Prostate-specific antigen response to deferred combined androgen blockade therapy using bicalutamide predicts survival after subsequent oestrogen and docetaxel therapies in patients with castration-resistant prostate cancer

Real-world outcomes of abiraterone and enzalutamide in first-line treatment of metastatic castration-resistant prostate cancer: which patients benefit most?

OBJECTIVES

Abiraterone and enzalutamide are two oral novel androgen receptor axis-targeted agents approved for the treatment of castration-resistant prostate cancer (mCRPC). Despite the availability of multiple treatments, there is a need to improve the knowledge and management of these drugs in the real-world setting, especially in patient groups under-represented in clinical trials. Our aim was to review the outcome of patients with chemotherapy-naïve mCRPC treated with abiraterone or enzalutamide in routine clinical practice in order to identify factors that are predictive for response.

METHODS

This observational retrospective study was performed in a Spanish tertiary hospital and included men with chemotherapy-naïve mCPRC who started treatment with abiraterone or enzalutamide between September 2012 and November 2018. The study end date was 30 October 2020.

RESULTS

Ninety patients with mCRPC were included, 57 with abiraterone and 33 with enzalutamide. Median overall survival (OS) was 26.87 months (95% CI 19.68 to 34.05), with no difference found between the two treatment groups. Nine variables were related to increased OS in the univariate analysis: Eastern Cooperative Oncology Group (ECOG) performance status (0-1 vs 2), pain (need of opioids for cancer pain), visceral disease, ≥3 bone lesions, exclusively lymph node metastases, baseline prostate specific antigen (PSA) (<50 vs ≥50 ng/dL and <20 vs ≥20 ng/dL), haemoglobin (<12 vs ≥12 g/dL) and alkaline phosphatase (≤116 vs >116 IU/L). A PSA response >50% was observed in 65 patients (76.5%). In the multivariate analysis, ECOG performance status, pain, visceral disease and alkaline phosphatase provided independent prognostic information. Median OS by Kaplan-Meier analysis was significantly longer for patients with a PSA response (32.1 vs 17.9 months; HR 0.46, 95% CI 0.27 to 0.78; p=0.003).

CONCLUSIONS

This study assessed the efficacy of abiraterone and enzalutamide in a real-world setting, including patients under-represented in pivotal studies. Some clinical factors were correlated with improved OS in chemotherapy-naïve men with mCPRC treated with these drugs.

Efficacy of abiraterone acetate for high-risk hormone-naïve metastatic prostate cancer: A comparison with combined androgen blockade therapy with bicalutamide and androgen deprivation therapy alone

BACKGROUND

The treatment landscape for men with metastatic hormone-naïve prostate cancer (mHNPC) has dramatically changed with the approval of next-generation anti-androgen drugs. We compared the treatment efficacy of abiraterone with that of combined androgen blockade (CAB) therapy and androgen deprivation therapy (ADT) alone in men with high-risk mHNPC.

METHODS

In total, 146 Japanese men with high-risk mHNPC were retrospectively analyzed. As initial hormonal therapy, 30, 83, and 33 men were treated with ADT plus abiraterone (ABI group), ADT plus bicalutamide (CAB group), and ADT alone (ADT group), respectively. Treatment efficacy was compared using time to castration resistance (TTCR) and prostate-specific antigen (PSA) response among the groups. Propensity score matching analysis was also performed to adjust for baseline differences.

RESULTS

The median (95% confidence interval [CI]) TTCR in the ABI, CAB, and ADT groups were not reached, 10.7 (7.6-13.8) months and 11.0 (7.9-12.4) months, respectively, and it was significantly longer in the ABI group than in the other groups (p = 0.0012, p = 0.0008). In propensity score matching analysis, the median TTCR was also significantly longer in the ABI group than in the other groups (hazard ratio [HR], 0.47; 95% CI, 0.22-0.98; p = 0.010; HR, 0.32; 95% CI, 0.12-0.85; p = 0.004). The number of men who achieved PSA levels ≤0.2 ng/mL after propensity score matching were significantly higher in the ABI group than in the other groups.

CONCLUSIONS

Our results provide important evidence regarding the superiority of abiraterone over CAB therapy and ADT alone for initial treatment for men with newly diagnosed mHNPC.

PSA Kinetics as Prognostic Markers of Overall Survival in Patients with Metastatic Castration-Resistant Prostate Cancer Treated with Abiraterone Acetate

Background

Abiraterone acetate (AA) is widely used in the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC). However, a significant percentage of patients will still progress, highlighting the need to identify patients more likely to benefit from AA. Parameters linked to prostate-specific antigen (PSA) kinetics are promising prognostic markers. We have examined clinical and PSA-related factors potentially associated with overall survival (OS) in patients treated with AA.

Methods

Between 2011 and 2014, 104 patients with mCRPC treated with AA after progression to docetaxel at centers of the Catalan Institute of Oncology were included in this retrospective study. Patients were assessed monthly. Baseline characteristics and variables related to PSA kinetics were included in univariate and multivariate analyses of OS.

Results

Median OS was 16.4 months (range 12.4-20.6) for all patients. The univariate analysis identified the following baseline characteristics as significantly associated with OS: ECOG PS, location of metastases, time between starting androgen deprivation therapy and starting AA, time between stopping docetaxel treatment and starting AA, neutrophil-lymphocyte ratio (NLR), alkaline phosphatase levels, and PSA levels. Factors related to PSA kinetics associated with longer OS were PSA response >50%, early PSA response (>30% decline at four weeks), PSA decline >50% at week 12, PSA nadir <2.4ng/mL, time to PSA nadir >140 days, the combination of PSA nadir and time to PSA nadir, and low end-of-treatment PSA levels. The multivariate analysis identified ECOG PS (HR 37.46; p<0.001), NLR (HR 3.7; p<0.001), early PSA response (HR 1.22; p=0.002), and time to PSA nadir (HR 0.39; p=0.002) as independent prognostic markers.

Conclusion

Our results indicate an association between PSA kinetics, especially early PSA response, and outcome to AA after progression to docetaxel. Taken together with other factors, lack of an early PSA response could identify patients who are unlikely to benefit from AA and who could be closely monitored with a view to offering alternative therapies.

Prognostic role of early PSA drop in castration resistant prostate cancer patients treated with abiraterone acetate or enzalutamide

BACKGROUND

Previous studies demonstrated a predictive value of prostate-specific antigen (PSA) kinetics for treatment outcome. Our retrospective study evaluates the prognostic role of early PSA drop in metastatic castration resistant prostate cancer (mCRPC) patients receiving abiraterone acetate (AA) or enzalutamide (E).

METHODS

All mCRPC patients treated with AA or E at the San Luigi Hospital in Orbassano between 2010 and 2018 and at the Ordine Mauriziano Hospital in Turin between 2014 and 2018 were included in this retrospective study. Only patients with an early PSA (measured 28-60 days after the beginning of the treatment) were included in the analysis. Patients were divided in early responders and non-early responders according to early PSA response (drop≥50% from baseline). Univariate and multivariate analyses for progression free survival (PFS) and overall survival (OS) were performed.

RESULTS

Of 144 patients with early PSA value, 61 (42.4%) patients received E (docetaxel-naïve 42, post-docetaxel 19) and 83 (57.6%) received AA (docetaxel-naïve 44, post-docetaxel 39). Seventy-five (52.1%) patients achieved early PSA drop. In docetaxel-naïve setting (N.=86), median PFS was 14.9 (with early PSA drop) vs. 8.8 months (without early PSA drop, P=0.001). In post-docetaxel setting (N.=58) median PFS was 11.9 vs. 4.5 months (P<0.001). Globally, median PFS was 14.9 vs. 6.3 months in patients with and without early PSA drop, respectively (P<0.001). In docetaxel-naïve setting, patients with early PSA drop had a median OS of 39.5 vs. 18.8 months (P=0.12). In post-docetaxel setting median OS was 29.6 vs. 10.7 months (P=0.01). Comprehensively, median OS was 31.9 vs. 16.3 (P=0.002) in patients with and without early PSA drop, respectively. At multivariate analysis, early PSA drop confirmed an independent association with PFS (HR 0.21; 95% CI: 0.12-0.38, P<0.001) and OS (HR 0.25; 95% CI: 0.12-0.50, P<0.001).

CONCLUSIONS

mCRPC patients treated with AA or E, in docetaxel-naïve or post-docetaxel setting, with early PSA drop had significantly better OS and PFS.

Correlation of Prostate-specific Antigen Kinetics with Overall Survival and Radiological Progression-free Survival in Metastatic Castration-sensitive Prostate Cancer Treated with Abiraterone Acetate plus Prednisone or Placebos Added to Androgen Deprivation Therapy: Post Hoc Analysis of Phase 3 LATITUDE Study

BACKGROUND

LATITUDE, a randomized, double-blind trial, compared abiraterone acetate and prednisone (AAP) + androgen deprivation therapy (ADT) versus placebo (PBO) + ADT in high-risk metastatic castration-sensitive prostate cancer (mCSPC).

OBJECTIVE

To assess the correlation of prostate-specific antigen (PSA) kinetics with overall survival (OS) and radiological progression-free survival (rPFS).

DESIGN, SETTING, AND PARTICIPANTS

A post hoc analysis of data from 597 men receiving AAP + ADT and 602 receiving PBO + ADT.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The associations of PSA-related outcomes (rates of confirmed 50% [PSA50] and 90% [PSA90] decline from baseline PSA [Prostate Cancer Working Group 2 criteria], rates of PSA < 0.2 ng/ml, median nadir PSA, time to PSA nadir [TPN], and time to PSA progression [TPP] with long-term outcomes [OS and rPFS]) were evaluated. Hazard ratios (HRs) were estimated using Cox proportional hazard model. Correlations of TPP with coprimary endpoints rPFS and OS were evaluated using Kendall's tau (KT).

RESULTS AND LIMITATIONS

AAP + ADT significantly delayed median TPP versus PBO + ADT (33.2 vs 7.4 mo; HR: 0.3, p <  0.001). TPP correlated with rPFS (KT = 0.921) and OS (KT = 0.666). In the AAP + ADT group, 91% had PSA50 and 79% had PSA90 responses (relative risk [RR]: 1.36 and 2.30, respectively; p <  0.001 for both comparisons vs PBO + ADT). Compared with nonresponders, PSA50 and PSA90 responders had reduced risk of death (RR: 0.44 and 0.12, respectively). At 6 mo, 40% receiving AAP + ADT and 6.5% receiving PBO + ADT achieved PSA ≤0.1 ng/ml, which was significantly associated with longer rPFS and OS. Median nadir PSA was 0.09 ng/ml with AAP + ADT versus 2.36 ng/ml with PBO + ADT. Median TPN (AAP + ADT, 6.4 mo; PBO + ADT, 3.8 mo) positively correlated with rPFS and OS.

CONCLUSIONS

Superior PSA response dynamics with AAP + ADT versus ADT + PBO strongly correlated with long-term outcomes of rPFS and OS in high-risk mCSPC.

PATIENT SUMMARY

We found that low prostate-specific antigen levels (≤0.1 ng/ml) after 6 mo may indicate a good long-term response to treatment. Our results need confirmation.

Effectiveness of Deferred Combined Androgen Blockade Therapy Predicts Efficacy in Abiraterone Acetate Treated Metastatic Castration-Resistant Prostate Cancer Patients after Docetaxel

Introduction: Conventional anti-androgen regimens were widely used as an initiation or combined androgen blockade (CAB) therapy in advanced prostate cancer patients. Currently, new androgen pathway inhibitors such as abiraterone acetate (AA) and enzalutamide had been proven effective in metastatic castration resistant prostate cancer. In this study, we attempt to analyze the role of conventional anti-androgen drugs as deferred CAB therapy in castration-resistant prostate cancer patients.

Materials and Methods: From 2012 to 2017, 48 metastatic castration-resistant prostate cancer (CRPC) patients who received sequential treatments with primary androgen blockade, oral anti-androgen regimens, and docetaxel followed by AA treatment were included. We defined effective deferred CAB as any decline of PSA after add-on antiandrogen after CRPC. Patients were separated into effective and ineffective deferred CAB. Comparison between two groups in the first line androgen deprivation therapy duration, CRPC PSA level, pre-AA PSA level, chemotherapy dosages, duration, and patients progression free survival and overall survival after AA treatment were analyzed.

Results: Twenty-three patients (47.9%) achieved PSA decline after deferred CAB. Among total 48 patients, 24 patients experienced PSA decline more than 50% after AA treatment. The median PSA progression-free survival and overall survival after AA treatment in the total cohort of 48 patients were 4.4 and 24.3 months, respectively. The effective deferred CAB group showed significantly lower PSA level, lower percentage of PSA progression, higher total follow-up duration, higher percentage of surviving patients, better progression free survival, and overall survival estimate after AA treatment. Of the eight variables analyzed, effectiveness in deferred CAB showed positive association to progression free survival (HR 0.29, 95% CI 0.12–0.67, p = 0.004) and overall survival (HR 0.24, 95% CI 0.07–0.81, p = 0.022). First line androgen deprivation therapy (ADT) duration also showed positive association to overall survival (HR 0.95, 95% CI 0.91–0.99, p = 0.023).

Conclusions: Effectiveness of deferred CAB therapy was positively associated with progression free survival and overall survival of AA treatment after docetaxel. It can be used as a pre-treatment predictor.

Very Early PSA Response to Abiraterone in mCRPC Patients: A Novel Prognostic Factor Predicting Overall Survival

Background: Abiraterone Acetate (AA) is approved for the treatment of mCRPC after failure of androgen deprivation therapy in whom chemotherapy is not yet clinically indicated and for treatment of mCRPC progressed during or after docetaxel-based chemotherapy regimen. The aim of this study is to evaluate the role of early PSA decline for detection of therapy success or failure in mCRPC patients treated with AA in post chemotherapy setting.

Patients and Methods: We retrospectively evaluated 87 patients with mCRPC treated with AA. Serum PSA levels were evaluated after 15, 90 days and then monthly. The PSA flare phenomenon was evaluated, according to a confirmation value at least 1 week apart. The primary endpoint was to demonstrate that an early PSA decline correlates with a longer progression free survival (PFS) and overall survival (OS). The secondary endpoind was to demonstrate a correlation between better outcome and demographic and clinical patient characteristics.

Results: We have collected data of 87 patients between Sep 2011 and Sep 2014. Early PSA response (≥50% from baseline at 15 days) was found in 56% evaluated patients and confirmed in 29 patients after 90 days. The median PFS was 5.5 months (4.6–6.5) and the median OS was 17.1 months (8.8–25.2). In early responders patients (PSA RR ≥ 50% at 15 days), we found a significant statistical advantage in terms of PFS at 1 year, HR 0.28, 95%CI 0.12–0.65, p = 0.003, and OS, HR 0.21 95% CI 0.06–0.72, p = 0.01. The results in PFS at 1 years and OS reached statistical significance also in the evaluation at 90 days.

Conclusion: A significant proportion (78.6%) of patients achieved a rapid response in terms of PSA decline. Early PSA RR (≥50% at 15 days after start of AA) can provide clinically meaningful information and can be considered a surrogate of longer PFS and OS.

Sequencing current therapies in the treatment of metastatic prostate cancer

The standard treatment for metastatic prostate cancer is androgen deprivation therapy. However, progressive, metastatic disease usually develops, giving rise to metastatic castration-resistant prostate cancer (mCRPC). Great improvements have been made recently in the management of mCRPC, with current approved treatments including chemotherapy, androgen receptor-targeted agents, immunotherapies and radiopharmaceuticals. While the emergence of multiple effective therapies is encouraging, devising a treatment strategy can be difficult and it is becoming increasingly important, and challenging, to identify factors that influence the ideal timing of specific therapies. Considering where to place these agents in the treatment schedule of mCRPC, or whether these agents should be sequenced or combined to derive the optimal benefit for the patient, is not yet clear. Furthermore, cross-resistance may exist between these agents, which may ultimately influence treatment decisions and sequence choices. Preliminary data are emerging regarding the safety and activity for sequential treatment regimens, but there are currently no prospective studies. As prostate cancer is highly heterogeneous clinically, it is likely that no single treatment sequence will be optimal for all patients. However, at present, there are no validated biomarkers to guide individualized treatment for mCRPC. Here we review available data for the different mCRPC treatments, discussing potential sequencing of agents and possible cross-resistance or synergy among the recently approved and emerging therapies.

Intermittent tri-weekly docetaxel plus bicalutamide in patients with castration-resistant prostate cancer: a single-arm prospective study using a historical control for comparison

Whether continuous docetaxel (DTX) chemotherapy offers an advantage over intermittent therapy for castration-resistant prostate cancer (CRPC) is unknown. In this study, we evaluated the efficacy, toxicity and quality of life (QoL) of intermittent tri-weekly DTX with bicalutamide in CRPC. Forty-two patients (group A) with CRPC were enrolled. The patients received intravenous DTX (75 mg m(-2)) once tri-weekly with oral bicalutamide (50 mg) once daily. Patients had a DTX holiday when the prostate-specific antigen (PSA) level declined ≥50%. DTX was restarted in patients with a PSA increase ≥25%. Sixty patients (group B) who had matching characteristics and had continuously received DTX without bicalutamide for 10-12 cycles were also enrolled. There were no statistically significant differences in progression-free survival (8 months vs. 9 months, P=0.866) or overall survival (19 months vs. 21 months, P=0.753) between groups A and B; however, the proportions of patients in group A with all grades of neutropenia (33% vs. 58%, P=0.013) and nausea/vomiting (11% vs. 29%, P=0.024) were significantly less compared to group B. A significant improvement in the global health and fatigue scores was recorded for group A post-chemotherapy compared to pre-chemotherapy (P<0.05). The fatigue, nausea/vomiting and appetite loss scores in group B were increased post-chemotherapy compared to pre-chemotherapy (P<0.05). In conclusion, intermittent tri-weekly DTX plus bicalutamide is well tolerated and has the potential to achieve comparable disease control with an improvement in QoL for patients with CRPC.