Outcome of loco-regional radiotherapy in metastatic castration-resistant prostate cancer patients treated with abiraterone acetate

Androgen Receptor Targeted Therapy + Radiotherapy in Metastatic Castration Resistant Prostate Cancer

Objectives

To investigate whether radiotherapy as metastasis-directed therapy (MDT) on oligo-progressive sites in metastatic castration-resistant prostate cancer (mCRPC) patients during treatment with androgen receptor-targeted therapy (ARTT) may lead to control resistant lesions, prolonging ARTT. We analysed progression free survival, overall survival and prognostic parameters that can identify patients that best suit to this approach.

Patients and Methods

Retrospective analysis of a total of 67 lesions in 42 mCRPC patients treated with ablative or palliative RT to oligoprogressive lesions during ARTT. Twenty-eight patients (67%) underwent ARTT with Abiraterone acetate and 14 patients (33%) underwent ARTT with Enzalutamide. Median time between the start of ADT and ARTT beginning was 50.14 months (range 3.37-219 months). We treated 58 lesions (87%) with 3D conformal radiotherapy (3DCRT) and nine lesions (13%) with stereotactic body radiotherapy (SBRT). The Kaplan Meier method was used to assess the median overall survival (OS) and the progression-free survival (PFS).

Results

Median follow-up was 28 months (range 3-82 months). Median OS was 32.5 months (95% CI 25.77-39.16), 1 and 2-year OS were 71.6% and 64.1%, respectively. Median PFS was 19,8 months (95% CI 11.34–28.31), 1 and 2-year PFS were 67.2% and 47.4%, respectively. Median OS for patients that underwent radiotherapy before 6 months from the start of ARTT was 23.4 months (95% CI 2.04-44.89) and 45.5 months (95% CI 31.19-59.8) for patients that underwent radiotherapy after 6 months (p = 0.009).

Conclusion

Local ablative radiation therapy directed to progressive metastasis is a non-invasive, well tolerated treatment with efficacy on prolonging clinical benefit of systemic therapies with ARTT. Patients who underwent RT >6 months from the start of ARTT presented a statistically better OS and PFS compared with patients who underwent radiotherapy <6 months from the start of ARTT.

Recent Development and Future Prospects of Molecular Targeted Therapy in Prostate Cancer

Prostate cancer (PC) is a rapidly increasing ailment worldwide. The previous decade has observed a rapid advancement in PC therapies that was evident from the number of FDA approvals during this phase. Androgen deprivation therapies (ADT) have traditionally remained a mainstay for the management of PCs, but the past decade has experienced the emergence of newer classes of drugs that can be used with or without the administration of ADT. FDA approved poly (ADP-ribose) polymerase inhibitors (PARPi), such as olaparib and rucaparib, after successful clinical trials against gene-mutated metastatic castration-resistant prostate cancer. Furthermore, drugs like apalutamide, darolutamide, and enzalutamide with an androgen-targeted mechanism of action have manifested superior results in non-metastatic castration-resistant prostate cancer (nmCRPC), metastatic castration-sensitive prostate cancer (mCSPC), and metastatic castration-resistant prostate cancer (mCRPC), respectively, with or without previously administered docetaxel. Relugolix, an oral gonadotropin-releasing hormone antagonist, and a combination of abiraterone acetate plus prednisone were also approved by FDA after a successful trial in advanced PC and mCRPC, respectively. This review aims to analyze the FDA-approved agents in PC during the last decade and provide a summary of their clinical trials. It also presents an overview of the ongoing progress of prospective molecules still under trial.

Radiotherapy in nodal oligorecurrent prostate cancer

Objective

The current article encompasses a literature review and recommendations for radiotherapy in nodal oligorecurrent prostate cancer.

Materials and methods

A literature review focused on studies comparing metastasis-directed stereotactic ablative radiotherapy (SABR) vs. external elective nodal radiotherapy (ENRT) and studies analyzing recurrence patterns after local nodal treatment was performed. The DEGRO Prostate Cancer Expert Panel discussed the results and developed treatment recommendations.

Results

Metastasis-directed radiotherapy results in high local control (often > 90% within a follow-up of 1–2 years) and can be used to improve progression-free survival or defer androgen deprivation therapy (ADT) according to prospective randomized phase II data. Distant progression after involved-node SABR only occurs within a few months in the majority of patients. ENRT improves metastases-free survival rates with increased toxicity in comparison to SABR according to retrospective comparative studies. The majority of nodal recurrences after initial local treatment of pelvic nodal metastasis are detected within the true pelvis and common iliac vessels.

Conclusion

ENRT with or without a boost should be preferred to SABR in pelvic nodal recurrences. In oligometastatic prostate cancer with distant (extrapelvic) nodal recurrences, SABR alone can be performed in selected cases. Application of additional systemic treatments should be based on current guidelines, with ADT as first-line treatment for hormone-sensitive prostate cancer. Only in carefully selected patients can radiotherapy be initially used without additional ADT outside of the current standard recommendations. Results of (randomized) prospective studies are needed for definitive recommendations.

Efficacy of PSMA PET-Guided Radiotherapy for Oligometastatic Castrate-Resistant Prostate Cancer

Purpose

To assess the outcome of radiotherapy (RT) to all PSMA ligand positive metastases for patients with castrate-resistant prostate cancer (mCRPC).

Patients and methods

A total of 42 patients developed oligometastatic mCRPC and received PSMA PET-guided RT of all metastases. The main outcome parameters were biochemical progression-free survival (bPFS), and second-line systemic treatment free survival (SST-FS).

Results

A total of 141 PSMA ligand-positive metastases were irradiated. The median follow-up time was 39.0 months (12-58 months). During the follow-up five out of 42 (11.9%) patients died of progressive mPCa. Five out of 42 (11.9%) patients showed no biochemical responses and presented with a PSA level ≥10% of the baseline PSA at first PSA level measurement after RT and were classified as non-responders. The median PSA level before RT was 4.79 ng/mL (range, 0.4-46.1), which decreased significantly to a median PSA nadir level of 0.39 ng/mL (range, <0.07-32.8; p=0.002). The median PSA level at biochemical progression after PSMA ligand-based RT was 2.75 ng/mL (range, 0.27-53.0; p=0.24) and was not significantly different (p=0.29) from the median PSA level (4.79 ng/mL, range, 0.4-46.1) before the PSMA ligand-based RT. The median bPFS was 12.0 months after PSMA ligand PET-based RT (95% CI, 11.2-15.8) and the median SST-FS was 15.0 months (95% CI, 14.0-21.5).

Conclusion

In well-informed and closely followed-up patients, PSMA PET-guided RT represents a viable treatment option for patients with oligometastatic mCRPC to delay further systemic therapies.

Cytoreductive radiotherapy combined with abiraterone in metastatic castration-resistance prostate cancer: a single center experience

Background

To investigate the potential benefit of cytoreductive radiotherapy (cRT) in metastatic castration-resistant prostate cancer (mCRPC) patients receiving abiraterone.

Methods

From February 2014 to February 2019, 149 mCRPC patients treated with abiraterone were identified. Patients receiving cRT before abiraterone failure (AbiRT group) were matched by one-to-two propensity score to patients without cRT before abiraterone failure (non-AbiRT group).

Results

The median follow-up was 23.5 months. Thirty patients (20.1%) were in the AbiRT group, whereas 119 patients (79.9%) were in the non-AbiRT group. The 2-year OS of patients managed by AbiRT and non-AbiRT were 89.5% and 73.5%, respectively (P = 0.0003). On multivariate analysis, only AbiRT (HR 0.17; 95% CI 0.05–0.58; P = 0.004) and prognostic index (HR 2.71; 95% CI 1.37–5.35; P = 0.004) were significant factors. After matching, AbiRT continued to be associated with improved OS (median OS not reached vs. 44.0 months, P = 0.009). Subgroup analysis revealed that patients aged ≤ 65 years (HR 0.09; 95% CI 0.01–0.65; P = 0.018), PSA ≤ 20 ng/mL (HR 0.29; 95% CI 0.09–0.99; P = 0.048), chemotherapy-naïve upon abiraterone treatment (HR 0.20; 95% CI 0.06–0.66; P = 0.008) and in intermediate prognosis groups by COU-AA-301 prognostic index (HR 0.13; 95% CI 0.03–0.57; P = 0.007) had improved OS with AbiRT.

Conclusions

cRT before resistance to abiraterone may improve survival in selected mCRPC patients: age ≤ 65 years old, chemotherapy-naïve, with a relatively low PSA level at the diagnosis of mCRPC and intermediate prognosis.

Metastasis-directed therapy and prostate-targeted therapy in oligometastatic prostate cancer: a systematic review

INTRODUCTION

The aim of this review was to summarize the available evidence on the role of metastasis-directed therapy (MDT) and/or prostate-targeted therapy (PTT) in the setting of oligometastatic prostate cancer (PCa).

EVIDENCE ACQUISITION

We searched PubMed, the Web of Science, and the Cochrane Library databases. The following keywords were used: ("prostate cancer" OR "prostate carcinoma" OR "prostate neoplasm" OR "prostate tumor") AND ("oligometastatic" OR "oligometastasis" OR "PSMA") AND ("surgery" OR "prostatectomy" OR "radical prostatectomy" OR "cytoreductive" OR "local treatment" OR "radiotherapy" OR "stereotactic" OR "stereotaxic") AND ("survival" OR "mortality").

EVIDENCE SYNTHESIS

After evaluating the selection criteria, 81 studies were evaluated for our endpoints. We included 22 studies for PTT of synchronous mPCa. There have been no randomized studies on cytoreductive prostatectomy (cRP). Four prospective studies showed that cRP was feasible but did not contribute to a positive effect on overall survival (OS). Regarding PTT-radiotherapy, two randomized controlled phase 3 trials showed that OS was improved in men with a low metastatic burden. Regarding MDT of metachronous lymph node recurrence, we included 29 retrospective studies. For MDT of oligometastases, we included 30 studies. One randomized phase 2 trial showed that androgen deprivation therapy-free survival improved with stereotactic body radiation therapy compared to that with surveillance; however, benefits on OS remain unclear.

CONCLUSIONS

We performed a comprehensive overview of the current literature on MDT and PTT. The feasibility of MDT and PTT is supported by several retrospective studies. Nevertheless, there remains a lack of high-quality trials to prove its survival benefits. Results from ongoing prospective trials data are awaited.

Safety and Feasibility of Radiation Therapy to the Primary Tumor in Patients With Metastatic Castration-resistant Prostate Cancer

INTRODUCTION

The objective of this study was to evaluate the safety and feasibility of radiation therapy (RT) to the primary tumor in patients with metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

This retrospective study included 105 patients with mCRPC who were treated between April 2004 and May 2019. We divided the patients into 2 groups: patients treated with RT to the primary tumor after they developed CRPC (RT group) and without (non-RT group). The primary purpose was safety assessed using the Common Terminology Criteria for Adverse Events. The secondary purpose included prostate-specific antigen (PSA) response, cancer-specific survival (CSS), and overall survival (OS). Background-adjusted multivariate analyses, with the inverse probability of treatment weighting (IPTW) method, were performed to evaluate impact of RT on CSS and OS.

RESULTS

The median age at CRPC diagnosis was 75 years, and the median follow-up period after CRPC diagnosis was 21 months. The adverse events rates related to RT in any grade and grade ≥ 3 were 55% and 23%, respectively. Nine (29%) patients achieved ≥ 30% PSA decline with RT. In multivariate analyses with the IPTW method, the CSS and OS in the RT group were significantly longer than those in the non-RT group. In subgroup analyses with the IPTW method, RT was significantly associated with improved OS in patients aged ≥ 75 years and patients with initial PSA ≥ 500 ng/mL, cT4, Gleason score ≥ 8, and high-volume metastatic burden.

CONCLUSIONS

RT to the primary tumor is safe and feasible, and it has potential benefits on oncologic outcomes in patients with mCRPC.