A systematic review and meta-analysis on non-metastatic castration resistant prostate cancer: The radiation oncologist's perspective

Prostate cancer is the second most common cause of cancer-related mortality in men. In patients undergoing a failure after radical treatment, one of the therapeutic option is androgen deprivation: despite initial response rates, a progression to a state of castration resistance is observed in most of the patients. In the present article, we conducted a systematic review and meta-analysis of all clinical trials assessing treatment for nmCRPC with next-generation androgen receptor inhibitors. We performed a review and meta-analysis of phase III randomized controlled trials comparing new agents (apalutamide, enzalutamide, darolutamide) with placebo as control arm, in the setting of nmCRPC. Patients treated with next-generation ARIs had a 26% reduction in the risk of death compared with placebo; compared with other ARIs, darolutamide had the lowest rate of grade 3 and 4 AEs and the lowest therapy discontinuation rate due to any grade AEs. This meta-analysis shows that treatment with new ARIs is safe and significantly reduces the risk of death and of metastasis onset in nmCRPC patients. Under way studies on new biomarkers such as genomic classifiers will probably allow the stratification in more specific subsets of disease. New imaging modalities such as PSMA-PET have shown greater sensibility and specificity than conventional imaging in metastases detection. All patients were randomized in a 2:1 fashion, with a total of 2,694 who underwent next-generation ARIs (806 apalutamide, 955 darolutamide, 933 enzalutamide) and 1,423 in the placebo arm.

Study protocol and preliminary results from a mono-centric cohort within a trial testing stereotactic body radiotherapy and abiraterone (ARTO-NCT03449719)

Background

ARTO trial was designed to evaluate the difference in terms of outcomes between patients affected by oligo metastatic castrate resistant prostate cancer (mCRPC) treated with Abiraterone acetate and randomized to receive or not SBRT on all sites of disease. Here, we present a preliminary analysis conducted on patients enrolled at promoting institution.

Objective

To present a preliminary overview about population features, clinical outcomes, adverse events, quality of life and explorative translational research.

Design, setting, and participants

ARTO (NCT03449719) is a phase II trial including patients affected by oligo mCRPC, randomized to receive standard of care (GnRH agonist or antagonist plus abiraterone acetate 1000 mg and oral prednisone 10 mg daily) with or without SBRT on all metastatic sites of disease. All subjects have < 3 bone or nodal metastases. All patients are treated in I line mCRPC setting, no previous lines of treatment for mCRPC are allowed.

Outcome measurements and statistical analysis

Data about a mono-centric cohort of 42 patients enrolled are presented in the current analysis, with focus on baseline population features, PSA drop at 3 months, biochemical response, and quality of life outcomes. Descriptive statistics regarding translational research are also presented.

Results and limitation

Significant difference in terms of PSA drop at three months was not detected (p = 0.68). Biochemical response (PSA reduction > 50%) was reported in 73.7 versus 76.5% of patients in control vs SBRT arm, respectively (p = 0.84). All patients are alive. Progression occurred in 1 versus 0 patients in the control versus SBRT arm, respectively. After 3 months, an average decrease of 13 points in terms of Global Health Score was reported for the overall population. However, complete recovery was noticed at 6 months. Circulating tumor cells detection rate was 40%.

Conclusions

SBRT + Abiraterone treatment was safe and well tolerated, non-significant trend in terms of PSA drop and biochemical response at 3 months was detected in SBRT arm. Interestingly, CTCs detection in this selected cohort of oligo-mCRPC was lower if compared to historical data of unselected mCRPC patients.

Prospective assessment of AR splice variant and multi-biomarker expression on circulating tumor cells of mCRPC patients undergoing androgen receptor targeted agents: interim analysis of PRIMERA trial (NCT04188275)

Circulating tumor cells detection and ARV7 expression are associated with worse clinical outcomes in metastatic Castration-Resistant Prostate Cancer (mCRPC) undergoing Androgen Receptor Targeted Agents. ARFL, PSMA and PSA may help to refine prognostic models. In our institution, a prospective observational trial testing CTC detection in mCPRC undergoing I line ARTA therapy terminated the planned enrollment in 2020. Here, we present a pre-planned interim analysis with 18 months of median follow-up. RT-qPCR was used to determine the CTC expression of PSA, PSMA, AR and ARV7 before starting ARTA. PSA-drop, Progression-Free and Overall Survival (PFS and OS) and their correlation with CTC detection were reported. Forty-four patients were included. CTC were detected in 43.2% of patients, of whom 8.94% expressed PSA, 15.78% showed ARV7, 63.15% and 73.68% displayed ARFL and PSMA, respectively. Biochemical response was significantly improved in CTC + vs CTC- patients, with median PSA-drop of 18.5 vs 2.5 ng/ml (p = 0.03). After a median follow-up of 18 months, 50% of patients progressed. PFS was significantly longer in CTC- patients (NR vs 16 months). Eight (18.2%) patients died, a non-significant trend in terms of OS was detected in favor of CTC- patients (NR vs 29 months, p = 0.05). AR, PSA and PSMA expression in CTC + had no significant impact on PSA-drop, PFS or OS. PRIMERA-trial confirmed the CTC detection predictive importance in mCRPC patients.

Oligoprogressive castration-resistant prostate cancer treated with metastases-directed stereotactic body radiation therapy: predictive factors for patients' selection

Oligoprogression is defined as limited metastatic clone resistant to on-going systemic treatment that grows in a background of stable or responding systemic disease. Aim of the present study was to analyze oligoprogressive prostate cancer (PC) patients treated with stereotactic body radiation therapy (SBRT) during systemic treatment to identify predictive factors and improve patients' selection. We included PC patients treated with SBRT on a maximum of 3 sites of oligoprogression during systemic therapy. Endpoints were freedom from polymetastatic progression (FPP), local control (LC), distant progression free survival (DPFS), overall survival (OS), and next systemic therapy free survival (NEST-FS). Fifty-three patients were treated on 85 oligoprogressive metastases. Lymph nodes were the most common sites (56.47%), followed by bone (39.29%). Median follow-up was 24.9 months. Rates of FPP at 1- and 2-year were 80.1% and 68.9%, respectively. Median time to polymetastatic progression was 33.7 months. Disease free interval (p = 0.004), site of metastases (p = 0.011), and type of systemic therapy (p = 0.003) were significant for FPP. Switch or intensification of systemic therapy after SBRT was observed in 29 (54.72%) patients with a median NEST-FS of 15.2 months. LC at 1- and 2-year was 94.0% and 92.0%, with PSA doubling time resulted to be significantly associated (p = 0.047). Median DPFS was 8.93 months and median OS was 50.6 months. In conclusion, we confirmed the efficacy of SBRT for oligoprogression from PC, with the potential to prolong the on-going systemic therapy and interrupt the metastatic cascade.

Prospective assessment of AR splice variant and PSMA detection on circulating tumor cells of mCRPC patients: preliminary analysis of patients enrolled in PRIMERA trial (NCT04188275)

In our institution, a prospective observational trial testing micro-RNA (miRNA) and ARV7 mutational status in metastatic, castration resistant prostate cancer (mCRPC), is currently recruiting (PRIMERA trial, NCT04188275). A pre-planned interim analysis was performed when 50% of the planned accrual was reached. In this report, we explored the predictive value of Circulating Tumor Cell (CTC) detection in mCRPC patients undergoing 1st line therapy. Moreover, ARV7, ARFL, PSMA and PSA expression on CTC was reported to explore potential correlation with patient prognosis and response to therapy. PRIMERA is a prospective observational trial enrolling mCRPC patients undergoing standard treatment (ARTA + ADT) after I line ADT failure. Clinical and pathological features were collected. Outcomes selected for this preliminary analysis were time to castration resistance (TTCR), PSA at 8 weeks after ARTA therapy start, PSA drop at 8 weeks, Overall PSA drop, PSA nadir. Correlation between these outcomes and CTC detection was tested. Expression of ARV7, ARFL, PSA and PSMA was explored in CTC+ patients to assess their prevalence in this cohort and their impact on selected outcomes. Median TTCR was significantly shorter in CTC+ vs CTC− patients (32.3 vs 75 months, respectively, p = 0.03) and in ARFL+ vs ARFL− patients (30.2 vs 51.1 months, respectively, p = 0.02). ARV7, PSMA and PSA expression on CTC had no impact on median TTCR, nor on biochemical response to therapy. Patients in whom CTC and ARFL expression were detected had significant reduced TTCR. However, PSA response was not influenced by CTCs detection and specific biomarkers expression.