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.

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.

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.

A hybrid radioactive and fluorescence approach is more than the sum of its parts; outcome of a phase II randomized sentinel node trial in prostate cancer patients

OBJECTIVE

To determine the diagnostic accuracy of the hybrid tracer indocyanine green (ICG)-Technetium-99 m(99mTc)-nanocolloid compared to sequential tracers of 99mTc-nanocolloid and free-ICG in detecting tumor-positive lymph nodes (LN) during primary surgery in prostate cancer (PCa) patients.

INTRODUCTION

Image-guided surgery strategies can help visualize individual lymphatic drainage patterns and sentinel lymph nodes (SLNs) in PCa patients. For lymphatic mapping radioactive, fluorescent and hybrid tracers are being clinically exploited. In this prospective randomized phase II trial, we made a head-to-head comparison between ICG-99mTc-nanocolloid (hybrid group) and 99mTc-nanocolloid and subsequent free-ICG injection (sequential group).

METHODS

PCa patients with a  >5% risk of lymphatic involvement according to the 2012 Briganti nomogram and planned for prostatectomy were included and randomized (1:1) between ultrasound-guided intraprostatic tracer administration of ICG-99mTc-nanocolloid (n = 69) or 99mTc-nanocolloid (n = 69) 5 h before surgery. Preoperative lymphoscintigraphy and SPECT/CT were performed to define the locations of the SLNs. Additionally, all participants in the sequential group received an injection of free-ICG at time of surgery. Subsequently, all (S)LNs were dissected using fluorescence guidance followed by an extended pelvic lymph node dissection (ePLND). The primary outcome was the total number of surgically removed (S)LNs and tumor-positive (S)LNs.

RESULTS

The total number of surgically removed (S)LN packages was 701 and 733 in the hybrid and sequential groups, respectively (p = 0.727). The total number of fluorescent LNs retrieved was 310 and 665 nodes in the hybrid and sequential groups, respectively (p < 0.001). However, no statistically significant difference was observed in the corresponding number of tumor-positive nodes among the groups (44 vs. 33; p = 0.470). Consequently, the rate of tumor-positive fluorescent LNs was higher in the hybrid group (7.4%) compared to the sequential group (2.6%; p = 0.002), indicating an enhanced positive predictive value for the hybrid approach. There was no difference in complications within 90 days after surgery (p = 0.78).

CONCLUSIONS

The hybrid tracer ICG-99mTc-nanocolloid improved the positive predictive value for tumor-bearing LNs while minimizing the number of fluorescent nodes compared to the sequential tracer approach. Consequently, the hybrid tracer ICG-99mTc-nanocolloid enables the most reliable and minimal invasive method for LN staging in PCa patients.

The Effect of Salvage Radiotherapy on Survival, Functional Outcomes and Quality of Life in Men with Persistent PSA After Robot-assisted Radical Prostatectomy; Which Patient Benefits More?

OBJECTIVE

The aim of this study was (a) to evaluate the effect of salvage radiotherapy(sRT) on survival, functional outcomes and quality of life in men with persistent prostate-specific antigen(PSA>0.1ng/ml) after robot-assisted radical prostatectomy(RARP), and (b) to reveal subgroups which benefit more from sRT.

MATERIALS AND METHODS

Data of 3409 patients who underwent RARP were retrieved from a high-volume institute database and 313 patients with persistent PSA were included in the further analyses. Patients who received sRT and those who did not were compared after propensity score matching. Progression-free(PFS), metastasis-free(MFS), androgen deprivation therapy(ADT)-free, cancer-specific(CSS), and overall survival(OS), patient-reported outcomes were the endpoints. Multivariable Cox regression models were developed to reveal treatment effect sizes for subgroups.

RESULTS

Overall persistent PSA rate was 9.2%. Median follow-up time after RARP was 4.5 years (IQR: 2.7-7.9). sRT was associated with improved PFS (HR 0.29; p<0.001), ADT-free survival (HR 0.34; p<0.001), MFS (HR 0.39; p=0.001), CSS (HR 0.34; p=0.03), and OS (HR 0.24; p=0.001). Positive surgical margins (HR 0.26; p<0.001 for ADT-free survival), advanced pT (HR 0.24; p<0.001 for PFS) and pN (HR 0.15; p=0.001 for MFS) and lower Gleason score (HR 0.15; p=0.001 for PFS) were associated with marked survival benefits of sRT. Bowel symptoms were observed more frequently in sRT+ patients than sRT- patients (34.3% versus 19.2%, p=0.01). Early sRT (<6 months postoperatively) was associated with bothering incontinence (p<0.001) and bowel symptoms (p=0.03).

CONCLUSIONS

Persistent PSA after RP is still a common challenge in the robotic surgery era. sRT provides clear survival benefits for all endpoints, especially in unfavourable loco-regional factors but low Gleason score.

Implementation of radioguided surgery in prostate cancer

With the development of new imaging technologies and tracers, the applications of radioguided surgery for prostate cancer are growing rapidly. The current paper aims to give an overview of the recent advances of radioguided surgery in the management of prostate cancer. We performed a literature search to give an overview of the current status of radioguided surgery for prostate cancer. Three modalities of radioguided surgery, the sentinel node procedure, Cerenkov Luminescence / beta-radio-guided surgery and radio-guided salvage surgery in recurrent prostate cancer, were reviewed in detail. Radioguided surgery for prostate cancer has shown promising value in the treatment of primary diagnosed prostate cancer and recurrent loco-regional lymph node positive prostate cancer. Advances have been made into minimal invasive (robot-assisted) laparoscopic surgery. The sentinel node procedure for prostate cancer has been further developed and is currently performed with high diagnostic sensitivity. Cerenkov luminescence imaging is a feasible and encouraging technique for intraoperative margin assessment in prostate cancer. Radioguided surgery in recurrent prostate cancer has shown to be feasible, yielding high sensitivity and specificity for detecting small local recurrences and metastases. With the availability of different new tracers, the road has been paved towards clinically feasible radioguided surgery for prostate cancer. Novel technologies now being developed for minimal invasive surgery are speeding up clinical research. Currently, none of the radioguided surgery techniques mentioned have been accepted as standard of care.