Value of 111 In-prostate-specific membrane antigen (PSMA)-radioguided surgery for salvage lymphadenectomy in recurrent prostate cancer: correlation with histopathology and clinical follow-up

Radioguided surgery for lymph node metastases in prostate cancer

PURPOSE OF REVIEW

This review highlights recent advancements in radioguided surgery (RGS) for prostate cancer. Our objective is to provide expert insights into the state of research, as reflected in the selected articles, and to offer perspectives on the clinical implications and future directions that emerge from this rapidly evolving domain.

RECENT FINDINGS

Key findings include the potential of PSMA-RGS surgery to improve the detection of lymph node invasion in primary prostate cancer, to guide successful removal of metastatic lesions in oligorecurrent patients with acceptable complications, and the feasibility of robot-assisted PSMA-RGS using a miniaturized gamma probe. Additionally, the development of novel PSMA ligands and the integration of fluorescence imaging offer promising improvements in imaging and surgical guidance.

SUMMARY

PSMA-RGS is an emerging approach that shows promise for improving lymph node assessment and treatment outcomes in prostate cancer. However, its effect on cancer-specific as well as overall survival are still being investigated, and PSMA-targeted surgery remains an area of active research.

Biochemical Response of <0.1 ng/ml Predicts Therapy-free Survival of Prostate Cancer Patients following Prostate-specific Membrane Antigen-targeted Salvage Surgery

BACKGROUND

In a subset of patients with oligorecurrent prostate cancer (PCa), salvage surgery with prostate-specific membrane antigen (PSMA) radioguided surgery (PSMA-RGS) seems to be of value.

OBJECTIVE

To evaluate whether a lower level of postoperative prostate-specific antigen (PSA; <0.1 ng/ml) is predictive of therapy-free survival (TFS) following salvage PSMA-RGS.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study evaluated patients with biochemical recurrence after radical prostatectomy and oligorecurrent PCa on PSMA positron emission tomography treated with PSMA-RGS in three tertiary care centers (2014-2022).

INTERVENTION

PSMA-RGS.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Postsalvage surgery PSA response was categorized as <0.1, 0.1-<0.2, or >0.2 ng/ml. Kaplan-Meier and multivariable Cox regression models evaluated TFS according to PSA response.

RESULTS AND LIMITATIONS

Among 553 patients assessed, 522 (94%) had metastatic soft tissue lesions removed during PSMA-RGS. At 2-16 wk after PSMA-RGS, 192, 62, and 190 patients achieved PSA levels of <0.1, 0.1-<0.2, and >0.2 ng/ml, respectively. At 2 yr of follow-up, TFS rate was 81.1% versus 56.1% versus 43.1% (p < 0.001) for patients with PSA <0.1 versus 0.1-<0.2 versus >0.2 ng/ml. In multivariable analyses, PSA levels of 0.1-0.2 ng/ml (hazard ratio [HR]: 1.9, confidence interval [CI]: 1.1-3.1) and ≥0.2 ng/ml (HR: 3.2, CI: 2.2-4.6, p < 0.001) independently predicted the need for additional therapy after PSMA-RGS. The main limitation is the lack of a control group.

CONCLUSIONS

For patients after salvage PSMA-RGS, a lower biochemical response (PSA <0.1 ng/ml) seems to predict longer TFS. This insight may help in counseling patients postoperatively as well as guiding the timely selection of additional therapy.

PATIENT SUMMARY

We studied what happened to prostate cancer patients in three European centers who had salvage surgery using a special method called prostate-specific membrane antigen-targeted radioguidance. We found that patients who had low prostate-specific antigen levels soon after surgery were less likely to need further treatment for a longer time.

Strong Correlation Between SUVmax on PSMA PET/CT and Numeric Drop-In γ-Probe Signal for Intraoperative Identification of Prostate Cancer Lesions

Prostate-specific membrane antigen (PSMA) PET is used to select patients with recurrent prostate cancer for metastasis-directed therapy. A surgical approach can be achieved through radioguided surgery (RGS), using a Drop-In γ-probe that traces lesions that accumulate the radioactive signal. With the aim of guiding patient selection for salvage surgery, we studied the correlation between the SUVmax of lesions on preoperative PSMA PET/CT and their intraoperative counts/s measured using the Drop-In γ-probe. Methods: A secondary analysis based on the prospective, single-arm, and single-center feasibility study was conducted (NCT03857113). Patients (n = 29) with biochemical recurrence after previous curative-intent therapy and a maximum of 3 suggestive lesions within the pelvis on preoperative PSMA PET/CT were included. Patients treated with androgen deprivation therapy within 6 mo before surgery were excluded. All patients received an intravenous injection of 99mTc-PSMA-I&S 1 d before surgery. Radioguidance was achieved using a Drop-In γ-probe. Correlation was determined using the Spearman rank correlation coefficient (ρs). Subgroup analysis was based on the median SUVmax Results: In total, 33 lesions were visible on the PSMA PET/CT images, with a median overall SUVmax of 6.2 (interquartile range [IQR], 4.2-9.7). RGS facilitated removal of 31 lesions. The median Drop-In counts/s were 134 (IQR, 81-220) in vivo and 109 (IQR, 72-219) ex vivo. The intensity of the values correlated with SUVmax (ρs = 0.728 and 0.763, respectively; P < 0.001). Subgroup analysis based on median SUVmax in the group with an SUVmax of less than 6 showed no statistically significant correlation with the numeric signal in vivo (ρs = 0.382; P = 0.221) or the signal-to-background-ratio (ρs = 0.245; P = 0.442), whereas the group with an SUVmax of 6 or more showed respective statistically significant positive correlations (ρs = 0.774 [P < 0.001] and ρs = 0.647 [P = 0.007]). Conclusion: Our findings indicate that there is a direct relation between SUVmax on PSMA PET/CT and the readout recorded by the surgical Drop-In probe, thereby indicating that SUVmax can be used to select patients for PSMA RGS. For more definitive subgroup definitions for treatment recommendations, further studies are necessary to validate the present findings.

Prostate-specific membrane antigen radioguided surgery with negative histopathology: an in-depth analysis

PURPOSE

To identify reasons for negative histopathology of specimens from prostate-specific membrane antigen (PSMA) radioguided surgery (PSMA-RGS) in recurrent prostate cancer (PCa) after prostatectomy.

METHODS

Of 302 patients who underwent PSMA-RGS, 17 (5.6%) demonstrated a negative histopathology. Preoperative data, PSMA PET, PSMA SPECT, and follow-up information were analyzed retrospectively to differentiate true/false positive (TP/FP) from true/false negative (TN/FN) lesions.

RESULTS

The median prostate-specific antigen at PET was 0.4 ng/ml (interquartile range [IQR] 0.3-1.2). Twenty-five index lesions (median short axis 7 mm, IQR 5-8; median long-axis 12 mm, IQR 8-17) had a median SUVmax of 4 (IQR 2.6-6; median PSMA expression score 1, IQR 1-1). Six lesions were TP, twelve were FP, one was TN, and six remained unclear. All TP lesions were in the prostatic fossa or adjacent to the internal iliac arteries. Three suspected local recurrences were FP. All FP lymph nodes were located at the distal external iliac arteries or outside the pelvis. A low PSMA-expressing TN node was identified next to a common iliac artery. Unclear lesions were located next to the external iliac arteries or outside the pelvis.

CONCLUSION

In most cases with a negative histopathology from PSMA-RGS, lesions were FP on PSMA PET. Unspecific uptake should be considered in low PSMA-expressing lymph nodes at the distal external iliac arteries or outside the pelvis, especially if no PSMA-positive lymph nodes closer to the prostatic fossa are evident. Rarely, true positive metastases were missed by surgery or histopathology.

Delphi consensus project on prostate-specific membrane antigen (PSMA)-targeted surgery-outcomes from an international multidisciplinary panel

PURPOSE

Prostate-specific membrane antigen (PSMA) is increasingly considered as a molecular target to achieve precision surgery for prostate cancer. A Delphi consensus was conducted to explore expert views in this emerging field and to identify knowledge and evidence gaps as well as unmet research needs that may help change practice and improve oncological outcomes for patients.

METHODS

One hundred and five statements (scored by a 9-point Likert scale) were distributed through SurveyMonkey®. Following evaluation, a consecutive second round was performed to evaluate consensus (16 statements; 89% response rate). Consensus was defined using the disagreement index, assessed by the research and development project/University of California, Los Angeles appropriateness method.

RESULTS

Eighty-six panel participants (72.1% clinician, 8.1% industry, 15.1% scientists, and 4.7% other) participated, most with a urological background (57.0%), followed by nuclear medicine (22.1%). Consensus was obtained on the following: (1) The diagnostic PSMA-ligand PET/CT should ideally be taken < 1 month before surgery, 1-3 months is acceptable; (2) a 16-20-h interval between injection of the tracer and surgery seems to be preferred; (3) PSMA targeting is most valuable for identification of nodal metastases; (4) gamma, fluorescence, and hybrid imaging are the preferred guidance technologies; and (5) randomized controlled clinical trials are required to define oncological value. Regarding surgical margin assessment, the view on the value of PSMA-targeted surgery was neutral or inconclusive. A high rate of "cannot answer" responses indicates further study is necessary to address knowledge gaps (e.g., Cerenkov or beta-emissions).

CONCLUSIONS

This Delphi consensus provides guidance for clinicians and researchers that implement or develop PSMA-targeted surgery technologies. Ultimately, however, the consensus should be backed by randomized clinical trial data before it may be implemented within the guidelines.

Safety and efficiency of repeat salvage lymph node dissection for recurrence of prostate cancer using PSMA-radioguided surgery (RGS) after prior salvage lymph node dissection with or without initial RGS support

BACKGROUND AND OBJECTIVE

Metastasis-directed therapy is a feasible option for low PSA, recurrent locoregional metastatic prostate cancer. After initial salvage surgery, patients with good response might consider a repeat salvage surgery in case of recurrent, isolated, and PSMA-positive metastases. This analysis aimed to evaluate the oncological outcome and safety of repeat PSMA-targeted radioguided surgery (RGS) after either prior RGS or "standard" salvage lymph node dissection (SLND).

MATERIALS AND METHODS

We identified 37 patients undergoing repeat RGS after prior SLND (n = 21) (SLND-RGS) or prior RGS (n = 16) (RGS-RGS) between 2014 and 2021 after initial radical prostatectomy with or without pelvic radiation therapy at two German tertiary referral centers. Kaplan-Meier analyses and uni-/multivariable Cox regression models were used to investigate factors associated with biochemical recurrence-free survival (BRFS) and treatment-free survival (TFS) after repeat salvage surgery.

RESULTS AND LIMITATIONS

Complete Biochemical Response (cBR, PSA < 0.2 ng/ml) was observed in 20/32 patients (5 NA). Median overall BRFS [95% confidence interval (CI)] after repeat salvage surgery was 10.8 months (mo) (5.3-22). On multivariable regression, only age (HR 1.09, 95% CI 1.01-1.17) and preoperative PSA (HR 1.23, 95% CI 1.01-1.50) were associated with shorter BRFS, although PSA (HR 1.16, 95% CI 0.99-1.36) did not achieve significant predictor status in univariable analysis before (p value = 0.07). Overall, one year after second salvage surgery, 89% of the patients (number at risk: 19) did not receive additional treatment and median TFS was not reached. Clavien-Dindo grade > 3a complications were observed in 8% (3/37 patients). Limitations are the retrospective evaluation, heterogeneous SLND procedures, lack of long-term follow-up data, and small cohort size.

CONCLUSION

In this study, repeat RGS was safe and provided clinically meaningful biochemical recurrence- and treatment-free intervals for selected cases. Patients having low preoperative PSA seemed to benefit most of repeat RGS, irrespective of prior SLND or RGS or the time from initial RP/first salvage surgery.

State of the Art in Prostate-specific Membrane Antigen-targeted Surgery-A Systematic Review

Context

Identifying malignant tissue and leaving adjacent structures undisturbed constitute an ongoing challenge in prostate cancer (PCa) surgery. Image and radioguided surgical technologies targeting the prostate-specific membrane antigen (PSMA) receptor may facilitate identification and removal of diseased tissue.

Objective

To perform a systematic review of the clinical studies on PSMA-targeted surgery.

Evidence acquisition

The MEDLINE (OvidSP), Embase.com, and Cochrane Library databases were searched. Identified reports were critically appraised according to the Idea, Development, Exploration, Assessment, Long-term framework criteria. The risk of bias (RoB) was assessed as per the Risk Of Bias In Non-randomized Studies-of Interventions tool. The strengths and limitations of the techniques and corresponding oncological outcomes were extracted as areas of interest. Data were reported according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines.

Evidence synthesis

In total, 29 reports were selected, including eight prospective studies, 12 retrospective analyses, and nine case reports, all with a high or an unclear RoB. In 72.4% of studies, PSMA targeting was achieved via radioguided surgery (RGS), predominantly using ^99mTc-PSMA-I&S (66.7%). Hybrid approaches that complement RGS with optical guidance are emerging. The majority of studies retrieved were pilot studies with a short follow-up. In 13 reports, salvage lymph node surgery was discussed (44.8%). In 12 more recent reports (41.4%), PSMA targeting was studied in primary PCa surgery (50.0% lymph nodes and 50.0% surgical margins), and four studied both primary and salvage surgery (13.8%). Overall, specificity was higher than sensitivity (median 98.9% and 84.8%, respectively). Oncological outcomes were discussed only in reports on the use of ^99mTc-PSMA-I&S in salvage surgery (median follow-up of 17.2 mo). A decline in prostate-specific antigen level of >90% ranged from 22.0% to 100.0%, and biochemical recurrence ranged from 50.0% to 61.8% of patients.

Conclusions

In PSMA-targeted surgery, most studies address salvage PSMA-RGS using ^99mTc-PSMA-I&S. Available evidence suggests that the specificity of intraoperative PSMA targeting is higher than the sensitivity. The studies that included follow-up did not yet objectify a clear oncological benefit. Lacking solid outcome data, PSMA-targeted surgery remains investigational.

Patient summary

In this paper, we review recent advances in prostate-specific membrane antigen (PSMA)-targeted surgery, which is used to help identify and remove prostate cancer. We found good evidence to suggest that PSMA targeting helps identify prostate cancer during surgery. The oncological benefits have yet to be investigated further.

67 Ga-PSMA I&T for Radioguided Surgery of Lymph Node Metastases in Patients With Biochemical Recurrence of Prostate Cancer

PURPOSE

Radioguided lymph node dissection in patients with prostate cancer, and suffering from biochemical recurrence has been described thoroughly during the past few years. Several prostate-specific membrane antigen (PSMA)-directed ligands labeled with 111 In, 99m Tc, and 68 Ga have been published; however, limitations regarding availability, short half-life, high costs, and unfavorable high energy might restrict frequent use. This study aims at introducing 67 Ga as a promising radionuclide for radioguided surgery.

METHODS

Retrospective analysis was performed on 6 patients with 7 PSMA-positive lymph node metastases. 67 Ga-PSMA I&T (imaging and therapy) was synthesized in-house and intravenously applied according to §13 2b of the German Medicinal Products Act. Radioguided surgery was performed 24 hours after injection of 67 Ga-PSMA I&T using a gamma probe. Patient urine samples were collected. Occupational and waste dosimetry was performed to describe hazards arising from radiation.

RESULTS

67 Ga-PSMA application was tolerated without adverse effects. Five of 7 lymph nodes were detected on 22-hour SPECT/CT in 4 of 6 patients. During surgery, all 7 lymph node metastases were identified by positive gamma probe signal. Relevant accumulation of 67 Ga was observed in lymph node metastases (32.1 ± 15.1 kBq). Histology analysis of near-field lymph node dissection revealed more lymph node metastases than PET/CT (and gamma probe measurements) identified. Waste produced during inpatient stay required decay time of up to 11 days before reaching exemption limits according to German regulations.

CONCLUSIONS

Radioguided surgery using 67 Ga-PSMA I&T is a safe and feasible option for patients suffering from biochemical recurrence of prostate cancer. 67 Ga-PSMA I&T was successfully synthesized according to Good Manufacturing Practice guidelines. Radioguided surgery with 67 Ga-PSMA I&T does not lead to relevant radiation burden to urology surgeons and represents a novel interdisciplinary approach in nuclear medicine and urology.

Delayed Imaging Improves Lesion Detectability in [99mTc]Tc-PSMA-I&S SPECT/CT in Recurrent Prostate Cancer

Our objective was to compare the ability to detect histopathologically confirmed lymph node metastases by early and delayed [^99mTc]Tc-PSMA-I&S SPECT/CT in early biochemically recurrent prostate cancer. Methods: We retrospectively analyzed 222 patients selected for radioguided surgery using [^99mTc]Tc-PSMA-I&S SPECT/CT at different time points after injection (≤4 h and >15 h). In total, 386 prostate-specific membrane antigen (PSMA) PET predetermined lesions were analyzed on SPECT/CT using a 4-point scale, and the results were compared between early and late imaging groups, with uni- and multivariate analyses performed including prostate-specific antigen, injected [^99mTc]Tc-PSMA-I&S activity, Gleason grade group, initial TNM stage, and, stratified by size, PSMA PET/CT-positive lymph nodes. PSMA PET/CT findings served as the standard of reference. Results: [^99mTc]Tc-PSMA-I&S SPECT/CT had a significantly higher positivity rate for detecting lesions in the late than the early imaging group (79%, n = 140/178, vs. 27%, n = 12/44 [P < 0.05] on a patient basis; 60%, n = 195/324, vs. 21%, n = 13/62 [P < 0.05] on a lesion basis). Similar positivity rates were found when lesions were stratified by size. Multivariate analysis found that SUV_max on PSMA PET/CT and the uptake time of [^99mTc]Tc-PSMA-I&S were independent predictors for lesion detectability on SPECT/CT. Conclusion: Late imaging (>15 h after injection) should be preferred when [^99mTc]Tc-PSMA-I&S SPECT/CT is used for lesion detection in early biochemical recurrence of prostate cancer. However, the performance of PSMA SPECT/CT is clearly inferior to that of PSMA PET/CT.

Clinical advancement of precision theranostics in prostate cancer

Theranostic approaches with positron emission tomography/computed tomography (PET/CT) or PET/magnetic resonance imaging (PET/MRI) molecular imaging probes are being implemented clinically in prostate cancer (PCa) diagnosis and imaging-guided precision surgery. This review article provides a comprehensive summary of the rapidly expanding list of molecular imaging probes in this field, including their applications in early diagnosis of primary prostate lesions; detection of lymph node, skeletal and visceral metastases in biochemical relapsed patients; and intraoperative guidance for tumor margin detection and nerve preservation. Although each imaging probe shows preferred efficacy in some applications and limitations in others, the exploration and research efforts in this field will eventually lead to improved precision theranostics of PCa.

Clinical Pharmacology of Radiotheranostics in Oncology

The combined use of diagnostic and therapeutic radioligands with the same molecular target, also known as theranostics, enables accurate patient selection, targeted therapy, and prediction of treatment response. Radioiodine, bone-seeking radioligands and norepinephrine analogs have been used for many years for diagnostic imaging and radioligand therapy of thyroid carcinoma, bone metastases, pheochromocytoma, paraganglioma, and neuroblastoma, respectively. In recent years, radiolabeled somatostatin analogs and prostate-specific membrane antigen ligands have shown clinical efficacy in the treatment of neuroendocrine tumors and prostate cancer, respectively. Several candidate compounds are targeting novel theranostic targets such as fibroblast activation protein, C-X-C chemokine receptor 4, and gastrin-releasing peptide receptor. In addition, several strategies to improve efficacy of radioligand therapy are being evaluated, including dosimetry-based dose optimization, multireceptor targeting, upregulation of target receptors, radiosensitization, pharmacogenomics, and radiation genomics. Design and evaluation of novel radioligands and optimization of dose and dose schedules, within the complex context of individualized multimodal cancer treatment, requires a multidisciplinary approach that includes clinical pharmacology. Significant increases in the use of these radiopharmaceuticals in routine oncological practice can be expected, which will have major impact on patient care as well as (radio)pharmacy utilization.

Feasibility of 99mTc-MIP-1404 for SPECT/CT Imaging and Subsequent PSMA-Radioguided Surgery in Early Biochemically Recurrent Prostate Cancer: A Case Series of 9 Patients

This case series evaluated the feasibility of prostate-specific membrane antigen (PSMA)-radioguided surgery (RGS) with ^99mTc-MIP-1404 in recurrent prostate cancer. Methods: Nine patients with PSMA-positive lesions on PET/CT received ^99mTc-MIP-1404 (median, 747 MBq; interquartile range [IQR], 710-764 MBq) 17.2 h (IQR, 16.9-17.5 h) before SPECT/CT and 22.3 h (IQR, 20.8-24.0 h) before RGS. Results: Seventeen PSMA-positive lesions were detected on PET/CT (median short-axis diameter, 4 mm; IQR, 3-6 mm; median SUV_max, 8.9; IQR, 5.2-12.6). Nine of 17 (52.9%) were visible on SPECT/CT (median SUV_max, 13.8; IQR, 8.0-17.9). Except for 2 foci, all PET/CT-positive findings demonstrated intraoperative count rates above the background level (median count, 31; IQR, 17-89) and were lymph node metastases. Moreover, PSMA-RGS identified 2 additional metastases compared with PET/CT. Prostate-specific antigen values decreased after RGS in 6 of 9 patients (67%). Conclusion: PSMA-RGS with ^99mTc-MIP-1404 identified lymph node metastases in all patients, including 2 additional lesions compared with PET/CT.

Cohort Study of Oligorecurrent Prostate Cancer Patients: Oncological Outcomes of Patients Treated with Salvage Lymph Node Dissection via Prostate-specific Membrane Antigen-radioguided Surgery

BACKGROUND

In a subset of patients with recurrent oligometastatic prostate cancer (PCa) salvage surgery with prostate-specific membrane antigen (PSMA)-targeted radioguidance (PSMA-RGS) might be of value.

OBJECTIVE

To evaluate the oncological outcomes of salvage PSMA-RGS and determine the predictive preoperative factors of improved outcomes.

DESIGN, SETTING, AND PARTICIPANTS

A cohort study of oligorecurrent PCa patients with biochemical recurrence (BCR) after radical prostatectomy and imaging with PSMA positron emission tomography (PET), treated with PSMA-RGS in two tertiary care centers (2014-2020), was conducted.

INTERVENTION

PSMA-RGS.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Kaplan-Meier and multivariable Cox regression models were used to assess BCR-free (BFS) and therapy-free (TFS) survival. Postoperative complications were classified according to Clavien-Dindo.

RESULTS AND LIMITATIONS

Overall, 364 patients without concomitant treatment were assessed. At PSMA-RGS, metastatic soft-tissue PCa lesions were removed in 343 (94%) patients. At 2-16 wk after PSMA-RGS, 165 patients reached a prostate-specific antigen (PSA) level of <0.2 ng/ml. Within 3 mo, 24 (6.6%) patients suffered from Clavien-Dindo complications grade III-IV. At 2 yr, BFS and TFS rates were 32% and 58%, respectively. In multivariable analyses, higher preoperative PSA (hazard ratio [HR]: 1.07, 95% confidence interval [CI]: 1.02-1.12), higher number of PSMA-avid lesions (HR: 1.23, CI: 1.08-1.40), multiple (pelvic plus retroperitoneal) localizations (HR: 1.90, CI: 1.23-2.95), and retroperitoneal localization (HR: 2.04, CI: 1.31-3.18) of lesions in preoperative imaging were independent predictors of BCR after PSMA-RGS. The main limitation is the lack of a control group.

CONCLUSIONS

As salvage surgery in oligorecurrent PCa currently constitutes an experimental treatment approach, careful patient selection is mandatory based on life expectancy, low PSA values, and low number of PSMA PET-avid lesions located in the pelvis.

PATIENT SUMMARY

We looked at the outcomes from prostate cancer patients with recurrent disease after radical prostatectomy. We found that surgery may be an opportunity to prolong treatment-free survival, but patient selection criteria need to be very narrow.

Prostate-specific membrane antigen-directed imaging and radioguided surgery with single-photon emission computed tomography: state of the art and future outlook

INTRODUCTION

Prostate-specific membrane antigen (PSMA) has emerged as a highly relevant target for prostate cancer (PC) diagnosis and therapy. PSMA inhibitors targeting PSMA-enzymatic domain have been successfully labeled with radionuclides emitting positrons or gamma-photons, thus obtaining tracers suitable for imaging with positron emission computed tomography (PET/CT) or single-photon emission tomography (SPECT).

AREAS COVERED

The different approaches for obtaining PSMA-ligands labeled with gamma-emitting nuclides (^99mTc or¹¹¹In) are reviewed. Furthermore, the applications of ^99mTc/¹¹¹In-PSMA SPECT for the imaging of PC patients in different clinical settings (staging or biochemical recurrence) are covered. Lastly, the employment of PSMA-targeted SPECT tracers for radioguided surgery (RGS) during primary or salvage lymphadenectomy is discussed.

EXPERT OPINION

RGS provided satisfying preliminary results in both primary and salvage lymphadenectomy, allowing to discriminate between pathological and non-pathological nodes with high accuracy, although prospective studies with larger cohorts are needed to further validate this surgical approach. The potential of PSMA-targeted SPECT/CT has not been fully explored yet, but it might represent a relatively cost-effective alternative to PSMA PET/CT in limited resource environments. In this perspective, the implementation of novel SPECT technologies or algorithms, such as semiconductor-ionization detectors or resolution recovery reconstruction, will be topic of future investigation.

Advances in PSMA-targeted therapy for prostate cancer

Prostate-specific membrane antigen (PSMA), a transmembrane glycoprotein located on the cell membrane, is specifically and highly expressed in prostate cancer (PCa). Besides, its expression level is related to tumor invasiveness. As a molecular target of PCa, PSMA has been extensively studied in the past two decades. Currently, a great deal of evidence suggests that significant progresses have been made in the PSMA-targeted therapy of PCa. Herein, different PSMA-targeted therapies for PCa are reviewed, including radioligand therapy (¹⁷⁷Lu-PSMA-RLT, ²²⁵Ac-PSMA-RLT), antibody-drug conjugates (MLN2704, PSMA-MMAE, MEDI3726), cellular immunotherapy (CAR-T, CAR/NK-92, PSMA-targeted BiTE), photodynamic therapy, imaging-guided surgery (radionuclide-guided surgery, fluorescence-guided surgery, multimodal imaging-guided surgery), and ultrasound-mediated nanobubble destruction.

Prostate-Specific Membrane Antigen Radioguided Surgery for Salvage Pelvic Lymph Node Dissection in a Man With Prostate Cancer

ABSTRACT

A 75-year-old man with evidence of recurrent prostate cancer on 68Ga-prostate-specific membrane antigen (PSMA) PET/CT after radical prostatectomy was referred to our department for 99mTc-PSMA radioguided surgery. Intraoperatively, lymph nodes with high count rates were localized using a handheld gamma probe. High-count specimens were resected from the exact locations as reported by 68Ga-PSMA PET/CT. The total prostate-specific antigen value decreased 6 weeks after surgery. Our case shows the feasibility of radioguided surgery with 99mTc-PSMA for salvage lymphadenectomy in prostate cancer.

Expression of Prostate Specific Membrane Antigen (PSMA) in Breast Cancer

Background Prostate specific membrane antigen (PSMA) is a promising protein for breast cancer patients. It has not only been detected in prostate cancer but is also expressed by tumor cells and the endothelial cells of tumor vessels in breast cancer patients. PSMA plays a role in tumor progression and tumor angiogenesis. For this reason, a number of diagnostic and therapeutic methods to target PSMA have been developed. Method This paper provides a general structured overview of PSMA and its oncogenic potential, with a special focus on its role in breast cancer. This narrative review is based on a selective literature search carried out in PubMed and the library of Freiburg University Clinical Center. The following key words were used for the search: "PSMA", "PSMA and breast cancer", "PSMA PET/CT", "PSMA tumor progression". Relevant articles were explicitly read through, processed, and summarized. Conclusion PSMA could be a new diagnostic and therapeutic alternative, particularly for triple-negative breast cancer. It appears to be a potential predictive and prognostic marker.

Radiolabeled PSMA Inhibitors

PSMA has shown to be a promising target for diagnosis and therapy (theranostics) of prostate cancer. We have reviewed developments in the field of radio- and fluorescence-guided surgery and targeted photodynamic therapy as well as multitargeting PSMA inhibitors also addressing albumin, GRPr and integrin αvβ3. An overview of the regulatory status of PSMA-targeting radiopharmaceuticals in the USA and Europe is also provided. Technical and quality aspects of PSMA-targeting radiopharmaceuticals are described and new emerging radiolabeling strategies are discussed. Furthermore, insights are given into the production, application and potential of alternatives beyond the commonly used radionuclides for radiolabeling PSMA inhibitors. An additional refinement of radiopharmaceuticals is required in order to further improve dose-limiting factors, such as nephrotoxicity and salivary gland uptake during endoradiotherapy. The improvement of patient treatment achieved by the advantageous combination of radionuclide therapy with alternative therapies is also a special focus of this review.

Salvage lymph node dissection for prostate-specific membrane antigen (PSMA) positron emission tomography (PET)-identified oligometastatic disease

INTRODUCTION

The availability of prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) imaging, particularly in the setting of rising prostate-specific antigen (PSA) after definitive treatment, has led to oligometastatic prostate cancer being increasingly identified. Despite the enthusiasm surrounding treating oligometastatic disease, it has been relatively understudied. We sought to review our salvage lymphadenectomy experience in the PSMA PET/CT era.

METHODS

We retrospectively reviewed patients undergoing lymphadenectomy following curative-intent primary therapy with rising PSA who had undergone a PSMA PET/CT identifying oligometastatic disease (defined as ≤5 PSMA-avid lesions) between January 2016 and April 2020. The primary endpoint was complete response, defined as achieving a PSA <0.2 ng/ml without concomitant androgen deprivation therapy (ADT).

RESULTS

Twenty-two patients were included. Primary curative therapy included radical prostatectomy (86.4%) and brachytherapy (13.6%). Median PSA at salvage surgery was 1.72 ng/ml. Pelvic lymph node dissection was the most performed procedure (72.7%). Median node yield was 10.5, with a median of 1.5 positive nodes on pathology. Eight patients (36.4%) achieved PSA <0.2, with six (27.3%) remaining with PSA <0.2 after a median followup of 23.1 months. Nine (40.9%) had an initial PSA decline, but nadired ≥0.2, and in five (22.7%) the PSA rose immediately after surgery. Overall, ADT was started in seven patients (31.8%) at a median of 10.1 months post-salvage surgery.

CONCLUSIONS

In our series of salvage dissection for PSMA-PET-detected nodal oligometastases, approximately a third achieved PSA <0.2; yet, it was only durable in 27%. Prospective trials of salvage nodal radiation are ongoing, however, more prospective trials of salvage node dissection are needed.

Occupational radiation exposure of radiopharmacy-, nuclear medicine-, and surgical personnel during use of [99mTc]Tc-PSMA-I&S for prostate cancer surgery

Aim: The aim of this study was to estimate and subsequently measure the occupational radiation exposure for all personnel involved in the production, administration, imaging, or surgery with [^99mTc]Tc-PSMA-I&S, which has been introduced for identification of tumor-positive lymph nodes during salvage prostate cancer surgery Materials and Methods: The effective dose was estimated and subsequently measured with electronic personal dosimeters for the following procedures and personnel: labeling and quality control by the radiopharmacy technician, syringe preparation by the nuclear medicine laboratory technician, patient administration by the nuclear medicine physician, patient imaging by the nuclear medicine imaging technician, and robot-assisted laparoscopic salvage lymph node dissection attended by an anesthesiology technician, scrub nurse, surgical nurse, and surgeon. The dose rate of the patient was measured immediately after administration of [^99mTc]Tc-PSMA-I&S, after imaging, and after surgery. Results: The estimated dose per procedure ranged from 1.59x10-10 µSv (imaging technician) to 9.74 µSv (scrub nurse). The measured effective dose ranged from 0 to 5 µSv for all personnel during one procedure with [^99mTc]Tc-PSMA-I&S. The highest effective dose was received by the scrub nurse (3.2±1.3 µSv), whilst the lowest dose was measured for the surgical nurse (0.2±0.5 µSv). If a single scrub nurse would perform as much as 100 procedures with [^99mTc]Tc-PSMA-I&S in a year, the total effective dose would be 3.2x10-1 mSv/year. Immediately after administration, the dose rate at 50 cm from the patient was 18.5±1.6 µSv/h, which dropped to 1.8±0.3 µSv/h after imaging the following day and reducing even further to 0.56±0.33 µS/h after surgery. Conclusion: The effective dose for personnel involved in handling [^99mTc]Tc-PSMA-I&S is comparable to that of other ^99mTc-radiopharmaceuticals and therefore safe for imaging and radioguided surgery.

The role of fluorescent and hybrid tracers in radioguided surgery in urogenital malignancies

The increasing availability of new imaging technologies and tracers has enhanced the application of nuclear molecular imaging in urogenital interventions. In this context, preoperative nuclear imaging and radioactivity-based intraoperative surgical guidance have become important tools for the identification and anatomical allocation of tumor lesions and/or suspected lymph nodes. Fluorescence guidance can provide visual identification of the preoperatively defined lesions during surgery. However, the added value of fluorescence guidance is still mostly unknown. This review provides an overview of the role of fluorescence imaging in radioguided surgery in urogenital malignancies. The sentinel node (SN) biopsy procedure using hybrid tracers (radioactive and fluorescent component) serves as a prominent example for in-depth evaluation of the complementary value of radio- and fluorescence guidance. The first large patient cohort and long-term follow-up studies show: 1) improvement in the SN identification rate compared to blue dye; 2) improved detection of cancer-positive SNs; and 3) hints towards a positive effect on (biochemical) recurrence rates compared to extended lymph node dissection. The hybrid tracer approach also highlights the necessity of a preoperative roadmap in preventing incomplete resection. Recent developments focus on receptor-targeted approaches that allow intraoperative identification of tumor tissue. Here radioguidance is still leading, but fluorescent and hybrid tracers are also finding their way into the clinic. Emerging multiwavelength approaches that allow concomitant visualization of different anatomical features within the surgical field may provide the next step towards even more refined procedures.

Oligometastatic prostatic cancer recurrence: role of salvage lymph node dissection (sLND) and radiation therapy-stereotactic body radiation therapy (RT-SBRT)

PURPOSE OF REVIEW

Metastases directed therapy (MDT) is an increasingly utilized modality in patients with oligometastatic prostate cancer (OMPC) recurrence. The purpose of our review is to discuss the recent literature on the safety and oncologic outcomes of this treatment approach.

RECENT FINDINGS

Metastases directed therapy, in particular, stereotactic body radiation therapy (SBRT) and salvage lymph node dissection (sLND), has shown promising efficacy in patients with OMPC. Many case series report favorable outcomes with MDT as compared to hormonal deprivation therapy alone or surveillance. Of the few case series investigating the use of MDT as part of a multimodality approach in castrate-resistant OMPC, more favorable outcomes in comparison to the use of systemic treatment alone are reported.

SUMMARY

With the recent advances in imaging techniques, particularly molecular imaging, management of OMPC has progressed rapidly in the last few years. The feasibility and benefits of MDT in OMPC have been demonstrated in prospective and retrospective series. Further prospective studies investigating the role of MDT to define optimal patient subgroups and management strategies are warranted.

Contemporary update of SPECT tracers and novelties in radioguided surgery: a perspective based on urology

Recent technical advances and implementation of novel radiotracers have further increased the potential of radioguided surgery for a broad variety of malignancies. Indeed, the possibilities for future applications of novel radiotracers in diverse oncological strategies has become more promising than ever. This literature review aims to provide a contemporary update on a selected group of radiotracers and evaluates the usability of radioguided surgery and sentinel node procedures, focusing on most promising advances. For example, the impact of targeted radiotracers on prostate specific membrane antigen (PSMA), CD206 receptor-targeted agents (^99mTc-tilmanocept), and hybrid tracers adding fluorescence to radioguidance (ICG-^99mTc-nanocolloid) as well as targeting hypoxia-induced carbonic anhydrase IX (CAIX) will be covered. Furthermore, future outlooks on the implementation of gold nanoparticles (AuNP's), but also technical advances in improved radiotracer detection by hybrid gamma devices will be discussed.

99mTc-labelled PSMA ligand for radio-guided surgery in nodal metastatic prostate cancer: proof of principle

Purpose

Intraoperative identification of prostate cancer (PCa) lymph node (LN) metastases (LNM) detected by preoperative PSMA PET/CT may be facilitated by PSMA radio-guided surgery (RGS) with use of a γ-probe. Earlier we demonstrated excellent performance of the ¹¹¹In-labelled PSMA ligand DKFZ-617 ([¹¹¹In]In-PSMA-617) in RGS for ex situ distinction of LN vs LNM at lymphadenectomy (LA) at a single LN level. In comparison with indium-111, technetium-99m has better physical properties for γ-probe measurements, better availability and lower radiation exposure for patients and medical personnel. Against this background, we evaluated the uptake of ^99mTc-PSMA-I&S ligand at the level of single LN and its power to discriminate between unaffected LN and LNM.

Methods

Six patients with PCa with the suspicion of LNM on preoperative PSMA-PET/CT underwent [^99mTc]Tc-PSMA-I&S RGS (4 salvage LA, 2 primary LA) with intravenous injection of [^99mTc]Tc-PSMA-I&S 24 h prior to surgery. Resected samples were isolated manually aiming at the level of single LN. Uptake measurements were done ex situ with a high-purity germanium detector. Receiver operating characteristic (ROC) analysis was performed based on [^99mTc]Tc-PSMA-I&S uptake expressed as lean body mass standard uptake value (SUL).

Results

Separation of the tissue samples from 73 subregions resulted in 498 single samples. After final histopathology 356 LN, 160 LNM und 11 non-nodal PCa samples were identified. Median SUL of tumor-free samples (0.26) and samples with cancer (3.5) was significantly different (p < 0.0001). ROC analysis revealed an area under the curve (AUC) of 0.917 (95% CI 0.89–0.95). Using a SUL cutoff of 1.1, sensitivity, specificity, positive predictive value, and negative predictive values were 76.6%, 94.4%, 89.4% and 86.9%.

Conclusion

Ex situ analysis of [^99mTc]Tc-PSMA-I&S uptake at single LN level showed good diagnostic performance for the ex situ distinction of tumor-bearing vs tumor-free LN during RGS.

Prostate-Specific Membrane Antigen PET for Assessment of Primary and Recurrent Prostate Cancer with Histopathology as Reference Standard: A Systematic Review and Meta-Analysis

Prostate-specific membrane antigen PET is a promising diagnostic tool in prostate cancer. The gold standard for the detection of prostate tumor and lymph node metastases is histopathology. The aim of the present review was to investigate accuracy measures of ⁶⁸Ga/¹⁸F-labeled prostate-specific membrane antigen PET tracers in primary and recurrent prostate cancer with systematic sector-based histopathology as the reference standard. A systematic literature search was performed and 34 studies were included. Overall, prostate-specific membrane antigen PET showed high specificity, but variable sensitivity to localize known prostate cancer and detect pelvic lymph node metastases.

Mesorectal Lymph Node Metastases as Index Lesion in 68Ga-PSMA-PET/CT Imaging for Recurrent Prostate Cancer

Purpose: Several studies have demonstrated an advantage of ⁶⁸Ga-PSMA-PET/CT as staging modality for detection of prostate cancer (PCa) metastases. Data concerning metastatic manifestation and impact on PCa development of mesorectal lymph nodes (MLN) is limited. Our investigation describes MLN metastases as index lesion in ⁶⁸Ga-PSMA PET/CT imaging for recurrent PCa.

Methods: Twelve PCa patients with biochemical recurrence (BCR) after primary therapy who prospectively underwent a baseline ⁶⁸Ga-PSMA-PET/CT initially showed MLN metastases. Eight of these patients received a follow-up ⁶⁸Ga-PSMA-PET/CT to evaluate treatment response and further evolution. Prostate-specific antigen (PSA)-levels, changes in PSMA-uptake of MLN metastases and further ⁶⁸Ga-PSMA PET/CT findings were recorded.

Results: Median PSA at the first ⁶⁸Ga-PSMA-PET/CT was 5.39 ng/ml. In all patients therapeutic management changed after the first ⁶⁸Ga-PSMA-PET/CT. Androgen deprivation therapy (ADT) was initiated in seven of eight patients, one patient restarted initial ADT. Three patients additionally received salvage radiation therapy (sRT) including the prostatic lodge and docetaxel chemotherapy was started in one case. At follow-up, a decrease of PSA-level was detected in all patients (median 2.05 ng/ml) after median 10 months. In six of eight patients we observed a decrease or complete regress of PSMA-uptake in MLN in the follow-up ⁶⁸Ga-PSMA-PET/CT.

Conclusion: MLN metastases detected by ⁶⁸Ga-PSMA-PET/CT seem to be a relevant localization of tumor manifestation and may serve as index lesion in the treatment of recurrent PCa. Besides the known oncological benefits of ADT and sRT, in case of sole MLN metastases individualized therapy like salvage lymphadenectomy or RT with a defined radiation field could be options for these patients.

Interventional nuclear medicine: a focus on radioguided intervention and surgery

Within interventional nuclear medicine (iNM) a prominent role is allocated for the sub-discipline of radioguided surgery. Unique for this discipline is the fact that an increasing number of clinical indications (e.g. lymphatic mapping, local tumor demarcation and/or tumor receptor targeted applications) have been adopted into routine care. The clinical integration is further strengthened by technical innovations in chemistry and engineering that enhance the translational potential of radioguided procedures in iNM. Together, these features not only ensure ongoing expansion of iNM but also warrant a lasting clinical impact for the sub-discipline of radioguided surgery.

Salvage Surgery in Patients with Local Recurrence After Radical Prostatectomy

BACKGROUND

Since the introduction of prostate-specific membrane antigen (PSMA) positron emission tomography (PET) imaging, isolated local recurrence after radical prostatectomy (RP) can be delineated accurately.

OBJECTIVE

To describe and evaluate surgical technique, biochemical response, and therapy-free survival (TFS) after salvage surgery in patients with local recurrence in the seminal vesicle bed.

DESIGN, SETTING, AND PARTICIPANTS

We retrospectively assessed 40 patients treated with open salvage surgery in two centres (11/2014-02/2020). All patients presented with biochemical recurrence (BCR) after RP with a singular local recurrence at PSMA PET imaging. Thirty-three (82.5%) patients received previous salvage radiation therapy.

SURGICAL PROCEDURE

Open salvage surgery with PSMA radioguidance.

MEASUREMENTS

Prostate-specific antigen (PSA) nadir and percentage of patients with complete biochemical response (cBR) without further treatment (PSA < 0.2 ng/ml) after 6-16 wk were assessed. BCR-free survival and TFS were calculated using Kaplan-Meier estimates. Clavien-Dindo complications were evaluated.

RESULTS AND LIMITATIONS

Prior to salvage surgery, median PSA was 0.9 ng/ml (interquartile range [IQR]: 0.5-1.7 ng/ml). Postoperatively, median PSA nadir was 0.1 ng/ml (IQR: 0-0.4 ng/ml). In 31 (77.5%) patients, cBR was observed. During the median follow-up of 24.4 months, 22 (55.0%) patients experienced BCR and 12 (30.0%) received further therapy. At 1 yr of follow-up, BCR-free survival rate was 62.2% and TFS rate was 88.3%. Three (7.5%) Clavien-Dindo grade III complications were observed. The main limitations are the retrospective design, short follow-up, and lack of a control group.

CONCLUSIONS

Salvage surgery of local recurrence within the seminal vesicle bed is feasible. It may present an opportunity in selected, locally recurrent patients to prolong BCR-free survival and increase TFS. Further studies are needed to confirm our findings.

PATIENT SUMMARY

We looked at the outcomes from prostate cancer patients with locally recurrent disease after radical prostatectomy and radiotherapy. We found that surgery in well-selected patients may be an opportunity to prolong treatment-free survival.

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

INTRODUCTION

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

EVIDENCE ACQUISITION

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

EVIDENCE SYNTHESIS

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

CONCLUSIONS

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

Future of Theranostics: An Outlook on Precision Oncology in Nuclear Medicine

Molecular alterations in malignant disease result in the expression or upregulations of various targets that can be used for imaging and treatment with radiopharmaceuticals. This theranostic principle has acquired greater importance in personalized medicine in recent years, particularly in oncology, where advanced tumors can be treated effectively with low side effects. Since the pioneering use of ¹³¹I in differentiated thyroid cancer in the 1940s, remarkable achievements in nuclear medicine endoradiotherapy have been demonstrated, mainly in the treatment of neuroendocrine neoplasms by using ¹⁷⁷Lu-labeled somatostatin analogs or in the treatment of advanced prostate cancer using prostate-specific membrane antigen-directed radionuclide therapy. Besides that, this review focuses on promising novel radiopharmaceuticals and describes their preclinical and clinical status. Radiolabeled antibodies, such as ¹³¹I-omburtamab directed against the B7-H3 protein on the surface of neuroblastoma cells; HuMab-5B1, a ⁸⁹Zr/¹⁷⁷Lu-labeled antibody for the treatment of CA19-9-expressing malignancies; and ¹⁷⁷Lu-lilotomab, a CD37 antibody for the treatment of B-cell lymphomas, are being highlighted. The neurotensin receptor ligand ¹¹¹In/¹⁷⁷Lu-3B-227 has demonstrated high potential in imaging and therapy for several malignancies (e.g., pancreatic adenocarcinomas). Targeting of the fibroblast activation protein is currently being explored for different tumor entities using PET imaging with the fibroblast activation protein inhibitor (FAPI) ⁶⁸Ga-FAPI-04, and the first therapeutic applications of ⁹⁰Y-FAPI-04 have been applied. After 2 decades of rapid development in theranostics, a variety of new targets are available for further clinical investigation.

Review on 99mTc radiopharmaceuticals with emphasis on new advancements

Rapid imaging acquisition, high spatial resolution and sensitivity, powered by advancements in solid-state detector technology, are significantly changing the perspective of single photon emission tomography (SPECT). In particular, this evolutionary step is fueling a rediscovery of technetium-99m, a still unique radionuclide within the nuclear medicine scenario because of its ideal nuclear properties and easy preparation of its radiopharmaceuticals that does not require a costly infrastructure and complex procedures. Scope of this review is to show that the arsenal of technetium-99m radiopharmaceuticals is already equipped with imaging agents that may complement and integrate the role played by analogous tracers developed for positron emission tomography (PET). These include, in particular, somatostatin (SST) and prostate-specific membrane antigen (PSMA) receptor targeting agents, and a number of peptide-derived radiopharmaceuticals. Additionally, these recent technological developments, combined with new myocardial perfusion tracers having more favorable biodistribution and pharmacokinetic properties as compared to current commercial agents, may also reinvigorate the prevailing position still hold by technetium-99m radiopharmaceuticals in nuclear cardiology.

PSMA-positive nodal recurrence in prostate cancer : Salvage radiotherapy is superior to salvage lymph node dissection in retrospective analysis

PURPOSE

This analysis compares salvage lymph node dissection (SLND) to salvage lymph node radiotherapy (SLNRT) of ⁶⁸Ga-PSMA PET-positive nodal recurrences after radical prostatectomy (RPE).

METHODS

A total of 67 SLNRT and 33 SLND consecutive patients with pelvic and/or para-aortic nodal recurrences after RPE were retrospectively analyzed. Biochemical recurrence-free survival rates (bRFS; PSA <0.2 ng/mL) were calculated according to Kaplan-Meier and survival curves were compared using the log rank test. For multivariable analysis, binary logistic regression analysis was performed (p < 0.05).

RESULTS

Median follow-up was 17 months (range, 6-53 months) in SLND patients and 31 months (range, 3-56 months) in SLNRT patients (p = 0.027). SLNRT patients had significantly more tumours of pT3 and pT4 category (82% vs. 67%; p = 0.006), pathologically involved lymph nodes (45% vs. 27%; p = 0.001) and positive surgical margins (54% vs. 12%; p = 0.001) at time of RPE than SLND patients. PSA persistence after RPE was significantly more frequently observed in the SLNRT cohort (73% vs. 27%; p = 0.001). There was no significant difference in the distribution of PET-positive lymph nodes. Median PSA before SLND was higher than before SLNRT (3.07 ng/ml vs. 1.3 ng/ml; p = 0.393). The 2‑year bRFS was significantly higher in the SLNRT vs. the SLND cohort (92% vs. 30%; p = 0.001) with lower rates of distant metastases (21% vs. 52%; p = 0.002) and secondary treatments (5% vs. 39%; p = 0.011) irrespective of ongoing androgen deprivation therapy at last contact. In multivariable analysis, SLNRT was significantly associated with prolonged bRFS (regression coefficient 1.436, hazard ratio 4.204, 95% CI 1.789-9.878; p = 0.001).

CONCLUSION

Based on this retrospective study SLNRT might be the preferred treatment option for patients with nodal recurrence after previous RPE.

Results from extended lymphadenectomies with [111In]PSMA-617 for intraoperative detection of PSMA-PET/CT-positive nodal metastatic prostate cancer

Purpose

Identification of suspicious PSMA-PET/CT-positive lymph node (LN) metastases (LNM) from prostate cancer (PCa) during lymphadenectomy (LA) is challenging. We evaluated an ¹¹¹In-labelled PSMA ligand (DKFZ-617, referred to as [¹¹¹In]PSMA-617) as a γ-emitting tracer for intraoperative γ-probe application for resected tissue samples in PCa patients. Forty-eight hours prior to LA, [¹¹¹In]PSMA-617 was administered intravenously in 23 patients with suspected LNM on PSMA-PET/CT (n = 21 with biochemical relapse, n = 2 at primary therapy). Resected tissue samples (LN, LNM and fibrofatty tissue) were measured ex situ by a γ-probe expressed as counts per second (CPS_norm). [¹¹¹In]PSMA-617 tissue sample uptake was measured by a germanium detector for verification and calculated as %IA_lbm (percent injected activity per kilogram lean body mass at time of surgery). Based on a clinical requirement for a specificity > 95%, thresholds for both ex situ measurements were chosen accordingly. Correlation of the results from PET/CT, γ-probe and germanium detector with histopathology was done.

Results

Eight hundred sixty-four LNs (197 LNM) were removed from 275 subregions in 23 patients, on average 8.6 ± 14.9 LNM per patient. One hundred four of 275 tissue samples showed cancer. Median γ-probe and germanium detector results were significantly different between tumour-affected (33.5 CPS_norm, 0.71 %IA_lbm) and tumour-free subregions (3.0 CPS_norm, 0.03 %IA_lbm) (each p value < 0.0001). For the chosen γ-probe cut-off (CPS_norm > 23) and germanium detector cut-off (%IA_lbm > 0.27), 64 and 74 true-positive and 158 true-negative samples for both measurements were identified. Thirty-nine and 30 false-negative and 6 and 5 false-positive tissue samples were identified by γ-probe and germanium detector measurements.

Conclusion

[¹¹¹In]PSMA-617 application for LA is feasible in terms of an intraoperative real-time measurement with a γ-probe for detection of tumour-affected tissue samples. γ-probe results can be confirmed by precise germanium detector measurements and were significantly different between tumour-affected and tumour-free samples.

Mapping Prostate Cancer Lesions Before and After Unsuccessful Salvage Lymph Node Dissection Using Repeat PSMA PET

The aim of this study was to analyze patterns of persistent versus recurrent or new PET lesions in a selected patient cohort with prostate-specific antigen (PSA) persistence after salvage lymph node dissection (SLND) and pre-procedure and post-procedure prostate-specific membrane antigen (PSMA) ligand PET. Methods: Sixteen patients were included in this multicenter study. The inclusion criteria were PSMA PET performed for biochemical recurrence before SLND (pre-SLND PET) and repeat PSMA PET performed for a persistently elevated PSA level (≥0.1 ng/mL) at least 6 wk after SLND (post-SLND PET). Image analysis was performed by 3 independent nuclear medicine physicians applying the molecular imaging TNM system PROMISE. Lesions were confirmed by histopathology, presence on correlative CT/MRI/bone scanning, or PSA response after focal therapy. Results: Post-SLND PET identified prostate cancer lesions in 88% (14/16) of patients with PSA persistence after SLND. Median PSA was 1.2 ng/mL (interquartile range, 0.6-2.8 ng/mL). Disease was confined to the pelvis in 56% of patients (9/16), and most of these men had common iliac (6/16, 38%) and internal iliac lymph node metastases (6/16, 38%). Extrapelvic disease was detected in 31% of patients (5/16). In pre- and post-SLND PET comparison, 10 of 16 had at least one lesion already detected at baseline (63% PET persistence), 4 of 16 had new lesions only (25% PET recurrence), and 2 had no disease on post-SLND PET. All validated regions (11 regions in 9 patients) were true-positive. Nine of 14 (64%) patients underwent repeat local therapies after SLND (7/14 radiotherapy, 2/14 surgery). Conclusion: SLND of pelvic nodal metastases was often not complete according to PSMA PET. About two thirds of patients had PET-positive nodal disease after SLND already seen on pre-SLND PSMA PET. Notably, about one quarter of patients had new lesions, not detected by presurgical PSMA PET.

Enhancing PSMA-uptake with androgen deprivation therapy - a new way to detect prostate cancer metastases?

Purpose:

⁶⁸Ga-PSMA PET/CT imaging is a promising modality for the staging of recurrent prostate cancer (PCa). Current evidence suggests limited diagnostic value of the ⁶⁸Ga-PSMA PET/CT in PSA-levels ≤0.3ng/mL. Experimental data have demonstrated an increase in PSMA-expression in PCa metastases by androgen deprivation in vitro. The aim of the current study was to investigate a possible enhancing effect of PSMA with low-dose androgen deprivation in patients with BCR and low PSA-levels.

Materials and Methods:

Five patients with PCa and BCR, following radical prostatectomy, underwent ⁶⁸Ga-PSMA PET/CT. A consecutive ⁶⁸Ga-PSMA PET/CT was performed 6 to 11 days after injection of 80mg of Degarelix (Firmagon^®). We recorded PSA and testosterone serum-levels and changes of PSMA-uptake in ⁶⁸Ga-PSMA PET/CT images. Results: Median PSA prior ⁶⁸Ga-PSMA PET/CT was 0.27ng/mL. All patients had a decrease in testosterone serum levels from median 2.95μg/l to 0.16μg/l following Degarelix injection. We observed an increase in the standardized uptake value (SUV) in PSMA-positive lymphogenous and osseous lesions in two patients following androgen deprivation. In another two patients, no PSMA positive signals were detected in either the first or the second scan.

Conclusion:

Our preliminary results of this feasibility assessment indicate a possible enhancing effect of PSMA-imaging induced by low-dose ADT. Despite several limitations and the small number of patients, this could be a new approach to improve staging by ⁶⁸Ga-PSMA PET/CT in PCa patients with BCR after primary therapy. Further prospective studies with larger number of patients are needed to validate our findings.

Recent advances in nuclear and hybrid detection modalities for image-guided surgery

Introduction: Radioguided surgery is an ever-evolving part of nuclear medicine. In fact, this nuclear medicine sub-discipline actively bridges non-invasive molecular imaging with surgical care. Next to relying on the availability of radio- and bimodal-tracers, the success of radioguided surgery is for a large part dependent on the imaging modalities and imaging concepts available for the surgical setting. With this review, we have aimed to provide a comprehensive update of the most recent advances in the field. Areas covered: We have made an attempt to cover all aspects of radioguided surgery: 1) the use of radioisotopes that emit γ, β⁺, and/or β^- radiation, 2) hardware developments ranging from probes to 2D cameras and even the use of advanced 3D interventional imaging solutions, and 3) multiplexing solutions such as dual-isotope detection or combined radionuclear and optical detection. Expert opinion: Technical refinements in the field of radioguided surgery should continue to focus on supporting its implementation in the increasingly complex minimally invasive surgical setting, e.g. by accommodating robot-assisted laparoscopic surgery. In addition, hybrid concepts that integrate the use of radioisotopes with other image-guided surgery modalities such as fluorescence or ultrasound are likely to expand in the future.

[Oligometastatic prostate cancer management]

OBJECTIVE

To review biology and management of oligometastatic prostate cancer.

MATERIAL AND METHODS

Relevant publications were identified through Medline (www. ncbi.nlm.nih.gov), Embase (www.embase.com) and the US National Library of Medicine (www.clinicaltrials.org) databases using the following keywords, alone or in association, «prostate cancer; metastasis; oligo-metastasis». Articles were selected according to methods, language of publication and relevance. After careful selection 99 publications were eligible for our review.

RESULTS

Oligometastatic prostate cancer is a new entity including prostate cancer with a limited number of metastasis. This particular state becomes more frequent with the imaging progresses especially with the common use of new PET imaging with Choline or PSMA. There is no consensus about a strict definition of oligometastatic prostate cancer, number and sites of metastasis vary widely in the literature. Moreover, oligometastatic state can be observed de novo at the time of prostate cancer diagnosis as well as in case of recurrence after a primary treatment. There is actually an important lack of evidence-based medicine and no guidelines regarding treatment can be found. In de novo oligo-metatastatic prostate cancer, treatment of the primary tumor in association with androgen deprivation therapy seems to increase survival in selected patients but this needs to be confirmed by ongoing prospective clinical trials. In recurrent prostate cancer, metastasis directed therapy with or without androgen deprivation therapy is now routinely performed but its impact needs also to be analyzed.

CONCLUSION

In absence of consensus or guidelines, management of prostate cancer should be an individualized, patient-based management taking into account primary tumor stage and grade, number and types of metastasis and patient characteristics.

Dual-time-point 64 Cu-PSMA-617-PET/CT in patients suffering from prostate cancer

Regardless of its high positron energy, ⁶⁸ Ga-labeled PSMA ligands have become standard of care in metabolic prostate cancer imaging. ⁶⁴ Cu, a radionuclide with a much longer half-life (12.7 h), is available for PSMA labeling allowing imaging much later than ⁶⁸ Ga. In this study, the diagnostic performance of ⁶⁴ Cu-labeled PSMA was compared between early and late scans. Sixteen men (median age: 70 y) with prostate cancer in different stages underwent ⁶⁴ Cu-PSMA-617-PET/CT 2 and 22 hours post tracer injection. Pathologic and physiologic uptakes were analyzed for both points of time. Pathologic tracer accumulations occurred in 12 patients. Five patients presented with pathologic uptake in 17 different lymph nodes, two patients showed pathologic bone uptake in nine lesions, and seven patients had pathologic PSMA uptake in eight prostatic lesions. Physiologic uptake of the renal parenchyma, urine bladder, and salivary glands decreased over time, while the physiologic uptake of liver and bowel increased. In the present study, ⁶⁴ Cu-PSMA-617-PET demonstrated to be feasible for imaging prostate cancer for both the primary tumor site and metastases. Later imaging showed no additional, clinically relevant benefit compared with the early scans. At least the investigated time points we chose did not vindicate the additional expenditure.

Performance of [68Ga] Ga-PSMA 11 PET for detecting prostate cancer in the lymph nodes before salvage lymph node dissection: a systematic review and meta-analysis

BACKGROUND

Salvage lymph node dissection (sLND) for nodal recurrence in prostate cancer (PCa) patients with biochemical recurrence (BCR) is still not recommended in current guidelines, because of the diagnostic inaccuracy of current conventional imaging. To assess the performance of [⁶⁸Ga] Ga-prostate-specific membrane antigen conjugate 11 positron emission tomography (PSMA-PET) in detecting PCa lymph node metastasis using pathologic confirmation through sLND.

METHODS

Literature search was conducted using the MEDLINE, SCOPUS, Web of Science, and Cochrane Library on November 11th, 2018 to identify the eligible studies. Studies were eligible if they investigated the diagnostic performance of PSMA-PET before sLND in PCa patients with BCR and reported the number of true positive, false positive, false negative, and true negative on a lesion-based and/or field-based analyses to compare with histopathologic findings in sLND specimens.

RESULTS

Fourteen studies published between 2015 and 2018 comprising 462 patients were selected in this systematic review and meta-analysis. The positive predictive value of PSMA-PET before sLND on a patient-based analysis ranged between 0.70 and 0.93. The pooled sensitivity using lesion-based and field-based analyses were 0.84 (95%CI: 0.61-0.95) and 0.82 (95%CI: 0.72-0.89), respectively. The pooled specificity using lesion-based and field-based analyses were 0.97 (95%CI: 0.95-0.99) and 0.95 (95%CI: 0.70-0.99), respectively. The diagnostic odds ratio using lesion-based and field-based analyses were 189 (95%CI: 39-920) and 82 (95%CI: 8-832), respectively.

CONCLUSIONS

PSMA-PET before sLND provided highly accurate performance with clinically relevant high positive and negative predictive values for detecting lymph node disease in patients with BCR after local treatment with curative intent for PCa. PSMA-PET can identify the patients who are likely to benefit from sLND and possibly direct to lesion or region-based dissection.

PSMA-Targeted Radiopharmaceuticals for Imaging and Therapy

As described in more detail in other contributions in this issue of Seminars in Nuclear Medicine, prostate-specific membrane antigen (PSMA) has become one of the most promising molecular targets in nuclear medicine. Due to its overexpression on prostate cancer cells in proportion to the stage and grade of tumour progression, especially in androgen-independent, advanced and metastatic disease, various tracers for the detection and treatment of prostate cancer by means of radioligand imaging, radioligand therapy or radioguided surgery have been developed and transferred to clinical applications. Even though monoclonal antibodies were investigated and introduced as first PSMA-targeted probes, the inherent advantage of fast tumour uptake and rapid excretion of small molecules has shifted the research focus during the last decade to low molecular weight inhibitors with high affinity to PSMA, such as [¹⁸F]FDCFPyL, [¹⁸F]PSMA-1007, [⁶⁸Ga]PSMA-HBED, [¹⁷⁷Lu]PSMA-617, [¹⁷⁷Lu]PSMA-I&T, [^99mTc]MIP-1404 or [^99mTc]PSMA I&S, to mention only a few. Due to the plethora of such PSMA probes described during the last years, this review aims to give an overview over the specific characteristics of those radiopharmaceuticals that have already found widespread clinical application. In addition, recently introduced concepts such as PSMA-tracers with increased plasma protein binding, are discussed.

Advances in prostate-specific membrane antigen PET of prostate cancer

PURPOSE OF REVIEW

In recent years, a large number of reports have been published on prostate-specific membrane antigen (PSMA)/PET in prostate cancer (PCa). This review highlights advances in PSMA PET in PCa during the past year.

RECENT FINDINGS

PSMA PET/computed tomography (CT) is useful in detection of biochemical recurrence, especially at low prostate-specific antigen (PSA) values. The detection rate of PSMA PET is influenced by PSA level. For primary PCa, PSMA PET/CT shows promise for tumour localization in the prostate, especially in combination with multiparametric MRI (mpMRI). For primary staging, PSMA PET/CT can be used in intermediate and high-risk PCa. Intraoperative PSMA radioligand guidance seems promising for detection of malignant lymph nodes. While the use of PSMA PET/MRI in primary localized disease is limited to high and intermediate-risk patients and localized staging, in the recurrence setting, PET/MRI can be particularly helpful when the lesions are subtle. PSMA PET/CT is superior to choline PET/CT and other conventional imaging modalities.

SUMMARY

Molecular imaging with PSMA PET continues to pave the way for personalized medicine in PCa.However, large prospective clinical studies are still needed to fully evaluate the role of PSMA PET/CT and PET/MRI in the clinical workflow of PCa.

Single Lesion on Prostate-specific Membrane Antigen-ligand Positron Emission Tomography and Low Prostate-specific Antigen Are Prognostic Factors for a Favorable Biochemical Response to Prostate-specific Membrane Antigen-targeted Radioguided Surgery in Recurrent Prostate Cancer

BACKGROUND

Prostate-specific membrane antigen (PSMA)-ligand positron emission tomography (PET) allows detection of metastatic prostate cancer (PC) lesions at low prostate-specific antigen (PSA) values. To facilitate their intraoperative detection during salvage surgery, we recently introduced PSMA-targeted radioguided surgery (RGS).

OBJECTIVE

To describe the outcome of a large cohort of patients treated with PSMA-targeted RGS and to establish prognostic factors.

DESIGN, SETTING, AND PARTICIPANTS

A total of 121 consecutive patients with recurrent PC as defined by PSMA-ligand PET (median PSA: 1.13ng/ml) underwent PSMA-targeted RGS.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The frequency of a complete biochemical response (cBR; PSA <0.2ng/ml) without additional treatment and the duration of biochemical recurrence-free survival (bRFS, time from PSMA-targeted RGS with PSA <0.2ng/ml without further treatment) were evaluated and correlated with preoperatively available clinical variables.

RESULTS AND LIMITATIONS

In almost all patients (120/121, 99%) metastatic tissue could be removed. A cBR was achieved in 77 patients (66%). The chance of cBR was highest in patients with both low preoperative PSA and a single lesion (38/45: 84%). Median bRFS was 6.4mo in the whole patient cohort and 19.8mo for patients with cBR. Significantly longer median bRFS was observed in patients with a low preoperative PSA value (p=0.004, hazard ratio 1.48, 95% confidence interval 1.13-1.93) and with a single lesion in preoperative PSMA-ligand PET (14.0 vs 2.5mo, p=0.002).

CONCLUSIONS

PSMA-targeted RGS leads to a remarkable interval of bRFS in a subset of patients. The frequency of cBR and the duration of bRFS were highest in patients with a low preoperative PSA value and a single lesion on PSMA-ligand PET.

PATIENT SUMMARY

Prostate-specific membrane antigen radioguided surgery delays disease progression in selected patients with recurrent prostate cancer after radical prostatectomy. Patients with a single lesion of recurrence and a low prostate-specific antigen value had the best outcome.

Performance and Impact of Prostate Specific Membrane Antigen-Based Diagnostics in the Management of Men with Biochemical Recurrence of Prostate Cancer and its Role in Salvage Lymph Node Dissection

Up to 50% of patients initially treated for prostate cancer in a curative intent experience biochemical recurrence, possibly requiring adjuvant treatment. However, salvage treatment decisions, such as lymph node dissection or radiation therapy, are typically based on prostate specific antigen (PSA) recurrence. Importantly, common imaging modalities (e.g., computed tomography [CT], magnetic resonance imaging, and bone scan) are limited and the detection of recurrent disease is particularly challenging if PSA is low. Prostate specific membrane antigen (PSMA) positron-emission tomography/computed tomography (PET/CT) is a novel and promising imaging modality which aims to overcome the incapability of early identification of distant and regional metastases. Within this review, we summarize the current evidence related to PSMA-PET/CT in prostate cancer men diagnosed with biochemical recurrence after local treatment with curative intent. We discuss detection rates of PSMA-PET/CT stratified by PSA-levels and its impact on clinical decision making. Furthermore, we compare different image-fusion techniques such as PSMA-PET vs. F-/C-Choline-PET scans vs. PSMA-single photon emission computed tomography/CT. Finally, we touch upon the contemporary role of radio-guided-PSMA salvage lymphadenectomy.