Metastasis-directed Therapy Prolongs Efficacy of Systemic Therapy and Improves Clinical Outcomes in Oligoprogressive Castration-resistant Prostate Cancer

Stereotactic ablative radiotherapy for oligoprogressive solid tumours: A systematic review and meta-analysis

INTRODUCTION

The aim of this systematic review and meta-analysis was to review evidence and pool outcomes to assess the effectiveness of stereotactic ablative radiotherapy (SABR) in patients treated for oligoprogressive metastases.

METHODS AND MATERIALS

A search was conducted January 2010 to January 2023 in five bibliographic databases for studies of patients with oligoprogressive disease treated with SABR to all lesions. Clinical outcomes included PFS (progression-free survival), OS (overall survival) and CST (change in systemic therapy). Descriptive statistics were used to summarize the data. Binary random effects model was used for pooled analyses.

RESULTS

12,366 titles/abstracts screened, of which 25 met eligibility criteria and were included the review. All studies were published after 2017 with approximately 80% of the publications in 2021 and 2022. The primary tumour was prostate (n=8, 32%), kidney (n=6, 24%), colorectal (n=4, 16%) followed by breast (n=3, 12%), lung (n=2, 8%) and mixed (n=3, 12%). At 1 year, the pooled PFS was 44% (95% confidence interval [CI]: 34-53%, I2=91%); 53% (95% CI: 45-60%, I2=46%) in prostate, 49% (95% CI: 33-65%, I2=88%) in kidney, 62% (95% CI: 11-113%, I2=96%) in lung, 13% (95% CI: 3-24%, I2=39%) in breast and 30% (95% CI: 19-41%, I2=59%) in mixed.

DISCUSSION

There has been a surge in publications describing the use of SABR in oligoprogressive tumours. Published studies are mostly retrospective reported in prostate and kidney cancers, with limited evidence in other sites. Universal guidelines are recommended to ensure consistency in reporting and comparability of future studies.

Navigating therapeutic sequencing in the metastatic castration-resistant prostate cancer patient journey

BACKGROUND

Novel therapies for metastatic castration-resistant prostate cancer (mCRPC) have improved patient outcomes. However, there is uncertainty on the optimal selection of therapeutic agents for subsequent lines of therapy.

METHODS

We conducted a comprehensive review of published evidence from pivotal clinical trials and recent guidelines for the treatment of mCRPC. We further identify gaps in knowledge and areas for future research.

RESULTS

Key considerations to help guide treatment selection for patients with mCRPC include personal treatment history, individual clinical characteristics, symptoms, prognosis, availability of clinical trials, and other patient-specific factors. Genetic testing and prostate-specific membrane antigen-targeted imaging are important tools to evaluate candidacy for newer therapeutic options such as poly (ADP-ribose) polymerase inhibitors, alone or in combination with androgen receptor pathway inhibitors, and [177Lu]Lu-PSMA-617.

CONCLUSION

This article provides an overview of the evolving treatment landscape of mCRPC, discussing guideline-recommended treatment options and data from key clinical trials, while highlighting ongoing trials that may impact the future treatment landscape. Recommendations for optimal treatment sequencing based on individual patient factors are provided.

Treatment response assessment in mCRPC: is PSMA-PET/CT going to take the lead?

The assessment of response to therapy in prostate cancer (PCa) patients is an ongoing, open issue. Prostate-specific antigen has limitations, especially in advanced metastatic PCa, which often displays intratumor variability in terms of response to therapy. Conventional imaging (i.e. computerized tomography and bone scan) is of limited use for its low sensitivity and specificity. Positron-emission tomography (PET) with prostate-specific membrane antigen (PSMA) demonstrated higher sensitivity and specificity, and novel PSMA-based criteria have been recently proposed for treatment response, with promising results in different scenarios, from chemotherapy to radioligand therapy. PSMA-based criteria have been found to outperform the current RECIST 1.1 and Prostate Cancer Working Group 3 frameworks in describing the behavior of PCa, precisely assessing tumor phenotypes through molecular-imaging-derived parameters. This review critically explores the current evidence about the role of PSMA PET/computed tomography in the assessment of treatment response.

The Role of Local Prostate and Metastasis-Directed Radiotherapy in the Treatment of Oligometastatic Prostate Cancer

Background/Objectives: Oligometastatic prostate cancer (OMPC) represents an early stage of metastatic disease characterized by a limited number of lesions. Recent advancements in imaging and treatment have revived interest in personalized therapies, including metastasis-directed radiotherapy (OMDRT) and primary prostate radiotherapy (PPR). This study evaluates the impact of OMDRT timing and the role of PPR on survival outcomes in OMPC patients; Methods: In this retrospective cohort study, 82 patients with OMPC who underwent OMDRT between 2010 and 2019 were analyzed. Patients were classified based on OMDRT timing (early vs. late) and disease type (synchronous vs. metachronous). Progression-free survival (PFS) and overall survival (OS) were the primary endpoints, assessed via Kaplan-Meier analysis and Cox proportional hazards models; Results: Among the patients, 36 (43.9%) had synchronous and 46 (56.1%) had metachronous OMD. With a median follow-up of 32 months, the 5-year PFS and OS rates were 77.5% and 88.5%, respectively. Early OMDRT significantly improved PFS (HR 0.461, 95% CI: 0.257-0.826, p = 0.009) and OS (HR 0.219, 95% CI: 0.080-0.603, p = 0.003). Subgroup analysis showed the most favorable outcomes for synchronous OMD patients receiving early OMDRT, with a median PFS of 22.2 months and a 5-year survival rate of 42.1%. The treatment of the primary prostate provided a survival benefit in the OS of synchronous OMD patients (5-year 83.1% vs. 50%, p = 0.025), and there was a further improvement in OS after PPR (5-year 87.7% vs. 50%, p = 0.015). Conclusions: Early OMDRT significantly enhances survival outcomes in OMPC, in both synchronous and metachronous cases. The integration of PPR can further improve results, emphasizing the importance of early intervention and personalized treatment strategies. To more definitively clarify our findings across various clinical situations, further studies with larger cohorts or prospective designs are necessary.

Prostate-Specific Membrane Antigen PET/CT-Guided, Metastasis-Directed Radiotherapy for Oligometastatic Castration-Resistant Prostate Cancer

Systemic treatments for metastatic castration-resistant prostate cancer (mCRPC) include androgen deprivation therapy, androgen receptor pathway inhibitors, chemotherapy, and radiopharmaceuticals, all of which have associated toxicity. Prostate-specific membrane antigen (PSMA) PET/CT allows for higher sensitivity in detecting metastatic disease than is possible with conventional imaging. We hypothesized that PSMA PET/CT-guided, metastasis-directed radiotherapy may offer durable disease control with low toxicity rates in patients with mCRPC who have a limited number of metastases. Methods: We retrospectively screened 5 prospective PSMA PET/CT studies for patients with mCRPC who had up to 5 sites of oligorecurrent or oligoprogressive disease on PSMA PET/CT and subsequently received definitive-intent, metastasis-directed radiotherapy to all new or progressing sites with concurrent androgen deprivation therapy. Progression-free survival, freedom from new lines of systemic therapy, and overall survival (OS) were calculated from the start of metastasis-directed radiotherapy using Kaplan-Meier analysis. Biochemical response was defined as at least a 50% decrease in prostate-specific antigen 6 mo after the start of treatment. Toxicity was graded using the Common Terminology Criteria for Adverse Events, version 5. Results: Twenty-four patients met the inclusion criteria with a median follow-up of 33.8 mo (interquartile range, 27.6-45.1 mo). Between October 2017 and April 2023, 11 patients (45.8%) had 1 treated site, 10 patients (41.7%) had 2, and 3 patients (12.5%) had 3. Five sites were prostate or prostate bed, 15 were nodal, 19 were osseous, and 1 was visceral. Seventeen patients (70.8%) continued their preexisting systemic therapy, whereas 7 (29.2%) started a new systemic therapy. Median progression-free survival was 16.4 mo (95% CI, 9.8-23.0 mo). The biochemical response rate was 66.7%. Median freedom from a new line of systemic therapy was 29.0 mo (95% CI, 7.6-50.4 mo). Median OS was not reached. The 2- and 4-y OS rates were 91.1% (95% CI, 79.3%-100%) and 68.8% (95% CI, 45.1%-92.5%), respectively. Grade 2 and grade 3 or higher toxicity rates were 4.2% and 0%, respectively. Conclusion: PSMA PET/CT-guided, metastasis-directed radiotherapy appears to offer durable disease control with low toxicity rates for oligometastatic castration-resistant prostate cancer. Further prospective studies are needed to compare metastasis-directed radiotherapy with systemic therapy versus systemic therapy alone and PSMA PET/CT-guided versus conventional imaging-guided radiotherapy.

HDR brachytherapy versus robotic-based and linac-based stereotactic ablative body radiotherapy in the treatment of liver metastases - A dosimetric comparison study of three radioablative techniques

Purpose

The aim of our study was to compare dosimetric aspects of three radioablation modalities - direct high-dose-rate brachytherapy (HDR-BT) and virtually planned stereotactic body radiation therapy performed on CyberKnife (SBRTck) and Elekta Versa HD LINAC (SBRTe) applied in patients with liver metastases.

Material and methods

We selected 30 patients with liver metastases, who received liver interstitial HDR-BT and virtually prepared plans for SBRTck and SBRTe. In all the cases, the prescribed dose was a single fraction of 25 Gy. Treatment delivery time, doses delivered to PTV and organs at risk, as well as conformity indices, were calculated and compared.

Results

The longest median treatment delivery time was observed in SBRTck in contrast to HDR-BT and SBRTe which were significantly shorter and comparable. HDR-BT plans achieved better coverage of PTV (except for D98%) in contrast to SBRT modalities. Between both SBRT modalities, SBRTck plans resulted in better dose coverage in Dmean, D50%, and D90% values compared to SBRTe without difference in D98%. The SBRTe was the most advantageous considering the PCI and R100%. SBRTck plans achieved the best HI, while R50% value was comparable between SBRTe and SBRTck. The lowest median doses delivered to uninvolved liver volume (V5Gy, V9.1Gy) were achieved with HDR-BT, while the difference between SBRT modalities was insignificant. SBRT plans were better regarding more favourable dose distribution in the duodenum and right kidney, while HDR-BT achieved lower doses in the stomach, heart, great vessels, ribs, skin and spinal cord. There were no significant differences in bowel and biliary tract dose distribution between all selected modalities.

Conclusions

HDR-BT resulted in more favourable dose distribution within PTVs and lower doses in organs at risk, which suggests that this treatment modality could be regarded as an alternative to other local ablative therapies in carefully selected patients' with liver malignancies. Future studies should further address the issue of comparing treatment modalities in different liver locations and clinical scenarios.

Predictive Value of the Prostate-specific Antigen Doubling Time for the Effectiveness of Metastasis-directed Radiotherapy in Patients With Oligometastases After Radical Treatment for Non-metastatic Prostate Cancer

Background/Aim

Data on metastasis-directed radiotherapy (MDRT) are limited, particularly regarding its association with the prostate-specific antigen (PSA) doubling time (PSADT). The present study evaluated the oncological outcomes of MDRT on the basis of the PSADT in oligo-recurrent prostate cancer patients.

Patients and Methods

We retrospectively reviewed clinical data of 35 MDRTs for 29 patients at the Kitasato University Hospital, targeting oligometastatic prostate cancer developed after radical treatment for non-metastatic prostate cancer. Thirty-five MDRTs were classified into the PSADT >3 months (n=25) or PSADT ≤3 months group (n=10). Statistical analyses were performed to compare associations between the two PSADT groups and oncological outcomes such as progression-free survival (PFS) and PSA response after MDRT.

Results

There were no significant differences between the two groups in terms of the clinicopathological features. Kaplan-Meier analysis showed that PFS was significantly better in the PSADT >3 months group than in the PSADT ≤3 months group [median: 13.3 versus (vs.) 2.6 months, p=0.046]. Regarding castration sensitivity, the predictive role of PSADT >3 months was maintained in 21 patients who received MDRT without prior salvage hormone therapy (median PFS: 12.7 vs. 2.6 months, p=0.024). In the castration-resistant setting (n=14), the frequency of a decrease in serum PSA levels after MDRT by 90% was 54.5% (median PFS: 23.1 months).

Conclusion

MDRT can provide benefit especially for patients with PSADT ≥3 months who had oligo-recurrence after the radical treatment for non-metastatic prostate cancer.

Systematic review of the efficacy of stereotactic ablative radiotherapy for oligoprogressive disease in metastatic cancer

BACKGROUND

Stereotactic Ablative Radiotherapy (SABR) for the treatment of oligometastatic disease can improve survival and delay the requirement for systemic therapy. The benefits of SABR in oligoprogressive disease are less well-defined. Here, we evaluate the available evidence investigating the efficacy of SABR in the treatment of oligoprogressive disease.

METHODS

A systematic review was carried out following PRISMA guidelines. Medline and Embase databases were searched using the terms "stereotactic radiotherapy" OR "SABR" OR "Stereotactic Ablative Body Radiotherapy" OR "SBRT" OR "SRT" AND "oligoprogression" in May 2022, June 2023, and February 2024. Studies were excluded where: SABR was used as a radical treatment, a specific oligoprogressive cohort could not be identified, publication was as a conference abstract or where fewer than 10 patients were recruited. Studies treating only brain metastases were also excluded. The site of primary tumour, oligoprogressive sites, rates of overall survival (OS), progression free survival (PFS), local control (LC) and time to next systemic therapy were collected.

RESULTS

Thirty-three full text studies were included. These consisted of single centre and multi-institutional observational studies, case series and phase II trials. Twenty-two studies were related to a specific tumour type: 12 urological cancer (9 prostate, 3 renal cancer), 6 non-small cell lung cancer, 2 colorectal cancer, 2 breast cancer and 11 were studies covering multiple tumour sites (5 studies involving SABR to a single organ and 6 studies involving SABR to multi-organ). Median PFS was >6 months in patients with oligoprogressive prostate, non-small cell lung cancer and renal cancer patients.

CONCLUSIONS

SABR appears to have clinical benefit in oligoprogresssive prostate, lung, and renal patients. However, the optimal management of patients with oligoprogressive disease is still somewhat uncertain due to lack of prospective data. This will hopefully become clearer in the near future with the publication of further randomised trials.

The current landscape of stereotactic body radiation therapy for metastatic castration-resistant prostate cancer

BACKGROUND

The onset of castration-resistance is associated with dismal outcomes in patients with prostate cancer (PCa). Metastasis directed therapy has been investigated in multiple disease settings and may improve outcomes in selected patients. Our systematic review aims to summarize evidence with stereotactic body radiotherapy (SBRT) in castration-resistant prostate cancer (CRPC).

METHODS

The literature search was performed on March 2024, on Pubmed, using the keywords "SBRT" AND "CRPC", and "stereotactic ablative radiotherapy (SABR)" AND "CRPC". This search retrieved a total of 108 articles, 19 were included.

RESULTS

The literature is largely dominated by retrospective series. In men with metachronous oligoprogression, SBRT with androgen receptor pathway inhibitor significantly increased progression-free survival (PFS) including biochemical progression-free survival in a randomized phase II trial (hazard ratio of 0.35, p < 0.001). In patients continuing ADT, the bPFS ranged between 9.5 months to 17.9 months, and next systemic treatment-free survival (NEST-FS) reached up to 2 years. In men with induced oligoprogression, SBRT enabled NEST-FS up to 3 years. SBRT was well tolerated, with less than 5% grade 3 toxicity reported across studies.

CONCLUSION

In the population of patients with oligometastatic CRPC, SBRT enables long-term biochemical response and PFS. In the oligoprogressive setting, SBRT could be integrated to prolong the duration and efficacy of systemic therapies. Nevertheless, the level of evidence remains very low and inclusion within prospective trials remain the preferred option for this population of patients.

Second Chance for Cure: Stereotactic Ablative Radiotherapy in Oligometastatic Disease

PURPOSE

Local ablative therapy, such as radiotherapy or surgery, plays a key role in treatment of patients with oligometastatic disease. Stereotactic ablative body radiotherapy (SABR) comes to the fore as a safe and effective treatment for patients with a limited number of metastases, even those located in hard-to-reach body sites. Many researchers have suggested that metastatsis-directed therapy could improve long-term progression-free survival (PFS) and overall survival (OS) in patients with oligometastases.

PATIENTS AND METHODS

This was a retrospective, single-arm, observational study conducted between July 2015 and February 2022. In our institute, 60 patients with controlled primary tumors and one to five metastases were treated with SABR. Prescribed radiation doses ranged from 12 to 60 Gy administered in one to seven fractions. We aimed to determine whether metastatic-directed therapy using SABR for all oligometastases affects OS and PFS and whether the primary tumor or metastatic site influences OS/PFS.

RESULTS

The most common primary malignancy types were prostate (n = 14), colorectal (n = 10), lung (n = 7), and breast cancers (n = 6). The median follow-up was 30 months, ranging from 9 to 79. The 1-, 3-, and 5-year PFS and OS rates were 54.9%, 37.0%, and 37.0% and 98.3%, 84.4%, and 73.8%, respectively, and the median time to first progression was 15 (range, 2-32) months. Twenty-four (40%) patients had no recurrence. In our analysis, primary tumor site was not an independent prognostic factor. The metastatic site may influence on patient outcome in cases of localized bone and liver metastases.

CONCLUSION

In our retrospective analysis, SABR was associated with favorable levels of PFS and OS in patients with oligometastases. The limitations of our study were lacking high-level evidence, and randomized studies to compare SABR and palliative standard of care are mandatory.

Stereotactic ablative radiation therapy in metastatic prostate cancer

PURPOSE OF REVIEW

The evolving role of stereotactic ablative radiation therapy (SABR) as metastasis-directed therapy (MDT) for oligometastatic prostate cancer (omPCa) will be discussed.

RECENT FINDINGS

Oligometastatic disease (OMD) is an intermediate state between localized and wide-spread malignant disease. OMD has recently been spotlighted given the increasing demonstration of clinical benefit from local therapies despite presence of metastatic disease and allure of the curative potential of MDT in select cases. Among the different forms of MDT, SABR has rapidly become a widely adopted treatment modality. Significant efforts in this space have focused on omPCa, owing to its relatively indolent biology, presence of a sensitive and specific serum biomarker and recent advances in molecular imaging. While most studies have evaluated the role of SABR MDT in hormone sensitive omPCa, new emerging clinical data also suggests benefits of SABR MDT for even castration-resistant disease.

SUMMARY

Treating omPCa with SABR MDT appears to generate an efficacy signal with minimal morbidity across both hormone-sensitive and castration-resistant disease. However, additional definitive omPCa trial data are needed. Future research efforts should investigate biomarkers for this heterogeneous disease space and the role of SABR MDT in combination with systemic agents to improve upon standard of care treatments.

Progression-directed therapy in patients with oligoprogressive castration-resistant prostate cancer

PURPOSE

Oligoprogressive lesions are observed in a subset of patients who progress to castration-resistant prostate cancer (CRPC), while other lesions remain controlled by systemic therapy. This study evaluates the impact of progression-directed therapy (PDT) on these oligoprogressive lesions.

MATERIALS AND METHODS

This retrospective study included 40 patients diagnosed with oligoprogressive CRPC. PDT was performed for treating all progressive sites using radiotherapy. Fifteen patients received PDT using radiotherapy for all progressive sites (PDT group) while 25 had additional first-line systemic treatments (non-PDT group). In PDT group, 7 patients underwent PDT and unchanged systemic therapy (PDT-A group) and 8 patients underwent PDT with additional new line of systemic therapy on CRPC (PDT-B group). The Kaplan-Meier method was used to assess treatment outcomes.

RESULTS

The prostate specific antigen (PSA) nadir was significantly lower in PDT group compare to non-PDT group (p=0.007). A 50% PSA decline and complete PSA decline were observed in 13 patients (86.7%) and 10 patients (66.7%) of PDT group and in 18 patients (72.0%) and 11 patients (44.0%) of non-PDT group, respectively. The PSA-progression free survival of PDT-B group was significantly longer than non-PDT group. The median time to failure of first-line systemic therapy on CRPC was 30.2 months in patients in PDT group and 14.9 months in non-PDT group (p=0.014). PDT-B group showed a significantly longer time to progression than non-PDT group (p=0.025). Minimal PDT-related adverse events were observed.

CONCLUSIONS

PDT can delay progression of disease and enhance treatment efficacy with acceptable tolerability in oligoprogressive CRPC.

Prostate-specific antigen doubling time predicts the efficacy of site-directed therapy for oligoprogressive castration-resistant prostate cancer

Background

In recent years, site-directed therapies (SDTs) targeting progressive lesions in patients with oligometastatic prostate cancer have attracted attention. However, whether they effectively treat oligoprogressive castration-resistant prostate cancer (CRPC) remains unclear. Here, we investigated the efficacy of SDT in patients with oligoprogressive CRPC and identified prognostic factors.

Methods

We reviewed 59 patients with oligoprogressive CRPC who underwent SDT targeting prostate or metastatic lesions between April 2014 and March 2022. We evaluated the associations between several pretreatment clinical variables and treatment procedures and a >50% prostate-specific antigen (PSA) response, progression-free survival (PFS), and time to next treatment (TTNT).

Results

A PSA response of >50% was observed in 66% of patients. The median PFS and TTNT were 8.3 months and 9.9 months, respectively. Patients with PSA doubling time ≥6 months showed a higher >50% PSA response rate (87% vs. 45%; P < 0.001), longer PFS (median, 15.0 vs. 5.0 months; P < 0.001), and longer TTNT (median, 16.3 vs. 5.9 months; P < 0.001) than patients with PSA doubling time <6 months. In multivariate analyses, a PSA doubling time of ≥6 months independently predicted a >50% PSA response, favorable PFS, and TTNT (P = 0.037, 0.025, and 0.017, respectively).

Conclusion

PSA doubling time of ≥6 months may be a key indicator of the favorable efficacy of SDT for oligoprogressive CRPC.

Investigating Nutritional and Inflammatory Status as Predictive Biomarkers in Oligoreccurent Prostate Cancer-A RADIOSA Trial Preliminary Analysis

(1) Background: In the RADIOSA phase II randomized clinical trial (NCT03940235), the biology task entails the identification of predictive and prognostic biomarkers in the context of oligorecurrent, castration-sensitive prostate cancer in order to distinguish polymetastatic from oligometastatic disease. This may lay the groundwork for personalized treatments for those patients who could really benefit from metastasis-directed therapies. (2) Methods: Oligorecurrent PCa pts with three or fewer bone or lymph nodal localizations were randomized 1:1 to receive SBRT alone (arm A) or SBRT + 6 months of ADT (arm B). Common serum-derived biomarkers were collected at baseline, and at 3 months after RT. The prognostic nutritional index, an immune and nutrition-based prognostic score, and the controlling nutritional status (CONUT) score, a scoring system for evaluating patient's nutritional status, were calculated in accordance with the body of available literature. As inflammatory indicators, neutrophil-lymphocyte ratio (NLR) and the NLR-albumin ratio (NLRAR) were assessed. Changes in these parameters between baseline and the 3-month timepoint were evaluated both in absolute and relative values. Changes in these parameters between baseline and the 3-month timepoint were evaluated. Significant differences in the trend of these parameters were assessed using the non-parametric Wilcoxon rank-sum test. A network analysis to analyze the relationships between different features stratifying patients according to the arm of study and site of metastases was performed. (3) Results: The current analysis comprised 88 patients (45 arm A, SBRT only, and 43 arm B, SBRT + ADT). When patients were stratified by ADT administration, cholesterol values showed an increasing trend in the group receiving ADT (p = 0.005) which was no longer significant at 1 year. When patients were stratified by site of metastases (52 lymph nodal, 29 bone localizations), the value of NLR was found to be increased in patients with bone localizations (p < 0.05). In addition, the network analysis showed that BMI and NRI are strongly and directly linked for patients at baseline and that this correlation is no longer found at three months. Finally, when patients were divided according to time from surgery to oligorecurrence (enrollment) the patients with a longer time (>6.7 years) showed an increase in CONUT score from baseline. All the other nutritional and inflammatory scores or parameters investigated in the present analysis showed no statistically significant differences at baseline, three months, 1 year, and in absolute change. (4) Conclusions: The nutritional and inflammatory parameters do not seem to represent valuable candidates for possible use in clinical decision making in our cohort of patients and a reliable biological characterization of the oligometastatic state in prostate cancer still seems far from being achieved. Ongoing molecular analysis will show if there is a role of mutational landscape in the definition of the oligometastatic state.

Stereotactic body radiotherapy in oligoprogressive metastatic castration-resistant prostate cancer during abiraterone or enzalutamide

INTRODUCTION

This monocentric, single-arm, retrospective study investigated the role of stereotactic body radiotherapy in patients with metastatic castration resistant prostate cancer who experienced oligoprogression during androgen receptor targeted agents.

METHODS

We retrospectively enrolled metastatic castration resistant prostate cancer patients treated with androgen receptor targeted agents between December 2016 and January 2022. All patients experienced an oligoprogression (defined as the appearance and/or the progression of ⩽5 bone or nodal or soft tissue metastases) during treatment with androgen receptor targeted agents and received stereotactic body radiotherapy upon oligoprogressive sites, preserving the androgen receptor targeted agents. Further stereotactic body radiotherapy upon new metastatic sites was permitted. Patients showing visceral metastases or receiving palliative radiotherapy were excluded. Progressive disease at >5 metastatic sites or the appearance of visceral metastases led to a change of the systemic treatment. Primary endpoints were 36-month survival rate and 36-month rate of patients receiving treatment with androgen receptor targeted agents. Secondary endpoints were local disease control, biochemical response and safety.

RESULTS

We analyzed data from 30 patients. The 36-month survival rate was 90% (27 patients); 36-month rate of patients who were still on treatment with androgen receptor targeted agents was 50%. 20 of 30 patients had performed imaging control after a single course of stereotactic body radiotherapy: overall response rate was 50%, while clinical benefit was 93%. No ⩾G2 adverse events related to stereotactic body radiotherapy were recorded.

CONCLUSIONS

Stereotactic body radiotherapy in oligoprogressive metastatic sites during androgen receptor targeted agent treatment resulted in a feasible and effective treatment to delay the start of next-line systemic treatment and prolong overall survival in metastatic castration resistant prostate cancer. Longer follow-up and further prospective studies are necessary to confirm our preliminary results.

A case of repeat oligoprogressive castration-resistant prostate cancer treated with pulmonary metastasectomy

Introduction

Several retrospective studies have demonstrated the efficacy of progressive site-directed therapy for oligoprogressive castration-resistant prostate cancer. However, eligible patients for progressive site-directed therapy in these studies were limited to oligoprogressive castration-resistant prostate cancer with bone or lymph node metastases without visceral metastases, and little is known about the efficacy of progressive site-directed therapy for oligoprogressive castration-resistant prostate cancer with visceral metastases.

Case presentation

We report a case with castration-resistant prostate cancer previously treated with enzalutamide and docetaxel, in which only a solitary lung metastasis was identified throughout the course of treatment. The patient underwent thoracoscopic pulmonary metastasectomy with a diagnosis of repeat oligoprogressive castration-resistant prostate cancer. Only androgen deprivation therapy was continued and his prostate-specific antigen levels remained undetectable for 9 months after surgery.

Conclusion

Our case suggests that progressive site-directed therapy may be effective for carefully selected repeat OP-CRPC with a lung metastasis.

A phase II randomized trial of metastasis-directed therapy with alpha emitter radium-223 in men with oligometastatic castration-resistant prostate cancer (MEDAL)

BACKGROUND

The significance of metastasis-directed therapy for oligometastatic prostate cancer has been widely discussed, and targeted therapy for progressive sites is a feasible option as a multidisciplinary treatment for castration-resistant prostate cancer (CRPC). When oligometastatic CRPC with only bone metastases progresses after targeted therapy, it tends to progress as multiple bone metastases. The progression of oligometastatic CRPC after targeted therapy may be due in part to the presence of micrometastatic lesions that, though undetected on imaging, were present prior to targeted therapy. Thus the systemic treatment of micrometastases in combination with targeted therapy for progressive sites is expected to enhance the therapeutic effect. Radium-223 dichloride (radium-223) is a radiopharmaceutical that selectively binds to sites of increased bone turnover and inhibits the growth of adjacent tumor cells by emitting alpha rays. Therefore, for oligometastatic CRPC with only bone metastases, radium-223 may enhance the therapeutic effect of radiotherapy for active metastases.

METHODS

This phase II, randomized trial of Metastasis-Directed therapy with ALpha emitter radium-223 in men with oligometastatic CRPC (MEDAL) is designed to assess the utility of radium-223 in combination with metastasis-directed radiotherapy in patients with oligometastatic CRPC confined to bone. In this trial, patients with oligometastatic CRPC with three or fewer bone metastases on whole-body MRI with diffusion-weighted MRI (WB-DWI) will be randomized in a 1:1 ratio to receive radiotherapy for active metastases plus radium-223 or radiotherapy for active metastases alone. The prior use of androgen receptor axis-targeted therapy and prostate-specific antigen doubling time will be used as allocation factors. The primary endpoint will be radiological progression-free survival against progression of bone metastases on WB-DWI.

DISCUSSION

This will be the first randomized trial to evaluate the effect of radium-223 in combination with targeted therapy in oligometastatic CRPC patients. The combination of targeted therapy for macroscopic metastases with radiopharmaceuticals targeting micrometastasis is expected to be a promising new therapeutic strategy for patients with oligometastatic CRPC confined to bone. Trial registration Japan Registry of Clinical Trials (jRCT) (jRCTs031200358); Registered on March 1, 2021, https://jrct.niph.go.jp/latest-detail/jRCTs031200358.

Serial stereotactic body radiation therapy for oligometastatic prostate cancer detected by novel PET-based radiotracers

BACKGROUND

Radiopharmaceuticals, including Ga-68-prostate specific membrane antigen (PSMA)-11 and F-18-Fluciclovine, are increasingly used to inform therapies for prostate cancer (CaP). Stereotactic body radiation therapy (SBRT) to PET-detected oligometastatic CaP has been shown to improve progression free survival (PFS) and delay androgen deprivation therapy (ADT) compared to observation. For men who subsequently develop oligorecurrent CaP, outcomes following second SBRT are unknown.

METHODS

A retrospective cohort study was conducted. Eligibility criteria included patients with oligometastatic (1-5 lesions) CaP detected on PSMA or Fluciclovine PET who underwent 2 consecutive SBRT courses to tracer-avid sites. Data on stage, tracer type, concurrent systemic therapy, and prostate-specific antigen (PSA) responses for first SBRT (SBRT1) and second SBRT (SBRT2) were collected. Outcomes included PSA decline ≥50% (PSA50), PFS after SBRT2, and ADT initiation or intensification-free survival after SBRT2. Factors potentially associated with PSA50 after SBRT2 was evaluated with multivariable logistic regression. Factors potentially associated with PFS and ADT initiation/intensification-free survival after SBRT2 were evaluated with separate multivariable Cox proportional-hazards models.

RESULTS

Twenty-five patients were identified. At SBRT2, oligorecurrence was detected on PSMA and Fluciclovine PET in 17 (68%) and 8 (32%) patients, respectively. Fifteen (60%) patients had castration-sensitive disease and 10 (40%) had castration-resistant disease. After SBRT2, 16 (64%) achieved a PSA50 response, median PFS was 11.0mo, and median ADT initiation/intensification-free survival was 23.2mo. On multivariable analysis, maximum percent change in PSA after SBRT1 (OR 0.94, 95%CI 0.88-0.99, P = 0.046) and concurrent change in systemic therapy (OR 21.61, 95%CI 1.12-417.9, P = 0.042) were associated with PSA50 responses after SBRT2. PSA50 response after SBRT1 was associated with improved PFS (HR 0.36, 95%CI 0.00-0.42, P = 0.008) and ADT initiation/intensification-free survival (HR 0.07, 95%CI 0.01-0.68, P = 0.021) after SBRT2. From SBRT1 to last follow-up (median 48 months), 7 (28%) patients remained ADT-free.

CONCLUSIONS

Serial SBRT for oligometastatic CaP detected on PSMA or Fluciclovine PET is feasible and can achieve PSA declines, with or without systemic therapy. Degree of biochemical response to first SBRT warrants further study as a potential predictor of PSA response, PFS, and ADT initiation/intensification-free survival following a subsequent SBRT course. This preliminary evidence provides rationale for larger, prospective studies of this strategy.

The P2 purinoceptors in prostate cancer

P2 purinoceptors are composed of ligand-gated ion channel type (P2X receptor) and G protein-coupled metabolite type (P2Y receptor). Both these receptors have played important roles in the prostate cancer microenvironment in recent years. P2X and P2Y receptors can contribute to prostate cancer's growth and invasiveness. However, the comprehensive mechanisms have yet to be identified. By summarizing the relevant studies, we believe that P2X and P2Y receptors play a dual role in cancer cell growth depending on the prostate cancer microenvironment and different downstream signalling pathways. We also summarized how different signalling pathways contribute to tumor invasiveness and metastasis through P2X and P2Y receptors, focusing on understanding the specific mechanisms led by P2X4, P2X7, and P2Y2. Statins may reduce and prevent tumor progression through P2X7 so that P2X purinergic receptors may have clinical implications in the management of prostate cancer. Furthermore, P2X7 receptors can aid in the early detection of prostate cancer. We hope that this review will provide new insights for future mechanistic and clinical investigations into the role of P2 purinergic receptors in prostate cancer.

Patterns of recurrence in genuine and induced oligometastatic castration-resistant prostate cancer treated with progressive site-directed therapy

OBJECTIVES

To describe oncological outcomes after progressive site-directed therapy (PSDT) in genuine and induced oligometasatic (OM)-castration-resistant prostate cancer (CRPC).

METHODS

Thirty-seven patients with OM-CRPC treated with PSDT were retrospectively analyzed, and oncological outcomes and recurrence patterns on whole-body diffusion-weighted MRI (WB-DWI) were evaluated.

RESULTS

Twenty-two (59%) were classified as genuine OM-CRPC and 15 (41%) as induced OM-CRPC. A 50% decline in PSA after PSDT was observed in 21 (95%) genuine OM-CRPCs and 7 (47%) induced OM-CRPCs (p = 0.0005). At a median observation period of 7.3 months, median PSA progression-free survival were 10.9 months in the genuine OM-CRPCs and 4.8 months in the induced OM-CRPCs (p = 0.015). Among the patients who developed PSA progression after PSDT, 11 of 15 in the genuine OM-CRPCs (73%) and 11 of 14 in the induced OM-CRPCs (79%) underwent WB-DWI at PSA progression. The median numbers of newly detected metastases were 2 (range: 1-5) in the genuine OM-CRPCs and 4 (range: 1-40) in the induced OM-CRPCs (p = 0.049). Only one new metastasis appeared in 5 patients from the genuine OM-CRPCs (46%) and 1 from the induced OM-CRPCs (9.1%, p = 0.048). In 7 of 9 patients from the genuine OM-CRPCs (78%) and 7 of 8 patients from the induced OM-CRPCs (88%) who had bone metastases alone, the newly detected metastasis limited to the bone.

CONCLUSIONS

Genuine OM-CRPC had better oncological outcomes after PSDT than induced OM-CRPC, and the number of lesions detected at recurrence was limited. Induced OM-CRPC might be a disseminated condition with micrometastases at OM diagnosis.

Prostate and metastasis-directed focal therapy in prostate cancer: hype or hope?

INTRODUCTION

The paradigm of focal therapy's role in metastatic patients is being challenged by evolving attitudes and emerging data. At the current time, specifically regarding prostate cancer, does the evidence indicate this is more hype or hope?

AREAS COVERED

We searched the literature via PubMed, MEDLINE, and Embase for studies from 2014 to the present addressing focal therapy with non-palliative intent in metastatic prostate cancer patients, emphasizing prospective trials when available. We sought to address all common clinical scenarios: de novo synchronous diagnosis, oligorecurrence, oligoprogression, and mCRPC disease.

EXPERT OPINION

Current evidence is strongest, and in our opinion practice-changing, for prostate-directed RT in de novo metastatic patients with low metastatic burden. Metastasis-directed therapy with SBRT is consistently shown to have low rates of toxicity, and promising rates of ADT-free survival and progression-free survival. These can be utilized on a patient-by-patient basis with these endpoints in mind, but do not yet show sufficient benefit to be standard of care. This is a rich area of ongoing research, and many trials should publish in the coming years to shed light on many unanswered questions, including the role of cytoreductive prostatectomy, systemic therapy combined with MDT, and the integration of modern PET imaging.

Using PSMA imaging for prognostication in localized and advanced prostate cancer

The use of prostate-specific membrane antigen (PSMA)-directed applications in modern prostate cancer management has evolved rapidly over the past few years, helping to establish new treatment pathways and provide further insights into prostate cancer biology. However, the prognostic implications of PSMA-PET have not been studied systematically, owing to rapid clinical implementation without long follow-up periods to determine intermediate-term and long-term oncological outcomes. Currently available data suggest that traditional prognostic factors and survival outcomes are associated with high PSMA expression (both according to immunohistochemistry and PET uptake) in men with localized and biochemically recurrent disease. Treatment with curative intent (primary and/or salvage) often fails when PSMA-positive metastases are present; however, the sensitivity of PSMA-PET in detecting all metastases is poor. Low PSMA-PET uptake in recurrent disease is a favourable prognostic factor; however, it can be associated with poor prognosis in conjunction with high ¹⁸F-fluorodeoxyglucose uptake in metastatic castration-resistant prostate cancer. Clinical trials embedding PSMA-PET for guiding management with reliable oncological outcomes are needed to support ongoing clinical use.

Recommendations for radiation therapy in oligometastatic prostate cancer: An ESTRO-ACROP Delphi consensus

BACKGROUND AND PURPOSE

Oligometastatic prostate cancer is a new and emerging treatment field with only few prospective randomized studies published so far. Despite the lack of strong level I evidence, metastasis-directed therapies (MDT) are widely used in clinical practice, mainly based on retrospective and small phase 2 studies and with a large difference across centers. Pending results of ongoing prospective randomized trials, there is a clear need for more consistent treatment indications and radiotherapy practices.

MATERIAL AND METHODS

A European Society for Radiotherapy and Oncology (ESTRO) Guidelines Committee consisting of radiation oncologists' experts in prostate cancer was asked to answer a dedicated questionnaire, including 41 questions on the main controversial issues with regard to oligometastatic prostate cancer.

RESULTS

The panel achieved consensus on patient selection and routine use of prostate-specific membrane antigen positron emission tomography (PSMA PET) imaging as preferred staging and restaging imaging. MDT strategies are recommended in the de novo oligometastatic, oligorecurrent and oligoprogressive disease setting for nodal, bone and visceral metastases. Radiation therapy doses, volumes and techniques were discussed and commented.

CONCLUSION

These recommendations have the purpose of providing standardization and consensus to optimize the radiotherapy treatment of oligometastatic prostate cancer until mature results of randomized trials are available.

Stereotactic body radiotherapy to defer systemic therapy in patients with oligorecurrent disease

•

SBRT may be used to defer systemic therapy in patients with oligorecurrence.

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Low rates of systemic therapy after SBRT for all oligorecurrent lesions were observed.

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Patients had favorable OS and few treatment-related toxicities.

•

New metastases were treated with repeat SBRT in 33.8% of patients.

•

Fewer lines of systemic therapy and a low baseline tumor volume were associated with longer systemic therapy-free interval.

Background

Patients who develop oligorecurrent disease may be treated with metastasis-directed stereotactic body radiotherapy (SBRT) to defer the start of systemic therapy and delay its potential side effects. We report oncological outcomes and patterns of failure in patients with oligorecurrent disease treated with SBRT and determine which factors impact the interval to initiation of systemic therapy.

Material/Methods

This retrospective study included patients with oligorecurrent disease (≤5 lesions) from any solid organ malignancy, treated with SBRT to all metastases and no systemic therapy for a minimum one month after SBRT between 01/2014 and 12/2019. The Kaplan-Meier method was used to analyze overall survival (OS) and progression-free survival (PFS), and the cumulative incidence of initiation of systemic therapy was analyzed assuming death without systemic therapy as a competing risk. Univariable and multivariable analyses are used to assess predictors of the systemic therapy-free interval.

Results

Among 545 patients treated with SBRT for oligometastatic disease, 142 patients were treated with SBRT only for oligorecurrent disease. The most common primary tumors were lung and gastrointestinal cancer in 47 (33.1 %) and 28 (19.7 %) patients, respectively. After a median follow-up of 25 months, the median PFS and OS was 6.1 months and 48.9 months, respectively. Distant metastases were the most common first failure, and oligometastatic distant failure occured in 86 patients (60.6 %). New metastases were treated with repeat SBRT in 48 patients (33.8 %). The 1- and 2-year cumulative incidence of initiation of systemic therapy was 24.6 % and 36.8 %, respectively. In multivariable analysis, the number of previous lines of systemic therapy and the cumulative volume of metastases were significantly associated with the interval to initiation of systemic therapy.

Conclusion

Selected patients with oligorecurrence achieved favorable OS and low cumulative incidence of initiation of systemic therapy. Prospective studies are warranted to determine how the deferral of systemic therapy impacts OS compared with immediate systemic therapy in combination with SBRT.

Role of Local Treatment for Oligometastasis: A Comparability-Based Meta-Analysis

PURPOSE

We intend to investigate the oncological efficacy and feasibility of local consolidative therapy (LCT) through a meta-analysis method.

MATERIALS AND METHODS

Four databases including PubMed, MEDLINE, Embase, and Cochrane library were searched. Target studies are controlled trials comparing outcomes of LCT versus a control group. Primary endpoints are overall survival (OS) and progression-free survival (PFS).

RESULTS

A total of 54 studies involving 7,242 patients were included. Pooled analyses showed that the LCT arm could achieve improved OS with pooled odds ratio of 2.896 (95% confidence interval [CI], 2.377 to 3.528; p < 0.001). Regarding PFS, pooled analyses showed pooled odds ratio of 3.045 (95% CI, 2.356 to 3.937; p < 0.001) in favor of the LCT arm. In the subgroup analyses including the studies with reliable comparability (e.g. randomized studies or intentionally matched studies without significant favorable prognosticator in LCT arms), pooled odds ratio was 2.548 (95% CI, 1.808 to 3.591; p < 0.001) favoring the LCT arm regarding OS. Regarding PFS, pooled OR was 2.656 (95% CI, 1.713 to 4.120; p < 0.001) which also favored the LCT arm. Subgroup analyses limited to the randomized controlled trials (RCT) were also performed and pooled odds ratios on OS and PFS were 1.535 (95% CI, 1.082 to 2.177; p=0.016) and 1.668 (95% CI, 1.187 to 2.344; p=0.003). The rates of grade ≥ 3 complications related to LCT was mostly low (< 10%) and not significantly higher compared to the control arm.

CONCLUSION

Pooled analyses results of all included studies, selected studies with reliable comparability, and RCT's demonstrated the survival benefit of LCT. These consistent results suggest that LCT was beneficial to the patients with oligometastasis.

Nodal and osseous oligometastatic prostate cancer: a cohort including the introduction of PSMA-PET/CT-guided stereotactic and hypofractionated radiotherapy with elective nodal therapy

PURPOSE

Oligometastatic prostate cancer is heavily investigated, and conventionally fractionated elective nodal treatment appears to increase biochemical relapse-free (bRFS) survival. The novelty of this report is to present elective nodal radiotherapy (ENRT) with simultaneous integrated boost with stereotactic (SBRT) or hypofractionated radiotherapy (HoFRT) for tolerance and for bRFS which we compared with SBRT of the involved field (IF) only.

MATERIALS AND METHODS

Patients between 2018 and 2021 with and oligometastatic prostate cancer treated with SBRT or hypofractionation were eligible. A radiobiologically calculated simultaneous integrated boost approach enabled to encompass elective nodal radiotherapy (ENRT) with high doses to PSMA-positive nodes. A second group had only involved field (IF) nodal SBRT.

RESULTS

A total of 44 patients with 80 lesions of initially intermediate- (52%) or high-risk (48%) D'Amico omPC were treated with SBRT to all visible PSMA-PET/CT lesions and 100% of the treated lesions were locally controlled after a median follow-up was 18 months (range 3-42 months). Most lesions (56/80; 70%) were nodal and the remainder osseous. Median bPFS was 16 months and ADT-free bPFS 18 months. ENRT (31 patients) versus IF (13 patients) prevented regional relapse more successfully. At univariate analysis, both initial PSA and length of the interval between primary diagnosis and biochemical failure were significant for biochemical control. Treatment was well tolerated and only two patients had toxicity ≥ grade 3 (1 GU and 1 GI, each).

DISCUSSION/CONCLUSION

SBRT and hypofractionated radiotherapy at curative doses with ENRT was more effective to delay ADT than IF, controlled all treated lesions and was well tolerated.

Radiotherapy in Oligometastatic Prostate Cancer

Prostate cancer ranges from localized, low risk to metastatic, morbid disease. While radiotherapy is commonly incorporated in the treatment of early disease or for palliation of symptomatic lesions, its role in extending survival in metastatic disease is less well-established. Here, we review the available evidence surrounding localized radiotherapy in the presence of oligometastatic disease and metastasis-directed therapy in both hormone-sensitive and hormone-resistant prostate cancer. We further outline potential future incorporation of radiotherapy as an immune-sensitizing therapy and the importance of highly sensitive imaging modalities in considering radiotherapy in metastatic disease.

Patient and Treatment Factors Associated with Improved Local Control and Survival in Oligometastatic Bone Disease: Results from a Large Single-Institution Experience Using Stereotactic Body Radiation Therapy

PURPOSE

Limited data exists to guide optimal patient selection and treatment of bone metastases with curative intent despite the increasing application of stereotactic body radiation therapy (SBRT) for oligometastatic (OM) disease control and re-irradiation(ReRT).

METHODS

Clinical characteristics for 434 patients consecutively treated with bone SBRT at a single institution from 3/2011-6/2020 were analyzed by OM, spine, and non-spine bone using Cox regression to determine association with local control (LC), progression-free survival (PFS), and overall survival (OS), and the Kaplan-Meier method to estimate PFS and OS.

RESULTS

Most patients had prostate (39%) or breast/lung (21%) cancer and 1-3 lesions (96%), with 651 lesions (spine 63%) treated for ReRT (12%) or OMD (88%), including synchronous (10%), metachronous (28%), repeat (27%), or induced (23%) states as defined by ESTRO/EORTC criteria. Biologically effective dose (BED₁₀) ≥50 (HR 0.68, CI 0.48-0.96, p<0.03) predicted improved LC among OM lesions and planning target volume (PTV)≥150 cc (HR 1.94, CI 1.02 to 3.70, p<0.04) predicted worse LC for non-spine bone. Prostate histology, performance status (PS) 0-1, and MFI ≥2 year predicted improved PFS and OS (p<0.05). Metachronous, synchronous, or repeat OM had higher PFS and OS (p≤0.001) than induced OM. With median follow-up 25.7 months, 1 and 2-year PFS was 63% and 47% for OM and 36% and 25% for ReRT;1 and 2-yr OS was 87% and 73% for OM, 58% and 43% for ReRT. Acute toxicities included grade 1-2 pain flare (9%) and fatigue (14%). Late toxicities included fracture (1%) for OM and myelopathy (2.5%) or nerve pain (1.2%) for ReRT.

CONCLUSIONS

BED₁₀ ≥ 50 for OM and PTV<150cc for non-spine bone lesions was associated with improved LC. Prostate histology, PS 0-1, MFI≥2 years, and metachronous, synchronous, or repeat presentations per EORTC/ESTRO OM criteria predicted improved PFS and OS among OM patients treated with bone SBRT.

Radiotherapy in Oligometastatic, Oligorecurrent and Oligoprogressive Prostate Cancer: A Mini-Review

Globally, prostate cancer is one of the most common malignancies affecting men. With the advent of advanced molecular imaging, an increasing number of men are found to have oligometastatic disease (OD) either at primary diagnosis or at the time of biochemical failure. No strict definition exists for OD, with historical and ongoing studies utilizing diverse criteria. There is mounting evidence from many different malignancies that patients with OD have improved outcomes compared to their widely metastatic counterparts. As such, treatment intensification of those with OD or oligoprogressive disease has become an area of intense interest and study. This article will review the biology, evidence and controversy behind the treatment of de novo oligometastatic, oligorecurrent and oligoprogressive prostate cancer.

How PET-CT is Changing the Management of Non-metastatic Castration-resistant Prostate Cancer?: Comment la TEP-TDM Peut Modifier la Prise en Charge du Cancer de la Prostate Non Métastatique Résistant à la Castration ?

INTRODUCTION

The aim of this narrative review conducted by the Prostate Cancer Committee of the French Association of Urology (CC-AFU) was to provide an update on the current evidence for the impact of PET/CT in the management of men with non-metastatic castration-resistant prostate cancer (nmCRPC).

MATERIAL AND METHODS

This review is based on data available in the literature on PET/CT imaging for staging nmCRPC patients. A PubMed search and narrative review of the data were performed in March 2022. Only articles in French or English were considered.

RESULTS

Current guidelines recommend bone scan and CT scan as standard imaging modalities for staging and follow-up of patients with nmCRPC. Nearly one-third of asymptomatic patients with presumed nmCRPC ultimately have metastatic disease on conventional imaging. Increasing reports have shown that conventional imaging has limited accuracy in detecting metastatic disease in nmCRPC patients, leading to the development of next-generation imaging techniques. In a retrospective study, 18F-choline PET/CT detected distant metastases in 27/58 high-risk nmCRPC patients with prior negative conventional imaging. The implementation of radiolabeled ligands of the prostate-specific membrane antigen (PSMA) PET/CT in staging strategy has resulted in metastasis detection in 45% to 98% of patients with presumptive nmCRPC on conventional imaging. Such an early diagnosis of metastatic CRPC may allow patients to be referred for metastasis-directed therapies (i.e. stereotactic body radiotherapy), aimed at prolonging the efficacy of systemic therapies and improving clinical outcomes. However, current data are not strong enough to recommend this strategy, which must be properly evaluated in clinical trials. Indeed, the use of molecular imaging may lead to inappropriate undertreatment if the second-generation androgen receptor inhibitors (darolutamide, enzalutamide, apalutamide), which prolong life, are not used in the subgroup of patients with high PSA velocity (PSA doubling time <10 months).

CONCLUSION

Implementation of PSMA-PET/CT in the staging strategy would result in a migration of disease stage to extra-pelvic, M1 disease in at least half of presumed nmCRPC patients. The unprecedented accuracy of PSMA-PET/CT may pave the way for a more personalized treatment strategy. However, no data yet support this strategy for all nmCRPC patients as no oncologic benefit of early detection of M1 disease or MDT has been demonstrated. © 2022 Elsevier Masson SAS. All rights reserved.

Better survival of patients with oligo- compared with polymetastatic cancers: a systematic review and meta-analysis of 173 studies

Background: The modern concept of oligometastatic (OM) state has been initially developed to describe patients with a low burden of disease and with a potential for cure with local ablative treatments. We systematically assessed the risk of death and relapse of oligometastatic (OM) cancers compared to cancers with more diffuse metastatic spread, through a meta-analysis of published data. 

Methods: PubMed, the Cochrane Library, and EMBASE were searched for studies reporting prognosis of patients with OM solid tumors. Risk of death and relapse were extracted and pooled to provide an adjusted hazard ratio with a 95% confidence interval (HR 95%CI).  The primary outcome of the study refers to overall mortality in OM vs. polymetastatic (PM) patients. 

Results. Mortality and relapse associated with OM state in patients with cancer were evaluated among 104,234 participants (n=173 studies). Progression-free survival was better in patients with OM disease (hazard ratio [HR] = 0.62, 95% CI 0.57–0.68; P <.001; n=69 studies). Also, OM cancers were associated with a better overall survival (OS) (HR = 0.65, 95% CI 0.62-0.68; P<.01; n=161 studies). In colorectal (CRC), breast, non-small cell lung cancer (NSCLC) and renal cell carcinoma (RCC) the reduction in the risk of death for OM patients were 35, 38, 30 and 42%, respectively. Biliary tract and cervical cancer do not significantly better in OM stage likely for paucity of data.

Conclusions. Patients with OM cancers have a significantly better prognosis than those with more widespread stage IV tumors. In OM cancer patients a personalized approach should be pursued.

Survival Outcomes and Pattern of Relapse After SABR for Oligometastatic Prostate Cancer

Introduction

The addition of stereotactic ablative radiotherapy (SABR) to standard of care for patients with oligometastatic prostate cancer has the potential of improving survival and delaying further metastases. The primary aim of this analysis is to report survival outcomes and pattern of recurrence of patients with hormone-sensitive (HSPC) and castrate-resistant (CRPC) oligometastatic prostate cancer treated with SABR.

Methods

This is a single-center retrospective study of patients with oligometastatic prostate cancer treated in Iridium Network between 2014 and 2018. All patients with oligometastatic (≤3 active lesions) HSPC and CRPC treated with SABR were included. Data were collected using electronic records. Patterns of first progression following SABR were reported. Kaplan-Meier methods were used to determine survival outcomes.

Results

Eighty-seven men received SABR to 115 metastases. Nineteen patients were castrate-resistant and 68 hormone-sensitive at the time of SABR. Median follow-up was 41.6 months. In 25% of patients, no decline from baseline PSA was recorded. Median bPFS was 11.7 months (95% CI 7.6 - 18.3) for HSPC as well as CRPC (95% CI 6.4 - 24.0) (p=0.27). Median DMFS was 21.8 (95% CI 16.9 - 43.2) versus 17.6 months (95% CI 6.7 - 26.2) for HSPC versus CRPC, respectively (p=0.018). Median OS was 72.6 months (95% CI 72.6 - not reached) for HSPC and not reached for CRPC (95% CI 35.4 months - not reached) (p=0.026). For the subgroup of oligorecurrent HSPC, short-term androgen-deprivation therapy was associated with improved bPFS (median 6.0 vs. 18.3 months, HR 0.31, p<0.001) and DMFS (median 15.8 vs 29.6 months, HR 0.5, p=0.06). Information on pattern of relapse was retrieved for 79 patients: 45% (36/79) of these patients were long-term disease-free (>18 months), 28% (22/79) of patients wmere oligoprogressive (≤3 new lesions) and 27% (21/79) developed a polymetastatic relapse.

Conclusion

In this cohort, oligometastatic HSPC showed potential benefit from SABR with a median DMFS of 21.8 months. Well-selected patients with oligometastatic CRPC may also benefit from SABR. For patients with metachronous and repeat oligorecurrent HSPC, combining SABR with short-term androgen-deprivation therapy was associated with improved bPFS and DMFS. Overall, 36/87 (41%) of patients were still free from clinical relapse at 18 months.

Stereotactic radiotherapy for oligometastases in the lymph nodes

Even though systemic therapy is standard treatment for lymph node metastases, metastasis-directed stereotactic radiotherapy (SRT ) seems to be a valid option in oligometastatic patients with a low disease burden.

Positron emission tomography-computed tomography (PET-CT ) is the gold standard for assessing metastases to the lymph nodes; co-registration of PET-CT images and planning CT images are the basis for gross tumor volume (GTV ) delineation. Appropriate techniques are needed to overcome target motion. SRT schedules depend on the irradiation site, target volume and dose constraints to the organs at risk (OARs) of toxicity. Although several fractionation schemes were reported, total doses of 48–60 Gy in 4–8 fractions were proposed for mediastinal lymph node SRT, with the spinal cord, esophagus, heart and proximal bronchial tree being the dose limiting OAR s. Total doses ranged from 30 to 45 Gy, with daily fractions of 7–12 Gy for abdominal lymph nodes, with dose limiting OARs being the liver, kidneys, bowel and bladder. SRT on lymph node metastases is safe; late side effects, particularly severe, are rare.

Stereotactic Radiotherapy for Lesions Detected via 68Ga-Prostate-specific Membrane Antigen and 18F-Fluorodexyglucose Positron Emission Tomography/Computed Tomography in Patients with Nonmetastatic Prostate Cancer with Early Prostate-specific Antigen Progression on Androgen Deprivation Therapy: A Prospective Single-center Study

BACKGROUND

Dual-tracer positron emission tomography/computed tomography (PET/CT) with a ⁶⁸Ga-labelled prostate-specific membrane antigen (PSMA) ligand and ¹⁸F-fluorodeoxyglucose (FDG) improves detection of metastatic heterogeneity and burden in patients with nonmetastatic prostate cancer (nmPCa). However, there is limited prospective evidence regarding its impact on the efficacy of stereotactic body radiotherapy (SBRT).

OBJECTIVE

To evaluate metastasis-free survival (MFS) and toxicity after SBRT to dual-tracer PET/CT-detected metastases in patients with nmPCa and early prostate-specific antigen (PSA) progression on androgen deprivation therapy (ADT; PSA ≤2 ng/ml).

DESIGN, SETTING, AND PARTICIPANTS

Patients were prospectively screened using dual-tracer PET/CT between April 2019 and October 2020. SBRT was recommended for patients with five or fewer nonvisceral metastases (SBRT group). Patients without detectable metastases (N-/M- group) and those who refused SBRT (ADT group) continued to receive ADT. Patients were followed with conventional imaging.

INTERVENTION

SBRT to each PET/CT-detected metastasis.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Kaplan-Meier methods were used to determine MFS. Toxicity was evaluated using Common Terminology Criteria for Adverse Event v4.0.

RESULTS AND LIMITATIONS

Seventy-four consecutive patients were screened. The median PSA and PSA doubling time were 0.59 ng/ml and 4.56 mo, respectively. Overall, 54 patients had metastases and 17 had PSMA-/FDG+ disease. Seven patients were excluded from the MFS analysis, including two with a history of abiraterone treatment and five with more than five metastases. The median follow-up was 21.4 mo. The ADT group had shorter MFS than the SBRT group (11.0 mo vs not reached; hazard ratio [HR] 4.69, 95% confidence interval [CI] 2.92-25.0; p < 0.001) and the N-/M- group (11.0 mo vs not reached; HR 8.78, 95% CI 4.04-40.30; p < 0.001). There was no significant difference in median MFS between the SBRT group and the N-/M- group (p = 0.261). A PSA response >90% was achieved by 86% of patients in the SBRT group. There were no grade ≥3 adverse events after SBRT. The nonrandomized design is the major study limitation.

CONCLUSIONS

Dual-tracer PET/CT-guided SBRT delivered superior local control rates in comparison to ADT alone and had minimal toxicity.

PATIENT SUMMARY

We investigated metastasis-targeted radiotherapy for patients with up to five prostate cancer metastases detected with two different radioisotope scans. Our results show that this approach yields promising metastasis-free survival and low toxicity.

Stereotactic Body Radiation Therapy in Patients with Oligometastatic Disease: Clinical State of the Art and Perspectives

Stereotactic body radiation therapy (SBRT) is a form of radiation therapy (RT) in which a small number of high doses of radiation are delivered to a target volume using highly sophisticated equipment. Stereotactic body radiation therapy is crucial in two cancer stages: early primary cancer and oligometastatic disease, with the goal of inducing complete cancer remission in both. This treatment method is commonly used to treat a variety of disease types. Over the years, a growing body of clinical evidence on the use of SBRT for the treatment of primary and metastatic tumors has accumulated, with efficacy and safety demonstrated in randomized clinical trials. This article will review the technical and clinical aspects of SBRT according to disease type and clinical indication.

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.

Impact of Progressive Site-Directed Therapy in Oligometastatic Castration-Resistant Prostate Cancer on Subsequent Treatment Response

Simple Summary

Local treatment for oligometastatic hormone-naive prostate cancer has been shown to be effective in phase II trials. As for the efficacy of targeted therapy for oligometastatic castration-resistant prostate cancer, the results of the phase trial are not yet available, but the number of reports showing efficacy by retrospective analysis is increasing. Progressive site-directed therapy has been shown to delay the next intervention and prolong progression-free survival, but its impact on subsequent treatment efficacy and contribution to overall survival has not been reported. The purpose of this retrospective study is to evaluate the impact of progressive site-directed therapy for oligometastatic castration-resistant prostate cancer on the subsequent treatment outcomes. We found that progressive site-directed therapy was associated with better response to subsequent androgen receptor axis-targeted drugs and better overall survival. Progressive site-directed therapy for oligometastatic castration-resistant prostate cancer may improve subsequent oncological outcomes.

Abstract

The purpose of this study was to evaluate the impact of progressive site-directed therapy (PSDT) for oligometastatic castration-resistant prostate cancer (OM-CRPC) on the efficacy of subsequent androgen receptor axis-targeted (ARAT) drugs, and to demonstrate the possibility of prolonging overall survival (OS). We performed a retrospective analysis of 15 OM-CRPC patients who underwent PSDT and subsequently received first-line ARAT drugs (PSDT group) and 13 OM-CRPC patients who were treated with first-line ARAT drugs without PSDT (non-PSDT group). PSDT was performed with the intention of treating all progressing sites detected by whole-body diffusion-weighted MRI with radiotherapy. Thirteen patients (86.7%) treated with PSDT had a decrease in PSA levels, which was at least 50% in 10 (66.7%) patients. The median PSA progression-free survival (PFS) for PSDT was 7.4 months. The median PSA-PFS for ARAT was 27.2 months in patients in the PSDT group and 11.7 months in the non-PSDT group, with a significant difference between the two groups (hazard ratio [HR], 0.28; p = 0.010). The median OS was not reached in the PSDT group and was significantly longer than 44.5 months in the non-PSDT group (HR, 0.11; p = 0.014). In OM-CRPC, PSDT may improve the efficacy of subsequent ARAT and OS.

Evaluating the Role of Stereotactic Body Radiation Therapy With Respect to Androgen Receptor Signaling Inhibitors for Oligometastatic Prostate Cancer

Purpose

Outcomes of stereotactic body radiation therapy (SBRT) with respect to androgen receptor signaling inhibitors (ARSI) have not been characterized for oligometastatic prostate cancer. We sought to characterize prostate specific antigen (PSA) response and progression-free survival (PFS) after SBRT among men who have progressed on ARSI therapy in the oligometastatic castration-resistant setting.

Methods and Materials

A single-institution retrospective analysis was performed for men with ARSI-resistant, oligometastatic, castrate-resistant prostate cancer (omCRPC). Intervention consisted of SBRT. PSA reduction greater than 50% and median PFS (PSA or radiographic progression) as determined by routine care comprised outcome measurements. Cox regression analysis was used to determine factors influencing PFS.

Results

Thirty-five men with ARSI-resistant omCRPC and 65 lesions treated with SBRT were followed for a median of 17.2 months. In 63% of men PSA reduction greater than 50% was achieved. Median PFS was 9.0 months. Incomplete ablation (defined as the presence of untreated lesions after SBRT or receipt of prior palliative radiation therapy doses) was associated with worse PFS (hazard ratio 4.21 [1.74-10.19]; P < .01). For a subgroup of 22 men with complete ablation of metastatic sites with SBRT, the median PFS was 13.1 months. One-year overall survival was 93.1% (95% confidence interval, 84.4-100).

Conclusions

SBRT may augment the efficacy of ARSI in omCRPC, provided that all lesions receive ablative radiation doses. Future prospective study of SBRT for men receiving ARSI is warranted.

Metastasis-Directed Radiotherapy for Oligoprogressive or Oligopersistent Metastatic Colorectal Cancer

INTRODUCTION

Some patients with cancer may present with progressive or persistent disease at a limited number of sites following a period of treatment response. We evaluated the safety and effectiveness of metastasis-directed radiotherapy (MRT) for oligoprogressive or oligopersistent disease in patients receiving systemic treatment for metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

Patients with mCRC who received 5-fluorouracil, leucovorin, and oxaliplatin; 5-fluorouracil, leucovorin, and irinotecan; and/or capecitabine chemotherapy between 2011 and 2020 at a single institution were identified. Then, those who underwent MRT for five or fewer lesion sites while receiving systemic treatment for other metastases were categorized. The primary endpoint was time to change to systemic therapy. Secondary endpoints included MRT-related toxicity, overall survival, and local control.

RESULTS

Among 4157 patients included, 91 (2%) received MRT to limited lesion sites (55 oligoprogressive and 36 oligopersistent) during systemic treatment following a period of treatment response. The median time to change to next-line systemic therapy was 5 months in the overall cohort (measured from the current chemotherapy session) and 9.5 (range, 6.0-40.6) months in the MRT group (measured from the MRT session). No severe toxicity or systemic treatment interruption was observed following MRT. The 1-year local control and overall survival rates were 69% and 99%, respectively.

CONCLUSION

In patients with oligoprogressive or oligopersistent mCRC, MRT may be performed safely in conjunction with systemic treatment to maximize the benefit of systemic therapy and to prolong the time to change to systemic therapy. Further prospective studies should confirm these findings.

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.

Late metastatic presentation is associated with improved survival and delayed wide-spread progression after ablative stereotactic body radiotherapy for oligometastasis

Background

Stereotactic body radiotherapy (SBRT) is increasingly used to treat oligometastatic disease (OMD), but the effect of metastasis timing on patient outcomes remains uncertain.

Methods

An international database of patients with OMD treated with SBRT was assembled with rigorous quality assurance. Early versus late metastases were defined as those diagnosed ≤24 versus >24 months from the primary tumor. Overall survival (OS), progression‐free survival (PFS), and incidences of wide‐spread progression (WSP) were estimated using multivariable Cox proportional hazard models stratified by primary tumor types.

Results

The database consists of 1033 patients with median follow‐up of 24.1 months (0.3–104.7). Late metastatic presentation (N = 427) was associated with improved OS compared to early metastasis (median survival 53.6 vs. 33.0 months, hazard ratio [HR] 0.59, 95% confidence interval [CI]: 0.47–0.72, p < 0.0001). Patients with non‐small cell lung cancer (NSCLC, N = 255, HR 0.49, 95% CI: 0.33–0.74, p = 0.0005) and colorectal cancer (N = 235, HR 0.50, 95% CI: 0.30–0.84, p = 0.008) had better OS if presenting with late metastasis. Late metastasis correlated with longer PFS (median 17.1 vs. 9.0 months, HR 0.71, 95% CI: 0.61–0.83, p < 0.0001) and lower 2‐year incidence of WSP (26.1% vs. 43.6%, HR 0.60, 95% CI: 0.49–0.74, p < 0.0001). Fewer WSP were observed in patients with NSCLC (HR 0.52, 95% CI: 0.33–0.83, p = 0.006) and kidney cancer (N = 63, HR 0.37, 95% CI: 0.14–0.97, p = 0.044) with late metastases. Across cancer types, greater SBRT target size was a significant predictor for worse OS.

Conclusion

Late metastatic presentation is associated with improved survival and delayed progression in patients with OMD treated with SBRT.

[The role of radiotherapy to the primary tumor and metastases in patients with oligometastatic prostate cancer]

Oligometastatic prostate cancer is among the most studied oligometastatic cancers in the literature. However few prospective studies have assessed stereotactic body radiotherapy (SBRT) for prostate cancer oligometastases. Two randomised phase II trials show a progression-free survival benefit compared with observation. Prospective registry data show very good local control and low toxicity too. Inclusion in ongoing trials should be strongly encouraged to define the role of SBRT in addition to systemic therapy. Radiation therapy to the primary tumour has been studied in randomised trials and provides an overall survival benefit in patients with low metastatic burden. The benefit is inversely correlated with the number of bone lesions using conventional imaging, up to three metastases. Radiotherapy to the primary tumour is recommended by the learned societies for patients with low metastatic burden. Its role in combination with second generation anti androgen therapy needs to be clarified.

Nonmetastatic castration-resistant prostate cancer treated with salvage focal brachytherapy after external beam radiotherapy

INTRODUCTION

The efficacy of salvage local therapy after external beam radiotherapy has recently gained attention. However, a challenge with these therapies is the risk of significant genitourinary and gastrointestinal toxicity. Focal brachytherapy may be a treatment option because of its potential to reduce side effects.

CASE PRESENTATION

A patient with castration-resistant prostate cancer was found to be free of metastases on whole-body magnetic resonance imaging following external beam radiotherapy, and prostate biopsy revealed a localized recurrence in the ventral prostate. The patient underwent salvage focal brachytherapy and had a prostate-specific antigen progression-free survival of 23 months. No adverse effects were observed following salvage brachytherapy.

CONCLUSION

Our case suggests that salvage focal brachytherapy may be an effective local treatment option for nonmetastatic castration-resistant prostate cancer that has relapsed after external beam radiotherapy, wherein the lesion is confined to a small area within the prostate.

Local Therapies in Oligometastatic and Oligoprogressive Prostate Cancer

Oligometastatic disease was originally defined by Hellman and Weichselbaum as an intermediate-state existing between locally confined and widely disseminated malignancy, whose natural history could be positively impacted with systemic and importantly local therapies such as radiation. Currently oligometastatic prostate cancer (OPCa) is defined clinically by lesion enumeration and several subgroups exist: de novo (synchronous) oligometastatic disease present at initial diagnosis, oligorecurrent (metachronous) disease arising after definitive therapy to the prostate, and oligoprogressive disease where isolated lesions progress in a background of otherwise stable disease. In this review we highlight current knowledge and the potential future of local therapies, such as radiation to the primary prostate and metastasis-directed therapy (MDT), in the disease management of OPCa for all 3 subgroups. In addition, we examine more recent studies classifying the patterns of failure and natural history of OPCa following treatment with local therapies. Finally, while current clinical definitions of OPCa dominate, we introduce studies attempting to elucidate a more biological definition of OPCa to allow for improved selection of patients to treat with local therapies and to better inform precision combination approaches with systemic therapy.

Peripheral androgen blockade in men with castrate-sensitive biochemical recurrent prostate cancer

The aim of the study was to evaluate the feasibility of utilizing peripheral androgen blockade in men with biochemical recurrent castrate-sensitive prostate cancer. A registration study to track outcomes of men with biochemical recurrent castrate-sensitive prostate cancer treated with peripheral androgen blockade utilizing concomitant administration of finasteride and bicalutamide. Men were on intermittent peripheral blockade for a median 20.2 months, continuous peripheral blockade for a median 6.8 months, intermittent triple dose peripheral androgen blockade for a median 10.7 months, and continuous triple dose peripheral androgen blockade for 4.4 months before failing therapy. Six men (21%) had additional therapies during treatment that included metastasis-directed therapy (5/37, 14%), systemic Lu-177 (2/37, 5%), and salvage RT (1/37, 3%). The median time to progression, which includes time from initiation through all therapies to the initiation of ADT, was 37.6 months (IQR 20-74.7). From the start of PAB, median time to castrate resistance was 49.8 months (IQR 40.9-NR). After starting ADT, median time to castrate resistance was 8.8 months (IQR 4.6-17.7). Our data support the exploration of PAB as a treatment option in carefully selected patients who present with biochemical recurrence after failure of definitive local therapy for prostate cancer.

Stereotactic body radiotherapy for oligoprogressive lesions in metastatic castration-resistant prostate cancer patients during abiraterone/enzalutamide treatment

BACKGROUND

Metastasis-directed therapy (MDT) utilizing stereotactic body radiotherapy (SBRT) for oligoprogressive lesions could provide a delay in next-line systemic treatment (NEST) change while undergoing androgen receptor-targeted agents (ARTA) treatment. We evaluated prognostic factors for prostate cancer-specific survival (PCSS) and progression-free survival (PFS) to characterize patients receiving treatment with ARTA who may benefit from MDT for oligoprogressive lesions. The impact of MDT on delaying NEST and the predictive factors for NEST-free survival (NEST-FS) were also assessed.

MATERIALS AND METHODS

The clinical data of 54 metastatic castration-resistant prostate cancer patients with 126 oligoprogressive lesions receiving abiraterone (1 g/day) or enzalutamide (160 mg/day) before or after systemic chemotherapy were analyzed. A median of three lesions (range: 1-5) were treated with MDT. The primary endpoints were PCSS and PFS. The secondary endpoints were time to switch to NEST and NEST-FS.

RESULTS

The median follow-up time was 19.1 months. Univariate analysis showed that the number of oligoprogressive lesions treated with SBRT and the time between the start of ARTA treatment and oligoprogression were significant prognostic factors for PCSS, and the timing of ARTA treatment (before or after chemotherapy) and the prostate-specific antigen (PSA) response after MDT were significant prognostic factors for PFS. Multivariate analysis showed that early MDT for oligoprogressive lesions delivered less than 6 months after the beginning of ARTA and higher PSA levels after MDT were significant predictors of worse PCSS and PFS. The median total duration of ARTA treatment was 13.8 months. The median time between the start of ARTA treatment and the start of MDT for oligoprogressive lesions was 5.2 months, and MDT extended the ARTA treatment by 8.6 months on average. Thirty-two (59.3%) patients continued ARTA treatment after MDT. ARTA treatment after chemotherapy, early oligoprogression requiring MDT, and lower radiation doses for MDT were independent predictors of NEST-FS in multivariate analysis.

CONCLUSIONS

MDT for oligoprogressive lesions is effective and may provide several benefits compared to switching from ARTA treatment to NEST. Patients with early progression while on ARTAs and inadequate PSA responses after MDT have a greater risk of rapid disease progression and poor survival, which necessitates intensified treatment.