical factors in elderly group.

METHODS

In this retrospective observational multicentre study, we included 134 consecutive CN-mCRPC patients, 64 young and 70 elderly men, who had received AA or Enz.

RESULTS

We did not find significant differences in treatment duration [16.6 months, (95% CI 9-24.2 months) vs. 16.8 months (95% CI: 6.3-27.2 months); p = 0.926] and overall survival [median not reached vs. 23.3 months (95% CI 10.2-36.3 months); p = 0.131] between the young and elderly groups. In elderly group, the only predictors of overall survival with AA or Enz were good ECOG performance status and high G8 score. Adverse events of grade ≥3 was similar in elderly group (12.9%) and in the young group (15.6%). Treatment was discontinued due to AEs in 6.3% of young group and 18.6% of elderly group.

CONCLUSIONS

Effectiveness and safety of treatment of CN-mRCPC with Abiraterone acetate and enzalutamide were similar in older and younger patients, although treatment discontinuation due to AEs was more frequent in the older age group. In addition to ECOG PS, assessment using specific geriatric scales as G8 screening tool could help to identify patients aged ≥75 who would most benefit from treatment with new-generation hormone therapy.

The efficacy and toxicity of cabazitaxel for treatment of docetaxel-resistant prostate cancer correlating with the initial doses in Japanese patients

Background

We analyzed the efficacy and toxicity of cabazitaxel (CBZ) at high and low initial doses in Japanese patients with docetaxel-resistant castration-resistant prostate cancer (CRPC).

Methods

We retrospectively evaluated 118 patients who received CBZ for docetaxel-resistant CRPC in 10 university hospitals in Japan between 2014 and 2016. The rate of decrease of prostate-specific antigen (PSA), adverse events, progression-free survival (PFS), and overall survival (OS) were compared between patients receiving initially high (≥22.5 mg/m², n = 36) and low (≤20 mg/m², n = 80) CBZ doses. Factors associated with survival and grade 4 neutropenia were evaluated.

Results

PSA values decreased by > 50% in 22 patients (19%), with a higher frequency in the high-dose group than in the low-dose group (29 and 14%, P = 0.073). The median PFS time for the all-patient, high- and low-dose groups was 2.8 months (95% confidence interval [CI] 1.9–4.4), 2.1 months (1.2–5.5), and 3.0 months (2.0–4.4), respectively (P = 0.904). The median OS times were 16.3 months (95% CI 9.7–30.9), 30.9 months (11.8–47.4), and 10.2 months (8.6–20), respectively (P = 0.020). In multivariate analyses, PFS was significantly associated with existing bone metastasis at diagnosis (P = 0.005) and OS with PSA > 100 ng/ml (P = 0.007), hemoglobin < 12 g/dl (P = 0.030), and low initial CBZ dose (P = 0.030). Grade 4 neutropenia occurred in 53 patients (45%) and was associated with a low CBZ dose (hazard ratio 0.21, 95% CI 0.08–0.59, P = 0.002).

Conclusions

CBZ at a higher initial dose may have similar response rate and response duration, but longer survival duration after treatment with higher toxicity than a lower initial dose for docetaxel-resistant CRPC in Japanese patients.

The Effect of Targeted Therapy for Genitourinary Malignancies on Sexual Function and Fertility

PURPOSE OF REVIEW

Targeted therapy for genitourinary cancer is being used at an increasing rate. These medications show great survival benefit but are relatively lacking in long-term adverse effect data. With increasing survivability, measures to improve quality of life must be considered for GU cancer and a large proponent of this is sexual function.

RECENT FINDINGS

mTOR inhibitors have shown an effect on testosterone levels and may have a link to abnormal semen parameters. Tyrosine kinase inhibitors (TKIs) have shown no adverse sexual outcomes in the literature. There are laboratory links to tyrosine kinases having a beneficial effect on erectile and sexual function. Possible sexual side effects must be discussed with patients receiving a diagnosis of cancer. Further research is required to determine the exact mechanisms and outcomes of sexual function with new and emerging targeted therapy.

Prognostic and predictive biomarkers in prostate cancer: latest evidence and clinical implications

Advances in our understanding of the mechanisms driving castration-resistant prostate cancer have promoted the development of several new drugs including androgen receptor-directed therapy and chemotherapy. Concomitant docetaxel treatment at the beginning of hormonal therapy for metastatic prostate cancer has resulted in longer overall survival than with hormonal therapy alone. Elucidating an appropriate treatment sequence using these therapies is important for maximizing clinical benefit in castration-sensitive and castration-resistant prostate cancer patients. The development of advanced high-throughput ‘omics’ technology has enabled the use of novel markers to guide prognosis and treatment of this disease. In this review, we outline the genomic landscape of prostate cancer and the molecular mechanisms of castration-resistant progression, and how these affect the development of new drugs, and their clinical implications for selecting treatment sequence. We also discuss many of the potential tissue-based or liquid biomarkers that may soon enter clinical use, with the hope that several of these prognostic or predictive markers will guide precision medicine for prostate cancer patients in the near future.

[CLINICAL STUDY OF SEQUENTIAL THERAPY WITH ABIRATERONE AND ENZALUTAMIDE FOLLOWING DOCETAXEL THERAPY FOR CASTRATION-RESISTANT PROSTATE CANCER]

(Purpose) This study is to evaluate the efficacy and safety of sequential therapy with two novel drugs, abiraterone and enzalutamide after docetaxel (DOC) therapy for castration-resistant prostate cancer (CRPC). (Material and methods) Twenty-one patients were identified received sequential therapy with abiraterone and enzalutamide after DOC therapy at our institution. We investigated PSA response (decrease of 50% or more) to prior administered drug as primary endpoint, and overall survival rate and occurrence of adverse events as secondary endpoint. (Results) There were 12 patients in the group preliminarily administered enzalutamide (Group E) and 9 patients in the group preliminarily administered abiraterone (Group A). The novel drugs were administered immediately following DOC therapy in nearly all cases. Of the 9 patients in Group A, only one patient (11%) and of the 12 patients in Group E, only one patient (9%) achieved PSA decrease of 50% or more, thus resulting in a poor response rate. There was not significantly difference in both groups. The overall survival rates of Group A and E were not significantly difference. There were three adverse events which required change drug. Those were two cases (appetite loss and general fatigue) on enzalutamide and one case (edema) on abiraterone. (Conclusion) This study suggested that sequential therapy with abiraterone and enzalutamide after DOC therapy had poor clinical benefit regardless of the order of administration of both drugs.