Olaparib Outcomes in Metastatic Castration-Resistant Prostate Cancer: First Real-World Experience in Safety and Efficacy from China

Homologous recombination repair gene alteration is strongly associated with more prostate-specific membrane antigen-positive metastases in newly diagnosed hormone-sensitive prostate cancer with ≤5 conventional imaging defined distant metastases

BACKGROUND

The differences in imaging between prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) and conventional imaging (CI) significantly impact disease staging, subsequently influencing the scope and clinical efficacy of stereotactic body radiotherapy (SBRT). In this multicenter retrospective study, we aimed to explore the effect of homologous recombination repair (HRR) gene status on the imaging differences between PSMA PET/CT and CI, which may have important implications for treatment selection.

PATIENTS AND METHODS

A total of 1214 newly diagnosed hormone-sensitive prostate cancer (HSPC) patients with ≤ 5 CI-defined distant metastatic lesions were included. All patients underwent PSMA PET/CT, CI, and circulating tumor DNA testing for 19 HRR genes. The PSA response was defined as achieving a PSA level of < 0.1 ng/ml after 6 months.

RESULTS

The median PSA level was 22.7 ng/ml. In the comparison of bone metastasis detection rates, the proportion of patients with higher detection rates on PSMA PET/CT than on CI was similar between BRCA mutation carriers and those with other HRR gene mutations (43.6% vs. 39.3%, p = 0.554), yet significantly higher in both groups compared to non-mutation carriers (20.5%, p = 0.00001). Similar results were observed in the analysis of metastasis detection rates for distant lymph nodes and regional lymph nodes. In non-metastatic HSPC patients without PSMA-positive distant disease who accepted radical prostatectomy (RP), patients without HRR gene mutations exhibited a significantly higher PSA response rate compared to HRR gene mutated patients (96.9% vs. 90.2%, p = 0.003).

CONCLUSIONS

HRR gene alterations were significantly associated with a higher number of PSMA-positive metastases in newly diagnosed HSPC with ≤ 5 CI-defined distant metastases and worse outcomes in non-metastatic HSPC accepting RP. This finding suggests that HRR gene status should be considered as a potential indicator for recommending PSMA PET/CT in the design of clinical trials involving SBRT and in shaping imaging strategies.

Real-world efficacy and safety of combined first-line treatment with PARP inhibitors and novel hormonal therapy in mCRPC patients with HRR gene mutations

Objective

This study evaluated the real-world efficacy and safety of combining PARP inhibitors with novel hormonal therapy (NHT) as a first-line treatment in Chinese patients with metastatic castration-resistant prostate cancer (mCRPC) harboring homologous recombination repair (HRR) gene mutations.

Methods

We enrolled 41 mCRPC patients who received at least 1 month of combined treatment with PARP inhibitors and NHT. Patients were divided into two groups: Cohort A (mutations in BRCA1, BRCA2, or ATM genes) and Cohort B (mutations in other HRR genes). The primary endpoint was imaging-based progression-free survival (PFS), with secondary endpoints including objective response rate (ORR), disease control rate (DCR), overall survival (OS), PSA50 response, and adverse events (AEs). To ensure accurate research results and control confounding factors, we will employ multivariate Cox proportional hazards models to evaluate key variables affecting mCRPC patient survival outcomes.

Results

This study enrolled 41 patients, 22 in Cohort A and 19 in Cohort B. The median PFS for all patients was 21.8 months, and the median OS had yet to be reached. The overall ORR was 48.8%, and the DCR was 61.0%. Specifically, the median PFS for Cohort A was 21.8 months compared to 14.5 months for Cohort B. The median OS had yet to be reached for either cohort. Regarding efficacy, 81.8% of patients in Cohort A and 73.7% in Cohort B achieved a PSA50 response. Imaging assessments showed ORRs of 54.6% for Cohort A and 42.1% for Cohort B, with DCRs of 72.7% and 47.4%, respectively. 85.4% of patients experienced grade 1 or 2 adverse events, and 51.2% encountered grade 3 or 4. In the multivariate Cox regression analysis focusing on PFS, the Gleason score was identified as a significant predictor (HR = 5.8, 95% CI: 1.65-20.2, p = 0.006).

Conclusion

Combined first-line treatment with PARP inhibitors and NHT is effective and well-tolerated in mCRPC patients with HRR gene mutations, particularly those with BRCA1, BRCA2, or ATM mutations. These findings underscore the potential of this therapeutic combination in managing mCRPC in the Chinese population, suggesting a favorable outcome for those with specific genetic backgrounds.

Protocol for CHAMPION study: a prospective study of maximal-cytoreductive therapies for patients with de novo metastatic hormone-sensitive prostate cancer who achieve oligopersistent metastases during systemic treatment with apalutamide plus androgen deprivation therapy

BACKGROUND

The proposed trial is to examine the feasibility of prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT)-guided cytoreduction plus apalutamide and androgen deprivation therapy (ADT) for newly diagnosed metastatic hormone-sensitive prostate cancer (mHSPC) at oligometastatic state.

METHODS

CHAMPION (NCT05717582) is an open-label, single-arm, phase II trial, planning to enroll newly diagnosed mHSPC cases with oligometastases (≤ 10 distant metastatic sites in conventional imaging). Patients will receive 6 cycles of apalutamide plus ADT. Patients with oligometastatic disease at PSMA PET/CT after 3 treatment cycles will receive cytoreductive radical prostatectomy. PSMA PET/CT-guided metastasis-directed external radiation therapy will be determined by the investigators. Apalutamide plus ADT will be continued for 2 weeks postoperatively. The primary endpoint is the proportion of patients with undetectable prostate-specific antigen (PSA), no disease progression, and no symptom deterioration after 6 cycles of apalutamide plus ADT. Secondary endpoints include the percentage of patients with PSA ≤ 0.2 ng/mL and oligometastases by the end of 3 treatment cycles, PSA response rate, and safety. Fleming's two-stage group sequential design will be adopted in the study, where the null hypothesis is that the rate of patients with an undetectable PSA is ≤ 40% after 6 cycles of treatment, while the alternate hypothesis is an undetectable PSA of > 60%; with one-sided α = 0.05, power = 0.80, and an assumed dropout rate of 10%, the required number of patients for an effective analysis is 47. Enrolment in the study commenced in May 2023.

DISCUSSION

The multi-modal therapy based on treatment response may improve the prognosis of newly diagnosed mHSPC patients with oligometastases.

TRIAL REGISTRATION

The study is registered with Clinical Trials.Gov (NCT05717582). Registered on 8th February 2023.

PARP Inhibitors in Metastatic Prostate Cancer: A Comprehensive Systematic Review and Meta-analysis of Existing Evidence

Poly (ADP-ribose) polymerase inhibitors (PARPi) represent an option in selected cases of metastatic castration-resistant prostate cancer (mCRPC). The aim of the present systematic review and meta-analysis is to evaluate the efficacy and safety of approved (Olaparib, Rucaparib) and investigational (Talazoparib, Niraparib, Veliparib) PARPi in mCRPC patients. Three databases were queried for studies analyzing oncological outcomes and adverse events of mCRPC patients receiving PARPi. Primary outcome was a PSA decline ≥ 50% from baseline. Secondary outcomes were objective response rate, progression-free survival (PFS), radiological PFS, overall survival (OS), conversion of circulating tumor cell count, and time to PSA progression. The number and rate of any grade adverse events (AEs), grade ≥ 3 AEs, and most common grade ≥ 3 AEs were registered. A subanalysis of outcomes per mutation type, prospective trials, and studies adopting combination therapies was performed. Overall, 31 studies were included in this systematic review, 28 of which are available for meta-analysis. The most frequently investigated drug was Olaparib. The most frequent mutation was BRCA2. A PSA decline rate of 43% (95% CI 0.32-0.54) was observed in the overall population. Mean OS was 15.9 (95% CI 12.9-19.0) months. In BRCA2 patients, PSA decline rate was 66% (95% CI 0.57-0.7) and OS 23.4 months (95% CI 22.8-24.1). Half of the patients suffered from grade 3 and 4 AEs (0.50 [95% CI 0.39-0.60]). Most common AEs were hematological, the most frequent being anemia (21.5%). PARP inhibitors represent a viable option for mCRPC patients. Current evidence suggests an increased effectiveness in homologous recombination repair (HRR) gene mutation carriers, especially BRCA2.

Oral chemotherapeutic agents in metastatic hormone-sensitive prostate cancer: A network meta-analysis of randomized controlled trials

Background

Multiple oral chemotherapeutic agents for metastatic hormone-sensitive prostate cancer (mHSPC) have been developed for conjugated use with conventional androgen deprivation therapy (ADT). Several randomized controlled trials (RCTs) report significant benefits in mHSPC patients. Therefore, we compared overall survival (OS) and progression-free survival (PFS) benefits among considerable mHSPC oral chemotherapeutic agents.

Materials and methods

We investigated mHSPC treatment efficacy through a systematic RCT-trial literature review (PubMed, Embase, Web of Science, the Cochrane Library, and Scopus). Two reviewers independently screened, extracted data, and assessed bias risk in duplicate.

Results

We identified 18 RCTs (n = 13,509). Concerning OS, ADT + abiraterone, ADT + abiraterone + docetaxel, ADT + apalutamide, ADT + bicalutamide, ADT + darolutamide + docetaxel, ADT + enzalutamide, ADT + orteronel, and ADT + rezvilutamide were more effective than the standard of care (SOC). Comparing PFS, most treatments were more effective than SOC, excluding ADT + bicalutamide, nilutamide, flutamide, ADT + bicalutamide + palbociclib, and ADT + nilutamide. ADT + docetaxel with androgen receptor targeted agent (ARTA) triplet therapy was not among the top three treatments determined through ranking analysis.

Conclusions

Novel oral chemotherapeutic agent combination therapies must replace current ADT monotherapy and ADT + docetaxel SOC. Even so, ADT + docetaxel with ARTA triplet therapy still is not the best mHSPC treatment and requires further study.