Prostate-specific Membrane Antigen: Interpretation Criteria, Standardized Reporting, and the Use of Machine Learning

Prostate-specific membrane antigen targeting positron emission tomography (PSMA-PET) is routinely used for the staging and restaging of patients with various stages of prostate cancer. For clear communication with referring physicians and to improve inter-reader agreement, the use of standardized reporting templates is mandatory. Increasingly, tumor volume is used by reporting and response assessment frameworks to prognosticate patient outcome or measure response to therapy. However, the quantification of tumor volume is often too time-consuming in routine clinical practice. Machine learning-based tools can facilitate the quantification of tumor volume for improved outcome prognostication.

Treatment Response Imaging in Prostate Cancer

Objective criteria for measuring treatment response in prostate cancer are critical to clinical research and practice. The Prostate Cancer Working Group 3 criteria are widely accepted relying only on conventional imaging for radiographic treatment response. Prostate-specific membrane antigen PET/computed tomography was proven to be superior to conventional imaging in initial diagnosis and biochemical recurrence of prostate cancer. Moreover, there is growing evidence of its role in treatment response assessment in prostate cancer. This study will review the different criteria for imaging treatment response on conventional and advanced molecular imaging for different therapies, and the future perspective in posttherapy imaging.

Clinical parameters for the prediction of occult lymph node metastasis in patients with negative PSMA-PET

BACKGROUND

Depending on the risk of LN metastasis ePLND at RP is recommended. As ePLND has potential side effects, and diagnostics have improved substantially, our objective was to evaluate the performance of the Briganti 2019 nomogram in a contemporary cohort with preoperative negative PSMA-PET.

METHODS

Patients with intermediate- and high-risk prostate cancer (CaP), undergoing RP and ePND at our center with preoperative negative [68Ga]Ga-PSMA-11 PET were included. The Accuracy of the nomogram was assessed using ROC analysis. The association of clinical parameters with the presence of LN metastasis was assessed using logistic regression. Specimen of prostate and LNs in patients with false negative PSMA-PET were additionally stained for AR and PSMA expression and assessed by IHC.

RESULTS

The study included 108 patients, 28% intermediate- and 72% high-risk. Twelve patients harbored occult LN metastasis. Accuracy of the nomogram was 0.62. [68Ga]Ga-PSMA-11 PET showed a NPV of 89%. IHC showed expression of PSMA and AR in the primary and LN metastasis in all patients. On logistic regression analysis only DRE (OR 2.72; 95%CI 1.01-7.35; P = 0.05) and percentage of cores with significant CaP (OR 1.29; 95%CI 1.05-1.60; P = 0.02) showed a significant association with LN metastasis.

CONCLUSION

The currently used nomogram is suboptimal in detecting patients with occult LNM. While the cut-off value to perform ePLND can be increased slightly following a negative PSMA-PET scan, more accurate methods of identifying these patients are needed. Whether ePLND can have a therapeutic benefit, as opposed to a diagnostic only, needs to be re-evaluated in the PSMA-PET era.

Progress in Oligometastatic Prostate Cancer: Emerging Imaging Innovations and Therapeutic Approaches

Prostate cancer (PCa) exhibits a spectrum of heterogeneity, from indolent to highly aggressive forms, with approximately 10-20% of patients experiencing metastatic PCa. Oligometastatic PCa, characterized by a limited number of metastatic lesions in specific anatomical locations, has gained attention due to advanced imaging modalities. Although patients with metastatic PCa typically receive systemic therapy, personalized treatment approaches for oligometastatic PCa are emerging, including surgical and radiotherapeutic interventions. This comprehensive review explores the latest developments in the field of oligometastatic PCa, including its biological mechanisms, advanced imaging techniques, and relevant clinical studies. Oligometastatic PCa is distinct from widespread metastases and presents challenges in patient classification. Imaging plays a crucial role in identifying and characterizing oligometastatic lesions, with new techniques such as prostate-specific membrane antigen positron emission tomography demonstrating a remarkable efficacy. The management strategies encompass cytoreductive surgery, radiotherapy targeting the primary tumor, and metastasis-directed therapy for recurrent lesions. Ongoing clinical trials are evaluating the effectiveness of these approaches. Oligometastatic PCa occupies a unique position between locally advanced and high-volume metastatic diseases. While a universally accepted definition and standardized diagnostic criteria are still evolving, emerging imaging technologies and therapeutic strategies hold promise for improving the patient outcomes in this intermediate stage of PCa.

Prostate-Specific Membrane Antigen PET/Computed Tomography: Pearls and Pitfalls

Prostate-specific membrane antigen PET (PSMA-PET) has emerged as a powerful imaging tool for prostate cancer primary staging, biochemical recurrence, and advanced disease assessment. This article offers a concise overview of the benefits and challenges associated with PSMA-PET for prostate cancer evaluation. The article highlights the advantages of PSMA-PET over conventional imaging, such as its higher sensitivity and specificity for detecting metastases, and the potential for guiding personalized treatment decisions. However, it also explores the limitations and potential pitfalls for interpretation. Overall, the article aims to provide valuable insights for clinicians and diagnostic imaging physicians in clinical practice.

The prognostic significance of a negative PSMA-PET scan prior to salvage radiotherapy following radical prostatectomy

AIM

The optimal management for early recurrent prostate cancer following radical prostatectomy (RP) in patients with negative prostate-specific membrane antigen positron-emission tomography (PSMA-PET) scan is an ongoing subject of debate. The aim of this study was to evaluate the outcome of salvage radiotherapy (SRT) in patients with biochemical recurrence with negative PSMA PET finding.

METHODS

This retrospective, multicenter (11 centers, 5 countries) analysis included patients who underwent SRT following biochemical recurrence (BR) of PC after RP without evidence of disease on PSMA-PET staging. Biochemical recurrence-free survival (bRFS), metastatic-free survival (MFS) and overall survival (OS) were assessed using Kaplan-Meier method. Multivariable Cox proportional hazards regression assessed predefined predictors of survival outcomes.

RESULTS

Three hundred patients were included, 253 (84.3%) received SRT to the prostate bed only, 46 (15.3%) additional elective pelvic nodal irradiation, respectively. Only 41 patients (13.7%) received concomitant androgen deprivation therapy (ADT). Median follow-up after SRT was 33 months (IQR: 20-46 months). Three-year bRFS, MFS, and OS following SRT were 73.9%, 87.8%, and 99.1%, respectively. Three-year bRFS was 77.5% and 48.3% for patients with PSA levels before PSMA-PET ≤ 0.5 ng/ml and > 0.5 ng/ml, respectively. Using univariate analysis, the International Society of Urological Pathology (ISUP) grade > 2 (p = 0.006), metastatic pelvic lymph nodes at surgery (p = 0.032), seminal vesicle involvement (p < 0.001), pre-SRT PSA level of > 0.5 ng/ml (p = 0.004), and lack of concomitant ADT (p = 0.023) were significantly associated with worse bRFS. On multivariate Cox proportional hazards, seminal vesicle infiltration (p = 0.007), ISUP score >2 (p = 0.048), and pre SRT PSA level > 0.5 ng/ml (p = 0.013) remained significantly associated with worse bRFS.

CONCLUSION

Favorable bRFS after SRT in patients with BR and negative PSMA-PET following RP was achieved. These data support the usage of early SRT for patients with negative PSMA-PET findings.

[Metastatic castration-resistant prostate cancer-what are rational sequential treatment options?]

BACKGROUND

In advanced prostate cancer, disease progression during ongoing androgen deprivation therapy (ADT) is referred to as castration-resistant prostate cancer (CRPC). Various therapeutic modalities are available for its treatment, including endocrine therapy, chemotherapy, poly (ADP-ribose) polymerase [PARP] inhibition, radionuclide therapy, and radioligand therapy.

OBJECTIVES

This review outlines practical aspects and considerations regarding treatment sequencing in mCRPC.

MATERIALS AND METHODS

The findings are based on existing prospective phase 3 studies that have demonstrated clinically relevant and statistically significant benefits in radiographically progression-free and/or overall survival.

RESULTS

Sequential therapy, aside from numerous patient-specific factors, depends on the treatment patients received in the hormone-sensitive prostate cancer (mHSPC) setting. Following pretreatment with ADT alone or ADT plus docetaxel in the mHSPC context, additional endocrine therapy is the standard approach. In the event of progression under combined endocrine therapy initiated in the mHSPC setting, docetaxel currently serves as the standard for the majority of patients. Patients who received triplet therapy as a pretreatment in the mHSPC scenario can be treated with radioligand therapy or second-line chemotherapy.

CONCLUSION

Various active and well-tolerated treatment options are available for patients with metastatic castration-resistant prostate cancer (mCRPC). The choice of therapy is primarily determined by previous treatments, but many other individual factors are also taken into consideration.

Prognostic Value of End-of-Treatment PSMA PET/CT in Patients Treated with 177Lu-PSMA Radioligand Therapy: A Retrospective, Single-Center Analysis

Our objective was to evaluate the prognostic value of end-of-treatment prostate-specific membrane antigen (PSMA) PET/CT (PSMA-PET) in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with 177Lu-PSMA radioligand therapy (PSMA-RLT). Methods: This was a single-center retrospective study. mCRPC patients who underwent PSMA-RLT with available baseline PSMA-PET (bPET) and end-of-treatment PSMA-PET (ePET) within 6 mo of the last PSMA-RLT cycle were eligible. Overall survival (OS) and prostate-specific antigen (PSA) progression status at the time of ePET (by Prostate Cancer Clinical Trials Working Group 3 criteria) were collected. PSMA-PET tumor segmentation was performed to obtain whole-body PSMA tumor volume (PSMA-VOL) and define progressive (≥20% increase) versus nonprogressive disease. Pairs of bPET and ePET were interpreted for appearance of new lesions. Response Evaluation Criteria in PSMA-PET/CT (RECIP) 1.0 were also applied to define progressive versus nonprogressive disease. The associations between changes in PSMA-VOL, new lesions, RECIP 1.0, and PSA progression status at the time of ePET with OS were evaluated by Kaplan-Meier analysis. Results: Twenty mCRPC patients were included. The median number of treatment cycles was 3.5 (interquartile range [IQR], 2-4). The median time between bPET and cycle 1 of PSMA-RLT was 1.0 mo (IQR, 0.7-1.8 mo). The median time between the last cycle of PSMA-RLT and ePET was 1.9 mo (IQR, 1.2-3.5 mo). Twelve of 20 patients (60%) had died at the last follow-up. The median follow-up time from ePET for survivors was 31.2 mo (IQR, 6.8-40.7 mo). The median OS from ePET was 11.4 mo (IQR, 6.8-30.7 mo). Patients with new lesions on ePET had shorter OS than those without new lesions (median OS, 10.7 mo [95% CI, 9.2-12.2] vs. not reached; P = 0.002). Patients with progressive PSMA-VOL had shorter OS than those with nonprogressive PSMA-VOL (median OS, 10.7 mo [95% CI: 9.7-11.7 mo] vs. not reached; P = 0.007). Patients with progressive RECIP had shorter OS than those with nonprogressive RECIP (median OS, 10.7 mo [95% CI, 9.7-11.7 mo] vs. not reached; P = 0.007). PSA progression at the time of ePET was associated with shorter OS (median, 10.9 mo [95% CI, 9.4-12.4 mo] vs. not reached; P = 0.028). Conclusion: In this retrospective study of 20 mCRPC patients treated with PSMA-RLT, progression on ePET by the appearance of new lesions, changes in PSMA-VOL, and RECIP 1.0 was prognostic for OS. Validation in larger, prospective multicentric clinical trials is warranted.

Deep learning based automated delineation of the intraprostatic gross tumour volume in PSMA-PET for patients with primary prostate cancer

PURPOSE

With the increased use of focal radiation dose escalation for primary prostate cancer (PCa), accurate delineation of gross tumor volume (GTV) in prostate-specific membrane antigen PET (PSMA-PET) becomes crucial. Manual approaches are time-consuming and observer dependent. The purpose of this study was to create a deep learning model for the accurate delineation of the intraprostatic GTV in PSMA-PET.

METHODS

A 3D U-Net was trained on 128 different 18F-PSMA-1007 PET images from three different institutions. Testing was done on 52 patients including one independent internal cohort (Freiburg: n = 19) and three independent external cohorts (Dresden: n = 14 18F-PSMA-1007, Boston: Massachusetts General Hospital (MGH): n = 9 18F-DCFPyL-PSMA and Dana-Farber Cancer Institute (DFCI): n = 10 68Ga-PSMA-11). Expert contours were generated in consensus using a validated technique. CNN predictions were compared to expert contours using Dice similarity coefficient (DSC). Co-registered whole-mount histology was used for the internal testing cohort to assess sensitivity/specificity.

RESULTS

Median DSCs were Freiburg: 0.82 (IQR: 0.73-0.88), Dresden: 0.71 (IQR: 0.53-0.75), MGH: 0.80 (IQR: 0.64-0.83) and DFCI: 0.80 (IQR: 0.67-0.84), respectively. Median sensitivity for CNN and expert contours were 0.88 (IQR: 0.68-0.97) and 0.85 (IQR: 0.75-0.88) (p = 0.40), respectively. GTV volumes did not differ significantly (p > 0.1 for all comparisons). Median specificity of 0.83 (IQR: 0.57-0.97) and 0.88 (IQR: 0.69-0.98) were observed for CNN and expert contours (p = 0.014), respectively. CNN prediction took 3.81 seconds on average per patient.

CONCLUSION

The CNN was trained and tested on internal and external datasets as well as histopathology reference, achieving a fast GTV segmentation for three PSMA-PET tracers with high diagnostic accuracy comparable to manual experts.

PSMA-PET detected port site recurrence of prostate cancer following minimally invasive radical prostatectomy and utilisation of hookwire localisation for excision

Biochemical recurrence following prostate cancer treatment is well-known, with predictable sites typically observed in the prostate bed, lymph nodes, or skeleton. The emergence of PSMA-PET scans has revealed the potential for early recurrence in non-conventional sites, including port site metastases. Our report presents a rare case of abdominal wall metastasis detected 97 months post-prostatectomy. The excision of this subcutaneous lesion using image-guided hookwire techniques showed promise in minimising morbidity while providing successful oncologic outcomes. Further investigation is needed to establish the efficacy of PSMA-PET-guided interventions on long-term patient outcomes in treating prostate cancer port site metastases.

Associations of quantitative whole-body PSMA-PET metrics with PSA progression status under long-term androgen deprivation therapy in prostate cancer patients: a retrospective single-center study

PURPOSE

To evaluate whether quantitative whole-body (WB) PSMA-PET metrics under long-term androgen deprivation therapy (ADT) and/or androgen receptor signaling inhibitors (ARSi) are associated with PSA progression.

METHODS

Patients who underwent at least 2 68Ga-PSMA-11 PET/CT scans between October 2016 and April 2021 (n = 372) and started a new line of ADT ± ARSi between PET1 and PET2 were retrospectively screened for inclusion. We investigated the association between PCWG3-defined PSA progression status at PET2 and the following PSMA-PET parameters: appearance of new lesions on PET2, ≥ 20% increase in WB-PSMA tumor volume (WB-PSMA-VOL), progression of disease (PD) by RECIP 1.0, and ≥ 30% increase in WB-PSMA-SUVmean from PET1 to PET2. Spearman's rank correlation coefficients and Fisher's exact test were used to evaluate the associations.

RESULTS

Thirty-five patients were included: 12/35 (34%) were treated with ADT only and 23/35 (66%) with ARSi ± ADT. The median time between PET1 and PET2 was 539 days. Changes (%) in median PSA levels, WB-PSMA-SUVmean, and WB-PSMA-VOL from PET1 to PET2 were -86%, -23%, and -86%, respectively. WB-PSMA-VOL ≥ 20%, new lesions, RECIP-PD, and WB-PSMA-SUVmean ≥ 30% were observed in 5/35 (14%), 9/35 (26%), 5/35 (14%), and 4/35 (11%) of the whole cohort, in 3/9 (33%), 7/9 (78%), 3/9 (33%), and 2/9 (22%) of patients with PSA progression at PET2, and in 2/26 (8%), 2/26 (8%), 2/26 (8%), and 2/26 (8%) of patients without PSA progression at PET2 (p = 0.058, p < 0.001, p = 0.058, p = 0.238, respectively). Changes in PSA were correlated to percent changes in WB-PSMA-VOL and WB-PSMA-SUVmean (Spearman ρ: 0.765 and 0.633, respectively; p < 0.001).

CONCLUSION

Changes in PSA correlated with changes observed on PSMA-PET, although discordance between PSA and PSMA-PET changes was observed. Further research is necessary to evaluate if PSMA-PET parameters can predict progression-free survival and overall survival and serve as novel endpoints in clinical trials.

Can PSMA PET/CT help in dose-tailoring in post-prostatectomy radiotherapy?

There are few randomized trials to evaluate the use of PSMA-PET in the planning of post-prostatectomy radiotherapy. There are two unresolved questions 1) should we increase the dose to lesions visible on PSMA-PET 2) can we reduce dose in the case of a negative PSMA-PET. In this review, we summarize and discuss the available evidence in the literature. We found that in general, there seems to be an advantage for dose-increase, but ta large recent study from the pre-PSMA era didn't show an advantage for dose escalation. Retrospective studies have shown that conventional doses to PSMA-PET-positive lesions seem sufficient. On the other hand, in the case of a negative PSMA-PET, there is no evidence that dose-reduction is possible. In the future, the combination of PSMA-PET with genomic classifiers could help in better identify patients who might benefit from either dose- de-or -increase. We further need to identify intraindividual references to help identify lesions with higher aggressiveness.

Node Oligorecurrence in Prostate Cancer: A Challenge

Within the oligometastatic state, oligorecurrent lymph node disease in prostate cancer represents an interesting clinical entity characterized by a relatively indolent biology that makes it unique: it can be treated radically, and its treatment is usually associated with a long period of control and excellent survival. Additionally, it is an emergent situation that we are facing more frequently mainly due to (a) the incorporation into clinical practice of the PSMA-PET that provides strikingly increased superior images in comparison to conventional imaging, with higher sensitivity and specificity; (b) the higher detection rates of bone and node disease with extremely low levels of PSA; and (c) the availability of high-precision technology in radiotherapy treatments with the incorporation of stereotaxic body radiotherapy (SBRT) or stereotaxic ablative radiotherapy (SABR) technology that allows the safe administration of high doses of radiation in a very limited number of fractions with low toxicity and excellent tolerance. This approach of new image-guided patient management is compelling for doctors and patients since it can potentially contribute to improving the clinical outcome. In this work, we discuss the available evidence, areas of debate, and potential future directions concerning the utilization of new imaging-guided SBRT for the treatment of nodal recurrence in prostate cancer.

PSMA-PET/CT-guided salvage radiotherapy in recurrent or persistent prostate cancer and PSA < 0.2 ng/ml

PURPOSE

The purpose of this retrospective, multicenter study was to assess efficacy of PSMA-PET/CT-guided salvage radiotherapy (sRT) in patients with recurrent or persistent PSA after primary surgery and PSA levels < 0.2 ng/ml.

METHODS

The study included patients from a pooled cohort (n = 1223) of 11 centers from 6 countries. Patients with PSA levels > 0.2 ng/ml prior to sRT or without sRT to the prostatic fossa were excluded. The primary study endpoint was biochemical recurrence-free survival (BRFS) and BR was defined as PSA nadir after sRT + 0.2 ng/ml. Cox regression analysis was performed to assess the impact of clinical parameters on BRFS. Recurrence patterns after sRT were analyzed.

RESULTS

The final cohort consisted of 273 patients; 78/273 (28.6%) and 48/273 (17.6%) patients had local or nodal recurrence on PET/CT. The most frequently applied sRT dose to the prostatic fossa was 66-70 Gy (n = 143/273, 52.4%). SRT to pelvic lymphatics was delivered in 87/273 (31.9%) patients and androgen deprivation therapy was given to 36/273 (13.2%) patients. After a median follow-up time of 31.1 months (IQR: 20-44), 60/273 (22%) patients had biochemical recurrence. The 2- and 3-year BRFS was 90.1% and 79.2%, respectively. The presence of seminal vesicle invasion in surgery (p = 0.019) and local recurrences in PET/CT (p = 0.039) had a significant impact on BR in multivariate analysis. In 16 patients, information on recurrence patterns on PSMA-PET/CT after sRT was available and one had recurrent disease inside the RT field.

CONCLUSION

This multicenter analysis suggests that implementation of PSMA-PET/CT imaging for sRT guidance might be of benefit for patients with very low PSA levels after surgery due to promising BRFS rates and a low number of relapses within the sRT field.

Metabolic response after 68Ga-PSMA-PET/CT-directed IGRT/SBRT for oligometastases prostate cancer

BACKGROUND

We used 68Ga PSMA PET/CT in the current investigation to assess the metabolic response and local control of metastasis in patients with oligometastatic prostate cancer receiving SBRT.

MATERIALS AND PROCEDURES

We performed a retrospective evaluation of the medical data of all patients with oligometastatic prostate cancer who underwent stereotactic body radiation therapy (SBRT) between 2017 and 2021. Our analysis only included medical records of patients who had SBRT for oligometastatic prostate cancer and had pre and post-SBRT 68Ga PSMA PET/CT images. Patient-related (age), disease-related (Gleason score, location of metastases), and treatment-related (factors and outcomes) data were collected from the medical files.

RESULTS

A total of 17 patients (28 lesions) with a median age of 69 years were included in the research. A median follow-up of 16.6 months was used (range 6-36 months). The median follow-up period for 68 Ga PSMA PET/CT was 8 months (the range was 5-24 months). The median pre-treatment PSA level was 1.7 ng/mL (range 0.39-18.3 ng/mL) compared to the post-treatment PSA nadir of 0.05 ng/mL (0.02-4.57). During the follow-up period, local control was 96%, and there was a link between PSMA avidity on PET. In the treated lesions, there were no recurrences. During follow-up, none of the patients experienced toxicities of grade 3 or above.

CONCLUSIONS

SBRT is a highly successful and safe way of treating patients with oligometastatic prostate cancer. Additional research is needed to examine 68Ga PSMA PET/CT to assess further for demarcation and follow-up.

(18)F-DCFPyL (PSMA) PET as a radiotherapy response assessment tool in metastatic prostate cancer

Background

Prostate Specific Membrane Antigen (PSMA) - positron emission tomography (PET) guides metastasis-directed radiotherapy (MDRT) in prostate cancer (PrCa). However, its value as a treatment response assessment tool after MDRT remains unclear. Importantly, there is limited understanding of the potential of radiotherapy (RT) to alter PSMA gene (folate hydrolase 1; FOLH1) expression.

Methodology

We reviewed a series of 11 men with oligo-metastatic PrCa (25 metastasis sites) treated with MDRT before re-staging with ¹⁸F-DCFPyL (PSMA) PET upon secondary recurrence. Acute effects of RT on PSMA protein and mRNA levels were examined with qPCR and immunoblotting in human wild-type androgen-sensitive (LNCap), castrate-resistant (22RV1) and castrate-resistant neuroendocrine (PC3 and DU145) PrCa cell lines. Xenograft tumors were analyzed with immunohistochemistry. Further, we examined PSMA expression in untreated and irradiated radio-resistant (RR) 22RV1 (22RV1-RR) and DU145 (DU145-RR) cells and xenografts selected for survival after high-dose RT.

Results

The majority of MDRT-treated lesions showed lack of PSMA-PET/CT avidity, suggesting treatment response even after low biological effective dose (BED) MDRT. We observed similar high degree of heterogeneity of PSMA expression in both human specimens and in xenograft tumors. PSMA was highly expressed in LNCap and 22RV1 cells and tumors but not in the neuroendocrine PC3 and DU145 models. Single fraction RT caused detectable reduction in PSMA protein but not in mRNA levels in LNCap cells and did not significantly alter PSMA protein or mRNA levels in tissue culture or xenografts of the other cell lines. However, radio-resistant 22RV1-RR cells and tumors demonstrated marked decrease of PSMA transcript and protein expression over their parental counterparts.

Conclusions

PSMA-PET may be a promising tool to assess RT response in oligo-metastatic PrCa. However, future systematic investigation of this concept should recognize the high degree of heterogeneity of PSMA expression within prostate tumors and the risk for loss of PSMA expression in tumor surviving curative courses of RT.

Individual radiosensitivity reflected by γ-H2AX and 53BP1 foci predicts outcome in PSMA-targeted radioligand therapy

PURPOSE

γ-H2AX and 53BP1 are fundamental for cellular DNA damage response (DDR) after radiation exposure and are linked to cell repair, arrest, or apoptosis. We aimed to evaluate whether DDR-markers in peripheral blood lymphocytes (PBLs) may have predictive potential for outcome in metastatic castration-resistant prostate cancer (mCRPC) patients receiving [177Lu]Lu-prostate-specific membrane antigen (PSMA) radioligand therapy (RLT).

METHODS

We prospectively enrolled 20 men with advanced mCRPC scheduled for PSMA-targeted RLT. Prior to the first cycle of [177Lu]Lu-PSMA RLT, all patients underwent [18F]F-PSMA-1007 positron emission tomography (PET)/computed tomography (CT) for assessment of tumor PSMA expression (assessing maximum standardized uptake value (SUVmax) of all tumor lesions). Blood samples were collected prior to, + 1 h after, and + 24 h after administration of [177Lu]Lu-PSMA, and DDR-markers γ-H2AX and 53BP1 were determined in PBLs through immunocytofluorescence. We then tested the predictive performance of DDR-markers relative to clinical and PET-based parameters for progressive disease (PSA-PD) after 2 cycles. In addition, the predictive value for progression-free survival (PSA-PFS, provided as median and 95% confidence interval [CI]) was explored.

RESULTS

Low baseline 53BP1 and γ-H2AX foci (P = 0.17) tended to predict early PSA-PD, whereas low SUVmax was significantly associated with higher risk for PSA-PD (P = 0.04). In Kaplan-Meier analysis, there was a trend towards prolonged PSA-PFS in patients with higher baseline 53BP1 of 6 months (mo; 95%CI, 4-9 mo) compared to 3 mo in patients with low 53BP1 (95% CI, 2-3 mo; P = 0.12). Comparable results were recorded for higher γ-H2AX expression (6 mo [95% CI, 3-9 mo] relative to 3 mo [95% CI, 2-4 mo] in patients with low γ-H2AX; P = 0.12). SUVmax, however, did not demonstrate predictive value (P = 0.29). Consistently, in univariate Cox-regression analysis, baseline 53BP1 foci demonstrated borderline significance for predicting PSA-PFS under [177Lu]Lu-PSMA RLT (P = 0.05).

CONCLUSION

In this prospective study investigating mCRPC patients undergoing [177Lu]Lu-PSMA RLT, low baseline DDR-markers in PBLs tended to predict poor outcome. Although the study group was small and results need further confirmation, these preliminary findings lay the foundation for exploring additive radiosensitizing or treatment intensification in future studies with high-risk individuals scheduled for RLT.

Single-fraction prostate-specific membrane antigen positron emission tomography- and multiparametric magnetic resonance imaging-guided stereotactic body radiotherapy for prostate cancer local recurrences

OBJECTIVE

To analyse the efficacy and safety of focal prostate-specific membrane antigen positron emission tomography (PSMA-PET)- and multiparametric magnetic resonance imaging (mpMRI)-guided single-fraction stereotactic body radiotherapy (SBRT) for the treatment of prostate cancer (PCa) local recurrences.

PATIENTS AND METHODS

Patients with PSMA-PET-positive PCa local recurrences treated with single-fraction SBRT between 2016 and 2020 were included. Identification for subsequent recurrences or metastatic spread based on increasing prostate-specific antigen (PSA) levels were evaluated using PSMA-PET imaging.

RESULTS

A total of 64 patients were identified. Patients received various treatments before SBRT (31 patients with radical prostatectomy [RP], 18 external beam radiotherapy [EBRT] with RP, five EBRT, and the remaining 10 other combinations). The median follow-up was 21.6 months. The median PSA level before SBRT was 1.47 ng/mL. All patients received a single-fraction treatment with a median prescription dose and isodose line of 21 Gy and 65%, respectively. At the time of SBRT, six patients (9%) received an androgen deprivation therapy (ADT). PSA levels decreased after SBRT (P = 0.03) and three local recurrences were detected during the follow-up. The progression-free survival after 1-, 2-, and 3-years was 85.3%, 65.9%, and 51.2%, respectively. Six patients (9%) started ADT after SBRT due to disease progression. The rates of newly started ADT after 1-, 2-, and 3-years were 1.8%, 7.3%, and 22.7%, respectively. Grade 1 or 2 toxicities occurred in six patients (9%); no high-grade toxicity was observed.

CONCLUSION

While the available data for SBRT in the PCa local recurrence setting describe outcomes for fractionated irradiations, the findings of this first analysis of single-fraction, PSMA-PET- and mpMRI-guided focal SBRT are encouraging. Such treatment appears to be a safe, efficient, and time-saving therapy even in intensively pretreated patients. Recurrence-directed treatments can delay the use of ADT and could avoid prostate bed irradiation in selected patients.

The Impact of PSMA-PET on Oncologic Control in Prostate Cancer Patients Who Experienced PSA Persistence or Recurrence

Background: Prostate Specific Membrane Antigen-Positron Emission Tomography (PSMA-PET) is currently recommended to restage prostate cancer (PCa) and to guide the delivery of salvage treatments. We aim to evaluate the oncologic outcomes of patients with recurrent PCa who received PSMA-PET. Methods: 324 hormone-sensitive PCa with PSA relapse after radical prostatectomy who underwent PSMA-PET in three high-volume European Centres. Patients have been stratified as pre-salvage who never received salvage treatments (n = 134), and post-salvage, including patients who received previous salvage therapies (n = 190). Patients with oligorecurrent (≤3 lesions), PSMA-positive disease underwent PSMA-directed treatments: salvage radiotherapy (sRT) or Metastases-directed therapy (MDT). Patients with polirecurrent (>3 lesions) PSMA-positive disease were treated with systemic therapy. Patients with negative PSMA-PET were treated with sRT or systemic therapies or observation. The primary outcome of the study was Progression-free survival (PFS). Secondary outcomes were: Metastases-free survival (MFS) and Castration Resistant Pca free survival (CRPC-FS). Results: median follow up was 23 months. In the pre-salvage setting, the PFS, MFS and CRPC-FS estimates at 3 years were 66.2% vs. 38.9%, 95.2% vs. 73.7% and 94.9% vs. 93.1% in patients with negative vs. positive PSMA-PET, respectively (all p ≥ 0.2). In the post-salvage setting, the PFS, MFS and CRPC-FS estimates at 3 years were 59.5% vs. 29.1%, 92.7% vs. 65.1% and 98.8% vs. 88.8% in patients with negative vs. positive PSMA-PET, respectively (all p ≤ 0.01). At multivariable analyses, a positive PSMA-PET was an independent predictor of progression (HR = 2.15) and metastatic disease (HR 2.37; all p ≤ 0.03). Conclusion: PSMA-PET in recurrent PCa detects the site of recurrence guiding salvage treatments and has a prognostic role in patients who received previous salvage treatments.

PEARLS - A multicentre phase II/III trial of extended field radiotherapy for androgen sensitive prostate cancer patients with PSMA-avid pelvic and/or para-aortic lymph nodes at presentation

PEARLS is a multi-stage randomised controlled trial for prostate cancer patients with pelvic and/or para-aortic PSMA-avid lymph node disease at presentation. The aim of the trial is to determine whether extending the radiotherapy field to cover the para-aortic lymph nodes (up to L1/L2 vertebral interspace) can improve outcomes for this patient group.

The current role of precision surgery in oligometastatic prostate cancer

Oligometastatic prostate cancer (omPCa) is a novel intermediate disease state characterized by a limited volume of metastatic cells and specific locations. Accurate staging is paramount to unmask oligometastatic disease, as provided by prostate-specific membrane antigen-positron emission tomography. Driven by the results of prospective trials employing conventional and/or modern staging modalities, the treatment landscape of omPCa has rapidly evolved over the last years. Several treatment-related questions comprising the concept of precision strikes are under development. For example, beyond systemic therapy, cohort studies have found that cytoreductive radical prostatectomy (CRP) can confer a survival benefit in select patients with omPCa. More importantly, CRP has been consistently shown to improve long-term local symptoms when the tumor progresses across disease states due to resistance to systemic therapies. Metastasis-directed treatments have also emerged as a promising treatment option due to the visibility of oligometastatic disease and new technologies as well as treatment strategies to target the novel PCa colonies. Whether metastases are present at primary cancer diagnosis or detected upon biochemical recurrence after treatment with curative intent, targeted yet decisive elimination of disseminated tumor cell hotspots is thought to improve survival outcomes. One such strategy is salvage lymph node dissection in oligorecurrent PCa which can alter the natural history of progressive PCa. In this review, we will highlight how refinements in modern staging modalities change the classification and treatment of (oligo-)metastatic PCa. Further, we will also discuss the current role and future directions of precision surgery in omPCa.

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

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

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.

The maximum standardized uptake value in patients with recurrent or persistent prostate cancer after radical prostatectomy and PSMA-PET-guided salvage radiotherapy-a multicenter retrospective analysis

Purpose

This study aims to evaluate the association of the maximum standardized uptake value (SUVmax) in positron-emission tomography targeting prostate-specific membrane antigen (PSMA-PET) prior to salvage radiotherapy (sRT) on biochemical recurrence free survival (BRFS) in a large multicenter cohort.

Methods

Patients who underwent ⁶⁸ Ga-PSMA11-PET prior to sRT were enrolled in four high-volume centers in this retrospective multicenter study. Only patients with PET-positive local recurrence (LR) and/or nodal recurrence (NR) within the pelvis were included. Patients were treated with intensity-modulated-sRT to the prostatic fossa and elective lymphatics in case of nodal disease. Dose escalation was delivered to PET-positive LR and NR. Androgen deprivation therapy was administered at the discretion of the treating physician. LR and NR were manually delineated and SUVmax was extracted for LR and NR. Cox-regression was performed to analyze the impact of clinical parameters and the SUVmax-derived values on BRFS.

Results

Two hundred thirty-five patients with a median follow-up (FU) of 24 months were included in the final cohort. Two-year and 4-year BRFS for all patients were 68% and 56%. The presence of LR was associated with favorable BRFS (p = 0.016). Presence of NR was associated with unfavorable BRFS (p = 0.007). While there was a trend for SUVmax values ≥ median (p = 0.071), SUVmax values ≥ 75% quartile in LR were significantly associated with unfavorable BRFS (p = 0.022, HR: 2.1, 95%CI 1.1–4.6). SUVmax value in NR was not significantly associated with BRFS. SUVmax in LR stayed significant in multivariate analysis (p = 0.030). Sensitivity analysis with patients for who had a FU of > 12 months (n = 197) confirmed these results.

Conclusion

The non-invasive biomarker SUVmax can prognosticate outcome in patients undergoing sRT and recurrence confined to the prostatic fossa in PSMA-PET. Its addition might contribute to improve risk stratification of patients with recurrent PCa and to guide personalized treatment decisions in terms of treatment intensification or de-intensification.

This article is part of the Topical Collection on Oncology—Genitourinary.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-022-05931-5.

PSMA-guided metastases directed therapy for bone castration sensitive oligometastatic prostate cancer: a multi-institutional study

To assess the outcomes of a cohort of bone oligometastatic prostate cancer patients treated with PSMA-PET guided stereotactic body radiotherapy (SBRT). From April 2017 to January 2021, 40 patients with oligorecurrent prostate cancer detected by PSMA-PET were treated with SBRT for bone oligometastases. Concurrent androgen deprivation therapy was an exclusion criterion. A total of 56 prostate cancer bone oligometastases were included in the present analysis. In 28 patients (70%), oligometastatic disease presented as a single lesion, two lesions in 22.5%, three lesions in 5%, four lesions in 2.5%. 30.3% were spine-metastases, while 69.7% were non-spine metastases. SBRT was delivered for a median dose of 30 Gy (24-40 Gy) in 3-5 fractions, with a median EQD₂ = 85 Gy₂ (64.3-138.9Gy₂). With a median follow-up of 22 months (range 2-48 months), local control (LC) 1- and 2-years rates were 96.3% and 93.9%, while distant progression-free survival (DPFS) rates were 45.3% and 27%. At multivariate analysis, the lower PSA nadir value after SBRT remained significantly related to better DPFS rates (p = 0.03). In 7 patients, a second SBRT course was proposed with concurrent ADT, while 11 patients, due to polymetastatic spread, received ADT alone, resulting in 1- and 2-years ADT-free survival rates of 67.5% and 61.8%. At multivariate analysis, a lower number of treated oligometastases maintained a correlation with higher ADT-free survival rates (p = 0.04). In our experience, PSMA-PET guided SBRT resulted in excellent results in terms of clinical outcomes, representing a helpful tool with the aim to delay the start of ADT.

Pilot study of the diagnostic utility of 89 Zr-df-IAB2M and 68 Ga-PSMA-11 PET imaging and multiparametric MRI in localized prostate cancer

BACKGROUND

Accurate diagnosis of localized prostate cancer (PCa) is limited by inadequacy of multiparametric (mp) MRI to fully identify and differentiate localized malignant tissue from benign pathologies. Prostate-specific membrane antigen (PSMA) represents an excellent target for molecular imaging. IAB2M, an 85-kD minibody derived from a de-immunized monoclonal antibody directed at the extracellular domain of human PSMA (huJ591), and PSMA-11, a small molecule ligand have been previously tested as probes for visualization of recurrent/metastatic PCa with PET/CT. This pilot, non-randomized trial studied their diagnostic utility in patients (pts) with localized PCa.

METHODS

Pts planned for radical prostatectomy (RP) were enrolled and underwent mpMRI and PET/CT imaging with ⁸⁹ Zr-df-IAB2M and/or ⁶⁸ Ga-PSMA-PET/CT. Image results were read by a radiologist blinded to clinical information and pathology results, mapped and compared to corresponding histopathology findings from all lesions, both clinically significant and nonsignificant. The detection rates of all three imaging modalities were measured and correlated.

RESULTS

20 pts with median age of 64.5 (46-79) years and PSA level of 7.5 (1.6-36.56) ng/ml were enrolled. 19 pts underwent RP and were imaged pre-operatively with ⁸⁹ Zr-Df-IAB2M PET/CT and mpMRI. Nine of those were imaged using ⁶⁸ Ga-PSMA-11 as well. Out of 48 intraprostatic lesions verified on surgical pathology, IAB2M PET/CT was able to detect 36 (75%). A similar proportion of pathologically confirmed, clinically significant lesions (22/29, 76%) was detected. IAB2M PET/CT was also able to identify 14/19 (74%) extraprostatic lesions. The performance of mpMRI was inferior, with 24/48 detectable lesions (50%) and 18/29 clinically significant intraprostatic lesions (62%). Compared to the current standard (mpMRI), IAB2M PET/CT had a sensitivity of 88%, specificity 38%, positive predictive value 58%, and accuracy 63%. In 9 pts who underwent Ga-PSMA-11 as well, the latter yielded a detection rate of 70% (14/20), which was also seen in clinically significant lesions (10/14, 71%). Ga-PSMA-11 PET/CT also detected 4/6 (67%) extraprostatic lesions.

CONCLUSIONS

In this pilot study, the performance of ⁸⁹ Zr-df-IAB2M was superior to mpMRI and similar to ⁶⁸ Ga-PSMA-11 PET/CT. The higher detection rate of PSMA-PET supports its use as a diagnostic tool with consequent management change implications in men with localized PCa.

PSMA-PET/MRI-Based Focal Dose Escalation in Patients with Primary Prostate Cancer Treated with Stereotactic Body Radiation Therapy (HypoFocal-SBRT): Study Protocol of a Randomized, Multicentric Phase III Trial

Technical advances in radiotherapy (RT) treatment planning and delivery have substantially changed RT concepts for primary prostate cancer (PCa) by (i) enabling a reduction of treatment time, and by (ii) enabling safe delivery of high RT doses. Several studies proposed a dose-response relationship for patients with primary PCa and especially in patients with high-risk features, as dose escalation leads to improved tumor control. In parallel to the improvements in RT techniques, diagnostic imaging techniques like multiparametric magnetic resonance imaging (mpMRI) and positron-emission tomography targeting prostate-specific-membrane antigen (PSMA-PET) evolved and enable an accurate depiction of the intraprostatic tumor mass for the first time. The HypoFocal-SBRT study combines ultra-hypofractionated RT/stereotactic body RT, with focal RT dose escalation on intraprostatic tumor sides by applying state of the art diagnostic imaging and most modern RT concepts. This novel strategy will be compared with moderate hypofractionated RT (MHRT), one option for the curative primary treatment of PCa, which has been proven by several prospective trials and is recommended and carried out worldwide. We suspect an increase in relapse-free survival (RFS), and we will assess quality of life in order to detect potential changes.

Prostate adenocarcinoma with mucinous features - is it PSMA avid?

Mucinous prostate adenocarcinoma represents <0.1% of prostate cancers. To our knowledge, no previous report has described the ⁶⁸ Ga-PSMA-PET characteristics of this entity at the primary site. We present a case of a fit 85-year-old with PSA 0.55 ng/mL and ISUP grade 4 acinar adenocarcinoma with mucinous features on biopsy. ⁶⁸ Ga-PSMA-PET revealed an intensely avid primary lesion in the right prostate (SUVmax 10.9), concordant with biopsy findings and encompassing both the PI-RADS 5 lesion identified on MRI and a PI-RADS 1 lesion that presumably represented the mucinous component. The patient was treated with definitive radiotherapy to the prostate and lymph nodes with 6 months of androgen deprivation therapy.

A survey among German-speaking radiation oncologists on PET-based radiotherapy of prostate cancer

Background

Positron emission tomography-(PET) has evolved as a powerful tool to guide treatment for prostate cancer (PC). The aim of this survey was to evaluate the acceptance and use of PET—especially with prostate-specific membrane antigen (PSMA) targeting tracers—in clinical routine for radiotherapy (RT) and the impact on target volume definition and dose prescription.

Methods

We developed an online survey, which we distributed via e-mail to members of the German Society of Radiation Oncology (DEGRO). The survey included questions on patterns of care of RT for PC with/without PET. For evaluation of doses we used the equivalent dose at fractionation of 2 Gy with α/β = 1.5 Gy [EQD2(1.5 Gy)].

Results

From 109 participants, 78.9% have the possibility to use PET for RT planning. Most centers use PSMA-targeting tracers (98.8%). In 39.5%, PSMA-PET for biochemical relapse after prior surgery is initiated at PSA ≥ 0.5 ng/mL, while 30.2% will perform PET at ≥ 0.2 ng/mL (≥ 1.0 ng/mL: 16.3%, ≥ 2.0 ng/mL: 2.3%, regardless of PSA: 11.7%). In case of PET-positive local recurrence (LR) and pelvic lymph nodes (LNs), 97.7% and 96.5% of the participants will apply an escalated dose. The median total dose in EQD2(1.5 Gy) was 70.00 Gy (range: 56.89–85.71) for LR and 62.00 Gy (range: 52.61–80.00) for LNs. A total number of ≤ 3 (22.0%) or ≤ 5 (20.2%) distant lesions was most often described as applicable for the definition as oligometastatic PC.

Conclusion

PSMA-PET is widely used among German radiation oncologists. However, specific implications on treatment planning differ among physicians. Therefore, further trials and guidelines for PET-based RT are warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-021-01811-8.

Diagnostic efficiency of hybrid imaging using PSMA ligands, PET/CT, PET/MRI and MRI in identifying malignant prostate lesions

OBJECTIVE

The objective of this study was to assess the accuracy of 68Ga-PSMA-11 PET/MRI, 18F-PSMA-1007 PET/CT, 68Ga-PSMA-11 PET/CT, and multiparametric (mp)MRI for the delineating of dominant intraprostatic lesions (IPL).

MATERIALS AND METHODS

35 patients with organ-confined prostate cancer who were assigned to definitive radiotherapy (RT) were divided into three groups based on imaging techniques: 68Ga-PSMA-PET/MRI (n = 9), 18F-PSMA-PET/CT (n = 16) and 68Ga-PSMA-PET/CT (n = 10). All patients without PSMA-PET/MRI received an additional mpMRI. PSMA-PET-based automatic isocontours and manual contours of the dominant IPLs were generated for each modality. The biopsy results were then used to validate whether any of the prostate biopsies were positive in the marked lesion using Dice similarity coefficient (DSC), Youden index (YI), sensitivity and specificity. Factors that can predict the accuracy of IPLs contouring were analysed.

RESULTS

Diagnostic performance was significantly superior both for manual and automatic IPLs contouring using 68Ga-PSMA-PET/MRI (DSC/YI SUV70%-0.62/0.51), 18F-PSMA-PET/CT (DSC/YI SUV70%-0.67/0.53) or 68Ga-PSMA-PET/CT (DSC/YI SUV70%-0.63/0.51) compared to mpMRI (DSC/YI-0.47/0.41; p < 0.001). The accuracy for delineating IPLs was not improved by combination of PET/CT and mpMRI images compared to PET/CT alone. Significantly superior diagnostic accuracy was found for large prostate lesions (at least 15% from the prostate volume) and higher Gleason score (at least 7b) comparing to smaller lesions with lower GS.

CONCLUSION

IPL localization was significantly improved when using PSMA-imaging procedures compared to mpMRI. No significant difference for delineating IPLs was found between hybrid method PSMA-PET/MRI and PSMA-PET/CT. PSMA-based imaging technique should be considered for the diagnostics of IPLs and focal treatment modality.

E-PSMA: the EANM standardized reporting guidelines v1.0 for PSMA-PET

RATIONALE

The development of consensus guidelines for interpretation of Prostate-Specific Membrane Antigen (PSMA)-Positron Emission Tomography (PET) is needed to provide more consistent reports in clinical practice. The standardization of PSMA-PET interpretation may also contribute to increasing the data reproducibility within clinical trials. Finally, guidelines in PSMA-PET interpretation are needed to communicate the exact location of findings to referring physicians, to support clinician therapeutic management decisions.

METHODS

A panel of worldwide experts in PSMA-PET was established. Panelists were selected based on their expertise and publication record in the diagnosis or treatment of PCa, in their involvement in clinical guidelines and according to their expertise in the clinical application of radiolabeled PSMA inhibitors. Panelists were actively involved in all stages of a modified, nonanonymous, Delphi consensus process.

RESULTS

According to the findings obtained by modified Delphi consensus process, panelist recommendations were implemented in a structured report for PSMA-PET.

CONCLUSIONS

The E-PSMA standardized reporting guidelines, a document supported by the European Association of Nuclear Medicine (EANM), provide consensus statements among a panel of experts in PSMA-PET imaging, to develop a structured report for PSMA-PET in prostate cancer and to harmonize diagnostic interpretation criteria.

Prior PSMA PET-CT Imaging and Hounsfield Unit Impact on Tumor Yield and Success of Molecular Analyses from Bone Biopsies in Metastatic Prostate Cancer

Simple Summary

Prostate cancer is currently the fifth leading cause of death in men worldwide. To personalize and guide treatment in prostate cancer, identification of druggable genomic alterations is of major importance. Prostate cancer often metastasizes solely or predominantly to the bones, with molecular analyses on bone biopsies challenging due to technical difficulties to identify and obtain biopsies from high tumor cell containing locations. In our retrospective analysis, we showed a significantly higher success rate in patients where biopsy location was selected by a prior PSMA PET-CT compared to solely CT or MRI. CT-guided biopsies in locations with low Hounsfield units (HUs) and deviation of HUs were associated with a higher proportion of successful histological and molecular biopsies. Based on these results, we designed a simple prediction model for daily clinical practice to increase the success rate of bone biopsies for molecular analyses in prostate cancer to guide precision medicine.

Abstract

Developing and optimizing targeted therapies in metastatic castration-resistant prostate cancer (mCRPC) necessitates molecular characterization. Obtaining sufficient tumor material for molecular characterization has been challenging. We aimed to identify clinical and imaging variables of imaging-guided bone biopsies in metastatic prostate cancer patients that associate with tumor yield and success in obtaining molecular results, and to design a predictive model: Clinical and imaging data were collected retrospectively from patients with prostate cancer who underwent a bone biopsy for histological and molecular characterization. Clinical characteristics, imaging modalities and imaging variables, were associated with successful biopsy results. In our study, we included a total of 110 bone biopsies. Histological conformation was possible in 84 of all biopsies, of which, in 73 of the 84, successful molecular characterization was performed. Prior use of PSMA PET-CT resulted in higher success rates in histological and molecular successful biopsies compared to CT or MRI. Evaluation of spine biopsies showed more often successful results compared to other locations for both histological and molecular biopsies (p = 0.027 and p = 0.012, respectively). Low Hounsfield units (HUs) and deviation (Dev), taken at CT-guidance, were associated with histological successful biopsies (p = 0.025 and p = 0.023, respectively) and with molecular successful biopsies (p = 0.010 and p = 0.006, respectively). A prediction tool combining low HUs and low Dev resulted in significantly more successful biopsies, histological and molecular (p = 0.023 and p = 0.007, respectively). Based on these results, we concluded that site selection for metastatic tissue biopsies with prior PSMA PET-CT imaging improves the chance of a successful biopsy. Further optimization can be achieved at CT-guidance, by selection of low HU and low Dev lesions. A prediction tool is provided to increase the success rate of bone biopsies in mCRPC patients, which can easily be implemented in daily practice.

Uncovering the invisible-prevalence, characteristics, and radiomics feature-based detection of visually undetectable intraprostatic tumor lesions in 68GaPSMA-11 PET images of patients with primary prostate cancer

Introduction

Primary prostate cancer (PCa) can be visualized on prostate-specific membrane antigen positron emission tomography (PSMA-PET) with high accuracy. However, intraprostatic lesions may be missed by visual PSMA-PET interpretation. In this work, we quantified and characterized the intraprostatic lesions which have been missed by visual PSMA-PET image interpretation. In addition, we investigated whether PSMA-PET-derived radiomics features (RFs) could detect these lesions.

Methodology

This study consists of two cohorts of primary PCa patients: a prospective training cohort (n = 20) and an external validation cohort (n = 52). All patients underwent ⁶⁸Ga-PSMA-11 PET/CT and histology sections were obtained after surgery. PCa lesions missed by visual PET image interpretation were counted and their International Society of Urological Pathology score (ISUP) was obtained. Finally, 154 RFs were derived from the PET images and the discriminative power to differentiate between prostates with or without visually undetectable lesions was assessed and areas under the receiver-operating curve (ROC-AUC) as well as sensitivities/specificities were calculated.

Results

In the training cohort, visual PET image interpretation missed 134 tumor lesions in 60% (12/20) of the patients, and of these patients, 75% had clinically significant (ISUP > 1) PCa. The median diameter of the missed lesions was 2.2 mm (range: 1–6). Standard clinical parameters like the NCCN risk group were equally distributed between patients with and without visually missed lesions (p < 0.05). Two RFs (local binary pattern (LBP) size-zone non-uniformality normalized and LBP small-area emphasis) were found to perform excellently in visually unknown PCa detection (Mann-Whitney U: p < 0.01, ROC-AUC: ≥ 0.93). In the validation cohort, PCa was missed in 50% (26/52) of the patients and 77% of these patients possessed clinically significant PCa. The sensitivities of both RFs in the validation cohort were ≥ 0.8.

Conclusion

Visual PSMA-PET image interpretation may miss small but clinically significant PCa in a relevant number of patients and RFs can be implemented to uncover them. This could be used for guiding personalized treatments.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-020-05111-3.

Thyroid and androgen receptor signaling are antagonized by μ-Crystallin in prostate cancer

Androgen deprivation therapy (ADT) remains a key approach in the treatment of prostate cancer (PCa). However, PCa inevitably relapses and becomes ADT resistant. Besides androgens, there is evidence that thyroid hormone thyroxine (T4) and its active form 3,5,3'-triiodo-L-thyronine (T3) are involved in the progression of PCa. Epidemiologic evidences show a higher incidence of PCa in men with elevated thyroid hormone levels. The thyroid hormone binding protein μ-Crystallin (CRYM) mediates intracellular thyroid hormone action by sequestering T3 and blocks its binding to cognate receptors (TRα/TRβ) in target tissues. We show in our study that low CRYM expression levels in PCa patients are associated with early biochemical recurrence and poor prognosis. Moreover, we found a disease stage-specific expression of CRYM in PCa. CRYM counteracted thyroid and androgen signaling and blocked intracellular choline uptake. CRYM inversely correlated with [18F]fluoromethylcholine (FMC) levels in positron emission tomography/magnetic resonance imaging of PCa patients. Our data suggest CRYM as a novel antagonist of T3- and androgen-mediated signaling in PCa. The role of CRYM could therefore be an essential control mechanism for the prevention of aggressive PCa growth.

Intraprostatic Tumor Segmentation on PSMA PET Images in Patients with Primary Prostate Cancer with a Convolutional Neural Network

Accurate delineation of the intraprostatic gross tumor volume (GTV) is a prerequisite for treatment approaches in patients with primary prostate cancer (PCa). Prostate-specific membrane antigen PET (PSMA PET) may outperform MRI in GTV detection. However, visual GTV delineation underlies interobserver heterogeneity and is time consuming. The aim of this study was to develop a convolutional neural network (CNN) for automated segmentation of intraprostatic tumor (GTV-CNN) in PSMA PET. Methods: The CNN (3D U-Net) was trained on the ⁶⁸Ga-PSMA PET images of 152 patients from 2 different institutions, and the training labels were generated manually using a validated technique. The CNN was tested on 2 independent internal (cohort 1: ⁶⁸Ga-PSMA PET, n = 18 and cohort 2: ¹⁸F-PSMA PET, n = 19) and 1 external (cohort 3: ⁶⁸Ga-PSMA PET, n = 20) test datasets. Accordance between manual contours and GTV-CNN was assessed with the Dice-Sørensen coefficient (DSC). Sensitivity and specificity were calculated for the 2 internal test datasets (cohort 1: n = 18, cohort 2: n = 11) using whole-mount histology. Results: The median DSCs for cohorts 1-3 were 0.84 (range: 0.32-0.95), 0.81 (range: 0.28-0.93), and 0.83 (range: 0.32-0.93), respectively. Sensitivities and specificities for the GTV-CNN were comparable with manual expert contours: 0.98 and 0.76 (cohort 1) and 1 and 0.57 (cohort 2), respectively. Computation time was around 6 s for a standard dataset. Conclusion: The application of a CNN for automated contouring of intraprostatic GTV in ⁶⁸Ga-PSMA and ¹⁸F-PSMA PET images resulted in a high concordance with expert contours and in high sensitivities and specificities in comparison with histology as a reference. This robust, accurate and fast technique may be implemented for treatment concepts in primary prostate cancer. The trained model and the study's source code are available in an open source repository.

Imaging for Metastasis in Prostate Cancer: A Review of the Literature

Background: Initial staging and assessment of treatment activity in metastatic prostate cancer (PCa) patients is controversial. Indications for the various available imaging modalities are not well-established due to rapid advancements in imaging and treatment.

Methods: We conducted a critical literature review of the main imaging abnormalities that suggest a diagnosis of metastasis in localized and locally advanced PCa or in cases of biological relapse. We also assessed the role of the various imaging modalities available in routine clinical practice for the detection of metastases and response to treatment in metastatic PCa patients.

Results: In published clinical trials, the most commonly used imaging modalities for the detection and evaluation of therapeutic response are bone scan, abdominopelvic computed tomography (CT), and pelvic and bone magnetic resonance imaging (MRI). For the detection and follow-up of metastases during treatment, modern imaging techniques i.e., choline-positron emission tomography (PET), fluciclovine-PET, or Prostate-specific membrane antigen (PSMA)-PET provide better sensitivity and specificity. This is particularly the case of fluciclovine-PET and PSMA-PET in cases of biochemical recurrence with low values of prostate specific antigen.

Conclusions: In routine clinical practice, conventional imaging still have a role, and communication between imagers and clinicians should be encouraged. Present and future clinical trials should use modern imaging methods to clarify their usage.

Treatment of non-metastatic castration resistant prostate cancer in 2020: What is the best?

Lately the development of 3 novel second-generation androgen receptor antagonists (enzalutamide, apalutamide, and darolutamide) chanced the treatment landscape of nonmetastatic castration-resistant prostate cancer. After proofing their clinical efficacy in large phase III registration trials with good compatibilities and tolerable side effects currently all 3 substances are Food and Drug Administration-approved in nonmetastatic castration-resistant prostate cancer. The present short review article provides an overview about these new treatment options and discusses their use in daily routine focusing on patient selection as well as on the impact of novel sensitive imaging modalities like prostate-specific membrane antigen-positron-emission tomography for detection of this stage of disease.

[68Ga-]PSMA-11 PET/CT and multiparametric MRI for gross tumor volume delineation in a slice by slice analysis with whole mount histopathology as a reference standard - Implications for focal radiotherapy planning in primary prostate cancer

BACKGROUND AND PURPOSE

Focal therapies are a promising approach to treat prostate cancer (PCa) more precisely instead of conventional whole gland treatment. Nowadays, multiparametric MRI (mpMRI) is routinely used for gross tumor volume (GTV) delineation. The aim of our study was to compare PSMA-PET/CT and mpMRI for the delineation of intraprostatic tumor burden by using whole mount histopathology as a reference standard.

MATERIAL AND METHODS

17 prospectively enrolled patients with primary PCa underwent [⁶⁸Ga-]PSMA-11 PET/CT and mpMRI before radical prostatectomy. PSMA-PET/CT, mpMRI and histopathology of the resected specimens were co-registered. Two teams of experts generated GTV contours for mpMRI and PET, respectively. The imaging was validated on a lesion level and slice by slice in quadrants based on the distribution of PCa in histopathology. Overall, 772 quadrants were analyzed with 414 being true positive for tumor (53.6%).

RESULTS

Median tumor volumes were 10.4 ml for GTV-histo, 10.8 ml for PSMA-PET and 4.5 ml for mpMRI. Median tumor volume in mpMRI was significant (p < 0.05) smaller than GTV-PET and GTV-histo, respectively. The sensitivity and specificity were 86% and 87% for PSMA-PET, 58% and 94% for mpMRI and 91% and 84% for their GTV-union. In 133 quadrants PSMA-PET/CT correctly identified tumor where mpMRI found none. MpMRI identified 19 true positive quadrants exclusively.

CONCLUSION

Our investigation demonstrates an increased consensus of PSMA-PET with histopathology compared to mpMRI for intraprostatic GTV delineation, especially with a higher sensitivity. Additionally mpMRI contours underestimate tumor volume significantly. Thus PSMA-PET may be a complementary augmentation for GTV delineation in focal therapies.

Metastases-yield and Prostate-specific Antigen Kinetics Following Salvage Lymph Node Dissection for Prostate Cancer: A Comparison Between Conventional Surgical Approach and Prostate-specific Membrane Antigen-radioguided Surgery

The first results on ^99mTechnetium prostate-specific membrane antigen-radioguided surgery (^99mTc-PSMA- RGS) showed promising outcome. Here, we sought to evaluate if this targeted molecular surgical approach might be more effective than conventional salvage lymph node dissection (sLND). We prospectively analysed 42 consecutive patients who underwent sLND based on preoperative ⁶⁸Gallium (⁶⁸Ga)-PSMA-positron emission tomography (PET) imaging between 2015 and 2018. In 29 patients, the dissection field was based solely ⁶⁸Ga-PSMA-PET imaging (conventional surgical approach [CSA]), whereas 13 patients underwent ^99mTc-PSMA-RGS. Preoperative characteristics of both groups were similar. Final pathology revealed no metastases in nine CSA patients (31%), whereas all visible lesions on preoperative ⁶⁸Ga-PSMA-PET were removed in patients who underwent RGS. A PSA decline in general, >50% and >90% within 6 wk was seen in 50%, 29%, and 7% versus 100%, 92%, and 53% in CSA versus RGS groups, respectively (all p<0.01). This is the first comparison of conventional and PSMA-radioguided approach with regards to short-term efficacy of sLND. Although long-term outcome needs to be awaited, RGS offers promising results. PATIENT SUMMARY: We compared two surgical approaches for lymph node dissection in lymph node only recurrent prostate cancer patients. The radioguided approach was superior in removing the affected lymph nodes, resulting in a more pronounced prostate-specific antigen decline.

Importance of 68Ga-PSMA PET/CT in hospital practice. View of the radiation oncologist

Radiotherapy is a treatment with curative intent, both in patients with primary diagnosis of prostate cancer (PCa) and in patients presenting with biochemical recurrence after radical prostatectomy (RP). Moreover, the use of stereotactic body radiotherapy as a metastasis directed therapy in patients with oligometastatic PCa has significantly increased in the recent years. Conventional imaging techniques, including transrectal ultrasound, computed tomography (CT), morphologic magnetic resonance and bone scintigraphy have traditionally played a minor role in all those clinical scenarios due to its low diagnostic accuracy. The recent development of the positron emission tomography (PET) radiotracer ⁶⁸Ga-PSMA binding to the prostate specific membrane antigen (PSMA), a transmembrane glycoprotein overexpressed in PCa cells, has shown promising results. Detection rates for PCa lesions are higher than CT and higher than the best technique available, the PET/CT with choline. Its superiority has been demonstrated even at very low PSA levels (<1 ng/ml). This increase in diagnostic accuracy represents a potential impact on patient management, especially in radiotherapy. Even if this imaging technique is already available for routine clinical practice in some European countries, in Spain, unfortunately, there is very limited access. In this review, we analyze the main studies that investigate the usefulness of ⁶⁸Ga-PSMA PET/CT in patients with PCa and its potential impact on radiotherapy treatments. In addition, we compared the ⁶⁸Ga-PSMA PET/CT, with the multiparametric magnetic resonance imaging and the PET/CT with choline, in the different clinical scenarios.

[Imaging in individualized uro-oncology]

The recent introduction of new diagnostic techniques has revolutionized uro-oncolgy. In addition to multiparametric magnetic resonance imaging (mpMRI), prostate-specific membrane antigen positron-emission tomography (PSMA-PET) plays an increasingly import role in daily practice. The introduction of three-dimensional (3D) printing technologies in the context of robot-assisted uro-oncological surgery represents a first step towards individualized 3D imaging. In the era of immunotherapy, imaging is challenged by new diagnostic criteria (iRECIST) and immune-related adverse effects.

Radiotherapy for recurrent prostate cancer: 2018 Recommendations of the Australian and New Zealand Radiation Oncology Genito-Urinary group

The management of patients with biochemical, local, nodal, or oligometastatic relapsed prostate cancer has become more challenging and controversial. Novel imaging modalities designed to detect recurrence are increasingly used, particularly PSMA-PET scans in Australia, New Zealand and some European countries. Imaging techniques such as MRI and PET scans using other prostate cancer-specific tracers are also being utilised across the world. The optimal timing for commencing salvage treatment, and the role of local and/or systemic therapies remains controversial. Through surveys of the membership, the Australian and New Zealand Faculty of Radiation Oncology Genito-Urinary Group (FROGG) identified wide variation in the management of recurrent prostate cancer. Following a workshop conducted in April 2017, the FROGG management committee reviewed the literature and developed a set of recommendations based on available evidence and expert opinion, for the appropriate investigation and management of recurrent prostate cancer. These recommendations cover the role and timing of post-prostatectomy radiotherapy, the management of regional nodal metastases and oligometastases, as well as the management of local prostate recurrence after definitive radiotherapy.

PSMA-PET based radiotherapy: a review of initial experiences, survey on current practice and future perspectives

⁶⁸Gallium prostate specific membrane antigen (PSMA) ligand positron emission tomography (PET) is an increasingly used imaging modality in prostate cancer, especially in cases of tumor recurrence after curative intended therapy. Owed to the novelty of the PSMA-targeting tracers, clinical evidence on the value of PSMA-PET is moderate but rapidly increasing. State of the art imaging is pivotal for radiotherapy treatment planning as it may affect dose prescription, target delineation and use of concomitant therapy.

This review summarizes the evidence on PSMA-PET imaging from a radiation oncologist’s point of view. Additionally a short survey containing twelve examples of patients and 6 additional questions was performed in seven mayor academic centers with experience in PSMA ligand imaging and the findings are reported here.

Biochemical Recurrence of Prostate Cancer: Initial Results with [18F]PSMA-1007 PET/CT

Biochemical recurrence (BCR) is a concern for prostate cancer patients after local treatment. ⁶⁸Ga-labeled prostate-specific membrane antigen (PSMA) ligands have significantly improved prostate cancer imaging. However, several ¹⁸F-labeled ligands that were developed as fluorinated tracers might present advantages. In this study, we analyzed the potential of ¹⁸F-PSMA-1007 in patients with BCR. Methods: Twelve patients with BCR after local treatment underwent PET/CT scans 1 and 3 h after injection of ¹⁸F-PSMA-1007. Results:¹⁸F-PSMA-1007 PET/CT detected lesions in 9 of 12 patients (75%). A significant difference was observed when comparing the tracer uptake in ¹⁸F-PSMA-1007-positive lesions 1 and 3 h after injection (median SUV_max, 7.00 vs. 11.34; P < 0.001; n = 76). Forty-four (88%) of 50 ¹⁸F-PSMA-1007-positive lymph nodes had a short-axis diameter of less than 8 mm. Conclusion: In this pilot study, ¹⁸F-PSMA-1007 PET/CT presented high potential for localization of recurrent disease in prostate cancer patients with BCR.

The Role of Local Therapy for Oligometastatic Prostate Cancer: Should We Expect a Cure?

The role of local treatment in oligometastatic prostate cancer remains contentious. Treatment of the prostate in metastatic disease may confer benefit, but prospective data are lacking. With improvements in treatments, aggressive strategies directed at metastases have increasingly become of clinical interest. Current evidence suggests good local control can be achieved; however, further data are required to determine overall cancer outcomes. This article evaluates the evidence available and consider whether local treatment of oligometastatic disease is a feasible, safe, and a positive strategy in this disease cohort. Cure should not be expected, although prolonged disease and treatment-free survival may be observed.

Simultaneous whole-body 18F-PSMA-1007-PET/MRI with integrated high-resolution multiparametric imaging of the prostatic fossa for comprehensive oncological staging of patients with prostate cancer: a pilot study

INTRODUCTION

The aim of the present study was to explore the clinical feasibility and reproducibility of a comprehensive whole-body ¹⁸F-PSMA-1007-PET/MRI protocol for imaging prostate cancer (PC) patients.

METHODS

Eight patients with high-risk biopsy-proven PC underwent a whole-body PET/MRI (3 h p.i.) including a multi-parametric prostate MRI after ¹⁸F-PSMA-1007-PET/CT (1 h p.i.) which served as reference. Seven patients presented with non-treated PC, whereas one patient presented with biochemical recurrence. SUV_mean-quantification was performed using a 3D-isocontour volume-of-interest. Imaging data was consulted for TNM-staging and compared with histopathology. PC was confirmed in 4/7 patients additionally by histopathology after surgery. PET-artifacts, co-registration of pelvic PET/MRI and MRI-data were assessed (PI-RADS 2.0).

RESULTS

The examinations were well accepted by patients and comprised 1 h. SUV_mean-values between PET/CT (1 h p.i.) and PET/MRI (3 h p.i.) were significantly correlated (p < 0.0001, respectively) and similar to literature of ¹⁸F-PSMA-1007-PET/CT 1 h vs 3 h p.i. The dominant intraprostatic lesion could be detected in all seven patients in both PET and MRI. T2c, T3a, T3b and T4 features were detected complimentarily by PET and MRI in five patients. PET/MRI demonstrated moderate photopenic PET-artifacts surrounding liver and kidneys representing high-contrast areas, no PET-artifacts were observed for PET/CT. Simultaneous PET-readout during prostate MRI achieved optimal co-registration results.

CONCLUSIONS

The presented ¹⁸F-PSMA-1007-PET/MRI protocol combines efficient whole-body assessment with high-resolution co-registered PET/MRI of the prostatic fossa for comprehensive oncological staging of patients with PC.

Improving postoperative radiotherapy following radical prostatectomy

INTRODUCTION

Prostate cancer has one of the highest incidences in the world, with good curative treatment options like radiotherapy and radical prostatectomy. Unfortunately, about 30% of the patients initially treated with curative intent will develop a recurrence and need adjuvant treatment. Five randomized trials covered the role of postoperative radiotherapy after radical prostatectomy, but there is still a lot of debate about which patients should receive postoperative radiotherapy. Areas covered: This review will give an overview on the available literature concerning post-operative radiotherapy following radical prostatectomy with an emphasis on the five randomized trials. Also, new imaging techniques like prostate-specific membrane antigen positron emission tomography (PSMA-PET) and multiparametric magnetic resonance imaging (mp-MRI) and the development of biomarkers like genomic classifiers will be discussed in the search for an improved selection of patients who will benefit from postoperative radiotherapy following radical prostatectomy. With new treatment techniques like Intensity Modulated Radiotherapy, toxicity profiles will be kept low. Expert commentary: Patients with biochemical recurrence following radical prostatectomy with an early rise in prostate-specific antigen (PSA) will benefit most from postoperative radiotherapy. In this way, patients with only high risk pathological features can avoid unnecessary treatment and toxicity, and early intervention in progressing patients would not compromise the outcome.

Oligometastases from prostate cancer: local treatment with stereotactic body radiotherapy (SBRT)

Background

The impact of local tumor ablative therapy in oligometastasized prostate cancer (PC) is still under debate. To gain data for this approach, we evaluated oligometastasized PC patients receiving stereotactic body radiotherapy (SBRT) to bone metastases.

Methods

In this retrospective study, 15 oligometastasized PC patients with a total of 20 bone metastases were evaluated regarding biochemical progression-free survival (PSA-PFS), time to initiation of ADT, and local control rate (LCR). Three patients received concomitant androgen deprivation therapy (ADT).

Results

The median follow-up after RT was 22.5 months (range 7.0–53.7 months). The median PSA-PFS was 6.9 months (range 1.1–28.4 months). All patients showing a decrease of PSA level after RT of at least factor 10 reveal a PSA-PFS of >12 months. Median PSA-PFS of this sub-group was 23.1 months (range 12.1–28.4 months). Local PFS (LPFS) after 2 years was 100%. One patient developed a local failure after 28.4 months. Median distant PFS (DPFS) was 7.36 months (range 1.74–54.34 months). The time to initiation of ADT in patients treated without ADT was 9.3 months (range 2.6–36.1 months). In all patients, the time to intensification of systemic therapy or the time to initiation of ADT increased from 9.3 to 12.3 months (range 2.6–36.1 months). Gleason-Score, ADT or the localization of metastasis had no impact on PFS or time to intensification of systemic therapy. No SBRT related acute or late toxicities were observed.

Conclusion

Our study shows that SBRT of bone metastases is a highly effective therapy with an excellent risk-benefit profile. However, PFS was limited due to a high distant failure rate implying the difficulty for patient selection for this oligometastatic concept. SBRT offers high local cancer control rates in bone oligometastases of PC and should be evaluated with the aim of curation or to delay modification of systemic treatment.