Adjusting Overall Survival Estimates for Treatment Switching in Metastatic, Castration-Sensitive Prostate Cancer: Results from the LATITUDE Study

Overall survival of patients with CLL treated with ibrutinib in the first line compared to second-line ibrutinib after chemotherapy/chemoimmunotherapy

OBJECTIVE

To evaluate the overall survival (OS) of patients with chronic lymphocytic leukemia (CLL) receiving either ibrutinib monotherapy as a first-line (1L) treatment or chemotherapy/chemoimmunotherapy-based (CT/CIT) regimens in 1L followed by ibrutinib in the second line (1L CT/CIT-2L ibrutinib) after disease progression by emulating a randomized trial comparing both treatment sequences.

METHODS

Patient-level data from the RESONATE-2 trial (NCT01722487) and real-world PHEDRA databases were analyzed. Three scenarios were considered using the following data sources: (1) RESONATE-2, (2) combined RESONATE-2/PHEDRA, (3) combined RESONATE-2/PHEDRA for 1L ibrutinib and PHEDRA for 1L CT/CIT-2L ibrutinib. Propensity score-based weights and inverse probability of censoring weighting were used to adjust for baseline (Scenarios 2 and 3) and time-dependent confounding (all scenarios), and to address potential biases. A weighted Cox proportional hazards model was used to estimate the OS hazard ratio (HR) and 95% confidence interval (CI) for 1L ibrutinib versus 1L CT/CIT-2L ibrutinib.

RESULTS

Results from Scenario 1 showed a significantly lower risk of death with 1L ibrutinib compared with 1L chlorambucil followed by 2L ibrutinib (HR 0.35 [95% CI 0.20-0.62]). Results from Scenarios 2 and 3 demonstrated a reduced risk of death with 1L ibrutinib compared with 1L CT/CIT-2L ibrutinib (HR 0.35 [0.21-0.61] and 0.64 [0.39-1.04], respectively).

CONCLUSION

The analyses consistently showed a reduced risk of death when ibrutinib was used as a 1L treatment in CLL compared with delaying its use until 2L after CT/CIT regimens, which suggests that initiating ibrutinib in 1L is advantageous for improving survival outcomes.

Emergence of triplet therapy for metastatic castration-sensitive prostate cancer: An updated systematic review and network meta-analysis

INTRODUCTION

There have been a growing number of treatment options available for men with metastatic castration-sensitive prostate cancer. Not only have newer agents entered the clinical landscape, there is a trend toward treatment intensification by combining multiple agents simultaneously. We aim to assess the best contemporary treatment option for men with mCSPC.

MATERIALS AND METHODS

We perform an updated systematic review and network meta-analysis of randomized control trials that evaluated systemic therapies in men with castration-sensitive prostate cancer. We searched multiple databases up to April 2022. We included all randomized trials assessing the effect of systemic agents. We performed subgroup analyses based on disease volume and timing of presentation. Statistical analysis was performed with Bayesian methods.

RESULTS

We found 10 eligible trials with 10,065 patients who were included in this analysis. Triplet therapy with darolutamide or abiraterone with docetaxel and ADT improved overall survival. In the sensitivity analysis, the respective hazard ratios for triplet therapy was HR 0.70 (95%CI 0.61-0.80) compared to docetaxel+ADT and 0.77 (95%CI 0.65-0.91) compared to androgen receptor pathway inhibitors+ADT combinations. It was estimated that there was 96% chance that one of the triplet therapy combinations were the best treatment option from an OS perspective. Triplet therapy also improved progression-free survival. These benefits were pronounced in men with high-volume disease burden and those with de novo metastatic disease.

CONCLUSION

The finding suggest that triplet therapy is likely the most efficacious available option in men with metastatic, castration-sensitive prostate cancer, especially in those with high-volume disease burden.

Review of second-generation androgen receptor inhibitor therapies and their role in prostate cancer management

PURPOSE OF REVIEW

We review the published literature on the indications of second-generation androgen receptor inhibitors, Poly(ADP-Ribose) Polymerase (PARP) inhibitors, combination therapies, and their evolution throughout the advanced prostate cancer continuum.

RECENT FINDINGS

Enzalutamide trials have published data supporting its use in metastatic hormone-sensitive prostate cancer (mHSPC), nonmetastatic castration-resistant prostate cancer (nmCRPC), and metastatic castration-resistant prostate cancer (mCRPC). Apalutamide trials have supported its indication for mHSPC and nmCRPC. Darolutamide trials currently support its use for nmCRPC. Abiraterone trials have supported its use in mCRPC and mHSPC. Olaparib and rucaparib have shown clinical benefit in heavily pretreated patients with mCRPC and DNA repair mutation genes.

SUMMARY

Phase 3 trials and peer-reviewed literature demonstrate that enzalutamide, apalutamide, and darolutamide prolong overall survival (OS) in men with nmCRPC. Abiraterone, enzalutamide, and apalutamide improve OS in men with mHSPC. Abiraterone and enzalutamide have data supporting improvement in OS in men with mCRPC.

Estimation of Overall Survival with Subsequent Treatment Effect by Applying Inverse Probability of Censoring Weighting in the LATITUDE Study

Background

In the LATITUDE study (ClinicalTrials.gov, NCT01715285), compared with placebos, abiraterone acetate plus prednisone (AAP) with androgen deprivation therapy (ADT) provided significant overall survival (OS) benefit in high-risk metastatic castration-sensitive prostate cancer (mCSPC) patients. It is controversial whether survival benefits would remain if all patients in the placebo group subsequently received life-extending therapies.

Objective

To estimate treatment effect in the case of all patients in the placebo group receiving life-extending subsequent therapies.

Design, setting, and participants

A post hoc analysis of LATITUDE final-analysis data was carried out (setting and participants have been reported previously).

Intervention

AAP or placebos plus ADT.

Outcome measurements and statistical analysis

We applied the inverse probability of censoring weighting (IPCW) method to represent the situation in which all patients in the placebo group would have received life-extending subsequent therapies. The OS hazard ratio (HR) of AAP versus placebos and associated 95% confidence interval (CI) were estimated using a Cox proportional hazards model.

Results and limitations

Of the 581 eligible patients in the placebo group, 237 (40.8%) did not receive life-extending subsequent therapies. From the unadjusted intention-to-treat analysis, the HR for OS for AAP versus placebos was 0.661 (95% CI 0.564–0.775). Using IPCW to adjust for patients in the placebo group without life-extending subsequent therapies, the HR was 0.732 (95% CI 0.604–0.887). A limitation is a lack of proof that the Cox proportional hazards model for the absence of life-extending subsequent therapy is correctly specified for the IPCW method.

Conclusions

Treatment with AAP exerts OS benefit over placebos in high-risk mCSPC patients, regardless of whether life-extending subsequent therapy is given.

Patient summary

In a previous study, high-risk metastatic castration-sensitive prostate cancer patients who received abiraterone acetate plus prednisone (AAP) with androgen deprivation therapy generally survived longer than those given placebos. The benefit of adding AAP continues regardless of whether life-extending subsequent therapy is given.

Treatment results of radiotherapy to both the prostate and metastatic sites in patients with bone metastatic prostate cancer

Although systemic therapy is the standard treatment for metastatic prostate cancer, a randomized controlled trial showed radiotherapy to the prostate improved overall survival of metastatic prostate cancer patients with the low metastatic burden. Additionally, a randomized phase II trial showed that metastasis-directed therapy for oligo-recurrent prostate cancer improved androgen-deprivation therapy (ADT)-free survival. Therefore, administering radiotherapy to both prostate and metastatic regions might result in better outcomes. Thus, we report the treatment results of radiotherapy to both prostate and metastatic regions. Our institutional database was searched for patients who received radiotherapy to the prostate and metastatic regions. We summarized patient characteristics and treatment efficacy and performed statistical analysis to find possible prognostic factors. A total of 35 patients were included in this study. The median age was 66 years, and the median initial prostate-specific antigen (PSA) level was 32 ng/ml. The Gleason score was 7 in 10 patients, 8 in 13 patients, and 9 in 12 patients. The median radiotherapy dose was 72 Gy to the prostate and 50 Gy to the metastatic bone region. The 8-year overall survival, cause-specific survival, progression-free survival, and freedom from biochemical failure rate were 81, 85, 53, and 57%. Among the 35 patients, 12 were disease-free even after ADT was discontinued. In selected patients with metastatic prostate cancer, ADT and radiotherapy to the prostate and metastatic sites were effective. Patients with good response to ADT may benefit from radiotherapy to both prostate and metastatic regions.

Abiraterone acetate in combination with androgen deprivation therapy compared to androgen deprivation therapy only for metastatic hormone-sensitive prostate cancer

BACKGROUND

Systemic androgen deprivation therapy (ADT), also referred to as hormone therapy,àhas long been the primary treatment for metastatic prostate cancer. Additional agents have been reserved for the castrate-resistant disease stage when ADT start becoming less effective. Abiraterone is an agent with an established role in that disease stage, which has only recently been evaluated in the hormone-sensitive setting.

OBJECTIVES

To assess the effects of early abiraterone acetate, in combination with systemic ADT, for newly diagnosed metastatic hormone-sensitive prostate cancer.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, six other databases, two trials registries, grey literature, and conference proceedings, up to 15 May 2020. We applied no restrictions on publication language or status.

SELECTION CRITERIA

We included randomized trials, in which men diagnosed with hormone-sensitive prostate cancer were administered abiraterone acetate and prednisolone with ADT or ADTàalone.

DATA COLLECTION AND ANALYSIS

Two review authors independently classified studies and abstracted data from the included studies. We performed statistical analyses using a random-effects model. We rated the quality of evidence according to the GRADE approach.

MAIN RESULTS

The search identified two randomized controlled trials (RCT), with 2201 men, who were assigned to receive either abiraterone acetate 1000 mg once daily and low dose prednisone (5mg) in addition to ADT, or ADT alone. In the LATITUDE trial, the median age and range of men in the intervention group was 68 (38 to 89) years, and 67 (33 to 92) years in the control group. Nearly all of the men in thisàstudy (97.6%) had prostate cancer with a Gleason score of at least 8 (ISUP grade group 4). Primary outcomes The addition of abiraterone acetate to ADT reduces the probability of death from any cause compared to ADT alone (hazard ratio [HR] 0.64, 95% confidence interval [CI] 0.56 to 0.73; 2 RCTs, 2201 men; high certainty of evidence); this corresponds to 163 fewer deaths per 1000 men with hormone-sensitive metastaticàprostate cancerà(210 fewer to 115 fewer) at five years. Abiraterone acetate in addition to ADT probably results in little to no differenceàin quality of life compared to ADT alone, measured with the Functional Assessment of Cancer Therapy-prostate total score (FACT-P; range 0 to 156; higher values indicates better quality of life),àat 12 months (mean difference [MD] 2.90 points, 95% CI 0.11 to 5.60; 1 RCT, 838 men; moderate certainty of evidence). Secondary outcomes Abiraterone plus ADT increases the risk of grades III to V adverse events compared to ADT alone (risk ratio [RR] 1.34, 95% CI 1.22 to 1.47; 1 RCT, 1199 men; high certainty of evidence); this corresponds to 162 more grade III to Vàevents per 1000 men with hormone-sensitive metastaticàprostate cancerà(105 more to 224 more) at a median follow-up of 30àmonths. Abiraterone acetate in addition to ADT probably reduces the probability of death due to prostate cancer compared to ADT alone (HR 0.58, 95% CI 0.50 to 0.68; 2 RCTs, 2201 men; moderate certainty of evidence). This corresponds to 120 fewer death from prostate cancer per 1000 men with hormone-sensitive metastaticàprostate cancerà(95% CI 145 fewer to 90 fewer) afteràa median follow-up of 30 months. The addition of abiraterone acetate to ADT probably decreases the probability of disease progression compared to ADT alone (HR 0.35, 95%CI 0.26 to 0.49; 2 RCTs, 2097 men; moderate certainty of evidence). This corresponds to 369 fewer incidences of disease progression per 1000 men with hormone-sensitive metastaticàprostate cancerà(456 fewer to 256 fewer)àafter a median follow-up of 30 months. The addition of abiraterone acetate to ADT probably increases the risk of discontinuing treatment due to adverse events compared to ADT alone (RR 1.50, 95% CI 1.17 to 1.92; 1 RCT, 1199 men; moderate certainty of evidence). This corresponds to 51 more men (95% CI 17 more to 93 more) discontinuing treatment because of adverse events per 1000 men treated with abiraterone acetate and ADT compared to ADT alone afteràa median follow-up of 30 months.

AUTHORS' CONCLUSIONS

The addition of abiraterone acetate to androgen deprivation therapy improves overall survival but probably not quality of life. Itàprobably also extends disease-specific survival, and delays disease progression compared to androgen deprivation therapy alone. However, the risk of grades III to V adverse events is increased, and probably, so is the risk of discontinuing treatment due to adverse events.