Value of 68Ga-PSMA HBED-CC PET for the Assessment of Lymph Node Metastases in Prostate Cancer Patients with Biochemical Recurrence: Comparison with Histopathology After Salvage Lymphadenectomy

68Ga-PSMA-11 PET/CT in restaging castration-resistant nonmetastatic prostate cancer: detection rate, impact on patients' disease management and adequacy of impact

We aimed to evaluate the impact of prostate-specific membrane antigen ligand labelled with gallium-68 (PSMA-11) PET/CT in restaging patients with castration-resistant nonmetastatic prostate cancer (PCa). Thirty patients were included. At least one malignant focus was found in 27/30 patients (90%). The PSMA-11 PET/CT positivity rate in patients whose prostate-specific antigen serum level (PSA) was greater than 2 ng/ml was 100% (20/20), significantly superior to that of patients whose PSA was less than 2 ng/ml (7/10 = 70%). Six patients (20%) were categorized as oligometastatic (≤3 metastatic foci). Based on the 17 patients for whom a standard of truth was feasible, the overall sensitivity and specificity of PSMA-11 PET/CT in detecting residual disease in castration-resistant PCa patients were 87% and 100% respectively. PSMA-11 PET/CT impacted patients’ disease management in 70% of cases, 60% of case when PSA was less than 2 ng/ml. This management was considered as adequate in 91% of patients. PSMA-11 PET/CT appeared to be effective in restaging patients with castration-resistant nonmetastatic PCa. PSMA-11 PET/CT should be considered as a replacement for bone scans under these conditions.

Pre-test 68Ga-PSMA-ligand PET/CT positivity in early biochemical recurrent prostate cancer after radical prostatectomy-validation of a prediction model

OBJECTIVES

The aim of this study was the validation of a recently established comprehensive and compact prediction model for 68Ga-PSMA-11-ligand positron-emission tomography (PET) positivity with an independent subsequent patient series.

METHODS

A total of 292 consecutive patients with early biochemical recurrence after radical prostatectomy and PSA values between 0.2 and 1 ng/ml who underwent 68Ga-PSMA-11-ligand PET/computed tomography (CT) between January 2016 and June 2017 were retrospectively included. The cohort was divided into a very low PSA value (0.2-0.5 ng/ml, n = 151) and a low PSA value (> 0.5-1 ng/ml, n = 141) subgroup. First, pre-test positivity probabilities for each patient were calculated according to the previously published comprehensive prediction model using all clinical variables (PSA value, ISUP grade group, T- and N-stage, patient under androgen deprivation therapy (ADT), previous radiation therapy) and the compact model using just the most predictive factors PSA value, ADT, and grade group. Then, all 68Ga-PSMA-11-ligand PET/CTs were analysed by one experienced nuclear medicine physician, and the results were correlated to the calculated pre-test probabilities.

RESULTS

In the very low PSA value subgroup, mean pre-test probability for positive findings in 68Ga-PSMA-11-ligand PET/CT was 57% (95% CI 55-60%) according to the compact model and 59% (95% CI 56-61%) according to the comprehensive model. In the low PSA value subgroup, mean pre-test probability was 72% (95% CI 70-74%) in the compact model and 74% (95% CI 72-76%) in the comprehensive model. After image analysis, 59% (89/151) of the patients in the very low PSA value subgroup revealed positive imaging findings. Seventy-nine percent (112/141) of the patients in the low PSA value subgroup presented with positive findings in the 68Ga-PSMA-11-ligand PET/CT. The accuracy (AUC) of the prediction models was 0.71 (95% CI 0.65-0.78) for the compact model and 0.74 (95% CI 0.68-0.80) for the comprehensive model.

CONCLUSION

External validation of the recently proposed prediction models showed a high concordance of the calculated pre-test probabilities and actual 68Ga-PSMA-11-ligand PET/CT findings in the validation cohort confirming the prediction models' ability to determine the presence of a positive lesion at 68Ga-PSMA-11-ligand PET. However, the predictive accuracy of the nomogram itself is suboptimal and should be used with caution. Furthermore, the model's generalizability may be hampered due to the study design (in-house validation). Nevertheless, given the limited health resources and the costs of hybrid imaging techniques, prediction models might be a benefit in patient selection.

Simultaneous whole-body PET/MRI with integrated multiparametric MRI for primary staging of high-risk prostate cancer

PURPOSE

Whole-body positron emission tomography/magnetic resonance imaging (wbPET/MRI) is a promising diagnostic tool of recurrent prostate cancer (PC), but its role in primary staging of high-risk PC (hrPC) is not well defined. Thus, the aim was to compare the diagnostic accuracy for T-staging of PET-blinded reading (PBR) and PET/MRI.

METHODS

In this prospective study, hrPC patients scheduled to radical prostatectomy (RPx) with extended lymphadenectomy (eLND) were staged with wbPET/MRI and either ⁶⁸Ga-PSMA-11 or ¹¹C-choline including simultaneous multiparametric MRI (mpMRI). Images were assessed in two sessions, first as PBR (mpMRI and wbMRI) and second as wbPET/MRI. Prostate Imaging Reporting and Data System criteria (PIRADS v2) were used for T-staging. Results were correlated with the exact anatomical localization and extension as defined by histopathology. Diagnostic accuracy of cTNM stage according to PBR was compared to pathological pTNM stage as reference standard.

RESULTS

Thirty-four patients underwent wbPET/MRI of ⁶⁸Ga-PSMA-11 (n = 17) or ¹¹C-choline (n = 17). Twenty-four patients meeting the inclusion criteria of localized disease ± nodal disease based on imaging results underwent RPx and eLND, whereas ten patients were excluded from analysis due to metastatic disease. T-stage was best defined by mpMRI with underestimation of tumor lesion size by PET for both tracers. N-stage yielded a per patient sensitivity/specificity comparable to PBR.

CONCLUSION

MpMRI is the primary modality for T-staging in hrPC as PET underestimated T-stage in direct comparison to final pathology. In this selected study, cohort MRI shows no inferiority compared to wbPET/MRI considering N-staging.

18F-rhPSMA-7 PET for the Detection of Biochemical Recurrence of Prostate Cancer After Radical Prostatectomy

¹⁸F-labeled prostate-specific membrane antigen (PSMA) PET tracers are increasingly used in preference to ⁶⁸Ga-PSMA-11 for restaging biochemical recurrence (BCR) of prostate cancer. They are associated with longer half-lives, larger-scale production, and lower positron range than their ⁶⁸Ga-labeled counterparts. Here, we describe the efficacy of an ¹⁸F-labeled radiohybrid PSMA, rhPSMA-7, a novel theranostic PSMA-targeting agent for imaging BCR of prostate cancer. Methods: Datasets from 261 consecutive patients with noncastrate BCR after radical prostatectomy who underwent ¹⁸F-rhPSMA-7 PET/CT at our institution between June 2017 and March 2018 were reviewed retrospectively. All lesions suspected of being recurrent prostate cancer were recorded. The detection rate for sites of presumed recurrence was correlated with patients' prostate-specific antigen (PSA) level, primary Gleason score, and prior therapy (androgen deprivation therapy and external-beam radiation therapy). Results: The 261 patients had a median PSA level of 0.96 ng/mL (range, 0.01-400 ng/mL). The median injected activity of ¹⁸F-rhPSMA-7 was 336 MBq, with a median uptake time of 76 min. In total, 211 patients (81%) showed pathologic findings on ¹⁸F-rhPSMA-7 PET/CT. The detection rates were 71% (42/59), 86% (44/51), 86% (42/49), and 95% (76/80) at PSA levels of 0.2 to <0.5 ng/mL, 0.5 to <1 ng/mL, 1 to <2 ng/mL, and ≥2 ng/mL, respectively. In 32% patients (7/22) with a PSA of less than 0.2 ng/mL, suggestive lesions were present. ¹⁸F-rhPSMA-7 PET/CT revealed local recurrence in 43% of patients (113). Lymph node metastases were present in the pelvis in 42% of patients (110), in the retroperitoneum in 17% (45), and in a supradiaphragmatic location in 8.0% (21). Bone and visceral metastases were detected in 21% (54) and 3.8% (10), respectively. Detection efficacy was not influenced by prior external-beam radiation therapy (79.1% vs. 82.1%, P = 0.55), androgen deprivation therapy within the 6 mo preceding imaging (80.6% vs. 80.9%, P = 0.54), or primary Gleason score (77.9% for ≤7 vs. 82.6% for ≥8, P = 0.38). Conclusion: ¹⁸F-rhPSMA-7 PET/CT offers high detection rates in early BCR after radical prostatectomy, especially among patients with low PSA values.

Use of gallium-68 prostate-specific membrane antigen positron-emission tomography for detecting lymph node metastases in primary and recurrent prostate cancer and location of recurrence after radical prostatectomy: an overview of the current literature

Objectives

To review the literature to determine the sensitivity and specificity of gallium‐68 prostate‐specific membrane antigen (⁶⁸Ga‐PSMA) positron‐emission tomography (PET) for detecting pelvic lymph node metastases in patients with primary prostate cancer (PCa), and the positive predictive value in patients with biochemical recurrence (BCR) after initial curative treatment, and, in addition, to determine the detection rate and management impact of ⁶⁸Ga‐PSMA PET in patients with BCR after radical prostatectomy (RP).

Materials and Methods

We performed a comprehensive literature search. Search terms used in MEDLINE, EMBASE and Science Direct were ‘(PSMA, ⁶⁸Ga‐PSMA, ⁶⁸Gallium‐PSMA, Ga‐68‐PSMA or prostate‐specific membrane antigen)’ and ‘(histology, lymph node, staging, sensitivity, specificity, positive predictive value, recurrence, recurrent or detection)’. Relevant abstracts were reviewed and full‐text articles obtained where possible. References to and from obtained articles were searched to identify further relevant articles.

Results

Nine retrospective and two prospective studies described the sensitivity and specificity of ⁶⁸Ga‐PSMA PET for detecting pelvic lymph node metastases before initial treatment, which ranged from 33.3% to 100% and 80% to 100%, respectively. In eight retrospective studies, the positive predictive value of ⁶⁸Ga‐PSMA PET in patients with BCR before salvage lymph node dissection ranged from 70% to 100%. The detection rate of ⁶⁸Ga‐PSMA PET in patients with BCR after RP in the PSA subgroups <0.2 ng/mL, 0.2–0.49 ng/mL and 0.5 to <1.0 ng/mL ranged from 11.3% to 50.0%, 20.0% to 72.7% and 25.0% to 87.5%, respectively.

Conclusion

The review results showed that ⁶⁸Ga‐PSMA PET had a high specificity for the detection of pelvic lymph node metastases in primary PCa. Furthermore, ⁶⁸Ga‐PSMA PET had a very high positive predictive value in detecting lymph node metastases in patients with BCR. By contrast, sensitivity was only moderate; therefore, based on the currently available literature, ⁶⁸Ga‐PSMA PET cannot yet replace pelvic lymph node dissection to exclude lymph node metastases. In the salvage phase, ⁶⁸Ga‐PSMA PET had both a high detection rate and impact on radiotherapy planning in early BCR after RP.

Preparation and clinical translation of 99mTc-PSMA-11 for SPECT imaging of prostate cancer

This study explores the feasibility of radiolabeling the HBED-CC-PSMA (PSMA-11) ligand with Tc-99m for SPECT imaging of prostate cancer patients. ⁶⁸Ga-HBED-CC-PSMA (PSMA-11) is used clinically for PET/CT imaging of prostate cancer (PCa) patients. However, a PET/CT facility may not be affordable and/or accessible to remotely located health centers. Thus, economic considerations require development of a SPECT-based tracer to provide low cost effective health care to the entire global population. Hence, radiochemical parameters were varied and optimized to obtain the maximum radiochemical yield of ^99mTc-PSMA-11. ^99mTc-PSMA-11 could be prepared in 60 ± 5% radiochemical yield and >98% radiochemical purity with a specific activity of 15 ± 5 GBq μmol^-1. The radiotracer exhibited high stability in vitro in human serum after 24 h. A cell uptake of 15.2 ± 1.2% was observed for ^99mTc-PSMA-11 in PSMA-positive prostate carcinoma LNCaP cells. Rapid clearance from blood, liver, intestine, lungs and other major organs was observed during normal biodistribution studies. The radiotracer, ^99mTc-PSMA-11, exhibited physiological distribution in salivary and lacrimal glands similar to that of ⁶⁸Ga-PSMA-11 in mice and successfully identified primary tumors as well as metastatic lesions in human patients. This study thus highlights successful radiolabeling of HBED-CC-PSMA with Tc-99m and the potential of ^99mTc-PSMA-11 as a SPECT imaging agent for PCa.

Good clinical practice recommendations for the use of PET/CT in oncology

Positron emission tomography/computed tomography (PET/CT) is a nuclear medicine functional imaging technique with proven clinical value in oncology. PET/CT indications are continually evolving with fresh advances made through research. French practice on the use of PET in oncology was framed in recommendations based on Standards-Options-Recommendations methodology and coordinated by the French federation of Comprehensive Cancer Centres (FNLCC). The recommendations were originally issued in 2002 followed by an update in 2003, but since then, a huge number of scientific papers have been published and new tracers have been licenced for market release. The aim of this work is to bring the 2003 version recommendations up to date. For this purpose, a focus group was set up in collaboration with the French Society for Nuclear Medicine (SFMN) to work on developing good clinical practice recommendations. These good clinical practice recommendations have been awarded joint French National Heath Authority (HAS) and French Cancer Institute (INCa) label status-the stamp of methodological approval. The present document is the outcome of comprehensive literature review and rigorous appraisal by a panel of experts, organ specialists, clinical oncologists, surgeons and imaging specialists. These data were also used for the EANM referral guidelines.

Gallium-68 prostate-specific membrane antigen positron emission tomography/computed tomography compared with diagnostic computed tomography in relapsed prostate cancer

The aim of this study was to evaluate if prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) has a higher detection rate compared to standard contrast CT imaging for patients with a rising prostate-specific antigen (PSA) following definitive treatment (i.e., curative radical prostatectomy, radiotherapy, and brachytherapy) for prostate cancer in a private hospital setting. A retrospective single-site clinical audit was conducted on 150 PSMA PET/CT scans done for patients with a rising PSA after definitive treatment for prostate cancer. All studies were performed using I and T Ga-68 PSMA produced on a Scintomics radiopharmaceutical unit (Munich). All scans were performed on a GE 710 PET/CT scanner. All studies were compared to standard CT and other imaging. Of the 150 patients who had a ⁶⁸Gallium (Ga)-PSMA PET/CT for a rise in their PSA levels, 102/150 (68%) of patients had PSMA-avid scans compared to the conventional imaging group which had an overall detection rate of 42% (63/150). The rates of detection were 100%, 90%, 92%, 67%, and 25% at PSA levels of >10 μg/L, 5–10 μg/L, >1.5 μg/L, 0.5–1.5 μg/L, and <0.5 μg/L, respectively. PSMA PET/CT also solely picked up 39/102 (38%) of prostate cancer relapses compared to the conventional imaging group. In our study of 150 patients with biochemical recurrence of prostate cancer, ⁶⁸Ga-PSMA PET/CT demonstrated a superior detection rate (P < 0.05) compared to conventional imaging, including patients with low PSA levels (<0.5 μg/L).

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.

Accuracy of standard clinical 3T prostate MRI for pelvic lymph node staging: Comparison to 68Ga-PSMA PET-CT

The aim was to assess the performance of prostate 3T MRI for pelvic lymph node (LN) staging in prostate cancer (PCa), in comparison to ⁶⁸Gallium-prostate specific membrane antigen PET-CT (⁶⁸Ga-PSMA PET-CT) as reference standard for LN detection. 130 patients with PCa underwent non-contrast-enhanced multiparametric prostate 3T MRI and ⁶⁸Ga-PSMA-PET-CT within 180 days at our institution. Overall, 187 LN metastases (n = 43 patients) detected by ⁶⁸Ga-PSMA-PET-CT were characterized by calculating maximum standardized uptake value (SUVmax), area, diameter and anatomical location including iliac, obturator, presacral and inguinal region. MRI achieved an overall sensitivity, specificity, positive and negative predictive value of 81.6% (CI 71.1-88.9%), 98.6% (CI 97.6-99.2%), 73.5% (CI 52.1-87.6%) and 99.5% (CI 98.8-99.8%), respectively. On a region-based analysis, detection rates differed non-significantly (ps > 0.12) in the anatomical regions. On a size-dependent analysis, detection of LN > 10 mm did not differ significantly (ps > 0.09) from LN ≤ 10 mm. In comparison to single T1 sequence evaluation, additional use of the T2 weighted sequences did not improve the overall performance significantly (p > 0.05). 3T prostate MRI represented an accurate tool for the detection of LN compared to ⁶⁸Ga-PSMA-PET-CT. Especially for LN metastases smaller than 10 mm, MRI was less accurate compared to ⁶⁸Ga-PSMA-PET-CT.

Comparison between pelvic PSMA-PET/MR and whole-body PSMA-PET/CT for the initial evaluation of prostate cancer: a proof of concept study

OBJECTIVES

Despite the advantages of prostate-specific membrane antigen (PSMA)-PET/MR over PSMA-PET/CT, its relatively long scanning time and suboptimal PET attenuation correction necessitate careful assessment of the most appropriate setting for this type of study. We assessed lesion agreement between PSMA-PET/MR and PSMA-PET/CT in patients undergoing initial evaluation of prostate cancer.

METHODS

This was a prospective study of consecutive patients with histological biopsy-proven prostate cancer who underwent pelvic PSMA-PET/MR followed by whole-body PSMA-PET/CT. All conspicuous PSMA-avid foci were counted on PSMA-PET/CT and PSMA-PET/MR with CT or MR correlation. Analysis was performed for intra-prostatic lesions, capsular invasion, seminal vesicle involvement and lymph node and bone involvement. Incidental and significant findings seen on PSMA-PET/CT outside the PSMA-PET/MR field of view were also analysed. Agreements between PSMA-PET/CT and PSMA-PET/MR findings were performed using Cohen's kappa test.

RESULTS

Image analysis was performed on 140 patients (mean age, 67.3 ± 8.2 years). Agreement between PSMA PET/CT and PSMA-PET/MR was very good for intra-prostatic PSMA-avid foci (K = 0.85) and pelvic lymph nodes (K = 0.98), good for PSMA-avid bone metastases (K = 0.76) and fair for prostatic capsular invasion (K = 0.25) and seminal vesicle involvement (K = 0.31). Twelve patients (8.5%) had incidental findings and two patients (1.4%) had clinically significant findings.

CONCLUSION

Limited pelvic PSMA-PET/MR has very good agreement with PET/CT regarding PSMA-avid prostatic, regional lymph nodes and bone lesions, and is superior to PET/CT with regard to capsular invasion and seminal vesicle involvement.

KEY POINTS

• Limited pelvic PSMA-PET/MR is superior to whole-body PSMA-PET/CT in detecting extensions of localised disease, mainly due to the high soft tissue resolution of MR. • Limited pelvic PSMA-PET/MR may be useful for initial evaluation of histological biopsy-proven prostate cancer. • Further studies are warranted to evaluate limited pelvic PSMA-PET/MR for screening and active surveillance in selected populations.

Can the Injected Dose Be Reduced in 68Ga-PSMA-11 PET/CT While Maintaining High Image Quality for Lesion Detection?

Our purpose was to define a clinically useful lower limit of injected dose for ⁶⁸Ga-prostate-specific membrane antigen (PSMA)-11 PET/CT imaging of prostate cancer. Methods: ⁶⁸Ga-PSMA-11 PET/CT was performed on 11 patients. PET was acquired in list mode and reconstructed using a 3-min full acquisition, a 2-min acquisition, and a 1-min acquisition to generate images obtained with three thirds (standard dose), two thirds (low dose), and one third (very low dose) of the injected dose, respectively. Overall image quality (5-point scale) was assessed, and the detectability of PSMA-positive lesions was determined by 3 readers and compared with the reference standard. Results: Image quality declined with decreasing dose (mean score of 4.1 ± 0.4 for the standard dose, 3.4 ± 0.7 for the low dose, and 1.9 ± 0.4 for the very low dose; all P < 0.05). Readers 1, 2, and 3 correctly identified the lesions (n = 21) at a rate of 100%, 100%, and 95% with the standard dose; 95%, 81%, and 90% with the low dose; and 71%, 76%, and 59% with the very low dose, respectively. Conclusion: ⁶⁸Ga-PSMA-11 dose reduction is not feasible without a negative impact on image quality and lesion detectability.

[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.

Matched-Pair Comparison of 68Ga-PSMA-11 PET/CT and 18F-PSMA-1007 PET/CT: Frequency of Pitfalls and Detection Efficacy in Biochemical Recurrence After Radical Prostatectomy

¹⁸F-labeled prostate-specific membrane antigen (PSMA)-ligand PET has several principal advantages over ⁶⁸Ga-PSMA-11. The purpose of this retrospective study was to evaluate the frequency of non-tumor-related uptake and the detection efficacy comparing ⁶⁸Ga-PSMA-11 PET/CT and ¹⁸F-PSMA-1007 PET/CT in recurrent prostate cancer (PC) patients. Methods: The study included 102 patients with biochemically recurrent PC after radical prostatectomy undergoing ¹⁸F-PSMA-1007 PET/CT imaging. On the basis of various clinical variables, patients with corresponding ⁶⁸Ga-PSMA-11 PET/CT scans were matched. All PET/CT scans (n = 204) were reviewed by 1 nuclear medicine physician. First, all PET-positive lesions were noted. Then, lesions suspected of being recurrent PC were differentiated from lesions attributed to a benign origin on the basis of known pitfalls and information from CT. For each region, the SUV_max of the lesion with the highest PSMA-ligand uptake was noted. Detection rates were determined, and SUV_max was compared separately for ⁶⁸Ga-PSMA-11 and ¹⁸F-PSMA-1007. Results: In total, ¹⁸F-PSMA-1007 PET and ⁶⁸Ga-PSMA-11 PET revealed 369 and 178 PSMA-ligand-positive lesions, respectively. ¹⁸F-PSMA-1007 PET revealed approximately 5 times more lesions attributed to a benign origin than did ⁶⁸Ga-PSMA-11 PET (245 vs. 52 lesions, respectively). The benign lesions most frequently observed were ganglia, unspecific lymph node, and bone lesions, at a rate of 43%, 31%, and 24% for ¹⁸F-PSMA-1007 PET and 29%, 42%, and 27% for ⁶⁸Ga-PSMA-11 PET, respectively. The SUV_max of lesions attributed to a benign origin was significantly higher (P < 0.0001) for ¹⁸F-PSMA-1007 PET. Further, a similar number of lesions was attributed to recurrent PC (124/369 for ¹⁸F-PSMA-1007 PET and 126/178 for ⁶⁸Ga-PSMA-11 PET). Conclusion: The number of lesions with increased PSMA-ligand uptake attributed to a benign origin is considerably higher for ¹⁸F-PSMA-1007 PET than for ⁶⁸Ga-PSMA-11 PET. This finding indicates the need for sophisticated reader training emphasizing known pitfalls and reporting within the clinical context.

Feasibility of prostatectomy without prostate biopsy in the era of new imaging technology and minimally invasive techniques

BACKGROUND

Routinely, after receiving prostate specific antigen (PSA) testing and digital rectum examination, patients with suspected prostate cancer are required to undergo prostate biopsy. However, the ability of ultrasound-guided prostate biopsy to detect prostate cancer is limited. Nowadays, a variety of diagnostic methods and more sensitive diagnostic methods, such as multi-parameter prostate magnetic resonance imaging (mpMRI) and prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) can be applied clinically. Furthermore, laparoscopic/robot-assisted prostatectomy is also a safe and effective procedure for the treatment of benign prostatic hyperplasia. So maybe it is time to reconsider the necessary to perform prostate biopsy before radical prostatectomy.

AIM

To explore the feasibility of radical prostatectomy without prostate biopsy in the era of new imaging technology and minimally invasive techniques.

METHODS

From June 2014 to November 2018, 11 cases of laparoscopic radical prostatectomy without prostate biopsy were performed at the three tertiary medical centers involved in this study. All patients received prostate magnetic resonance imaging and prostate cancer was suspected, including six patients with positive ⁶⁸Ga-PSMA PET/CT results. Laparoscopic radical prostatectomy and pelvic lymph node dissection were performed for all patients.

RESULTS

All surgeries were accomplished successfully. The mean age was 69 ± 7.7 year, the mean body mass index was 24.7 ± 1.6 kg/m², the range of serum PSA was 4.3 to >1000 ng/mL, and the mean prostate volume was 40.9 ± 18.3 mL. The mean operative time was 96 ± 23.3 min, the mean estimated blood loss was 90 ± 90.9 mL, and the median duration of catheter placement was 14 d. The final pathology confirmed that all specimens were prostate cancer except one case of benign prostatic hyperplasia. No major complications occurred in 90 d postoperatively.

CONCLUSION

The current practice of mandating a prostatic biopsy before prostatectomy should be reconsidered in the era of new imaging technology and minimally invasive techniques. Radical prostatectomy could be carried out without the evidence of malignancy. Large-sample randomized controlled trials are definitely required to confirm the feasibility of this new concept.

Salvage lymphadenectomy in recurrent prostate cancer: is there evidence of real benefit?

PURPOSE

Nodal recurrent prostate cancer (PCa) after primary radical treatment represents a heterogeneous entity with many treatment options. In some cases, surgical removal of metastatic nodes seems to improve cancer control and delay systemic treatments. The objectives of this study were to analyze the available literature on salvage lymphadenectomy for the treatment of nodal recurrent PCa and to elucidate the real oncological benefit deriving from this procedure.

METHODS

A PubMed search was performed using the following terms: prostate cancer, metastatic, oligometastatic, salvage lymphadenectomy, salvage lymph node dissection, salvage lymph node excision, and cytoreductive surgery. We included in the study all papers on salvage lymphadenectomy in nodal recurrent PCa, with no temporal limits. In addition, several papers addressing cytoreductive surgery and the biology of oligometastatic disease, published in different medical and basic research journals, were included.

RESULTS

Salvage lymphadenectomy is still characterized by a lack of standardization in patient selection and surgical template. Its primary objectives are to prolong progression-free survival and to delay the need for systemic therapy. The improvements in preoperative imaging techniques in conjunction with the wide use of minimally invasive surgery have generated growing interest in this procedure.

CONCLUSION

Salvage lymphadenectomy is a promising treatment approach; however, its real oncological benefit is still far from proven. Prospective randomized trials need to be designed to improve understanding of this issue.

Consensus on molecular imaging and theranostics in prostate cancer

Rapid developments in imaging and treatment with radiopharmaceuticals targeting prostate cancer pose issues for the development of guidelines for their appropriate use. To tackle this problem, international experts representing medical oncologists, urologists, radiation oncologists, radiologists, and nuclear medicine specialists convened at the European Association of Nuclear Medicine Focus 1 meeting to deliver a balanced perspective on available data and clinical experience of imaging in prostate cancer, which had been supported by a systematic review of the literature and a modified Delphi process. Relevant conclusions included the following: diphosphonate bone scanning and contrast-enhanced CT are mentioned but rarely recommended for most patients in clinical guidelines; MRI (whole-body or multiparametric) and prostate cancer-targeted PET are frequently suggested, but the specific contexts in which these methods affect practice are not established; sodium fluoride-18 for PET-CT bone scanning is not widely advocated, whereas gallium-68 or fluorine-18 prostate-specific membrane antigen gain acceptance; and, palliative treatment with bone targeting radiopharmaceuticals (rhenium-186, samarium-153, or strontium-89) have largely been replaced by radium-223 on the basis of the survival benefit that was reported in prospective trials, and by other systemic therapies with proven survival benefits. Although the advances in MRI and PET-CT have improved the accuracy of imaging, the effects of these new methods on clinical outcomes remains to be established. Improved communication between imagers and clinicians and more multidisciplinary input in clinical trial design are essential to encourage imaging insights into clinical decision making.

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.

Comparing the Staging/Restaging Performance of 68Ga-Labeled Prostate-Specific Membrane Antigen and 18F-Choline PET/CT in Prostate Cancer: A Systematic Review and Meta-analysis

PURPOSE

PET/CT using prostate-specific membrane antigen (PSMA) and choline radiotracers is widely used for diagnosis of prostate cancer. However, the roles of and differences in diagnostic performance between these 2 radiotracers for prostate cancer are unclear. The aim of this study was to compare the staging and restaging performance of Ga-labeled PSMA and F-choline PET/CT imaging in prostate cancer.

METHODS

A comprehensive search was performed in PubMed for studies reporting the staging performance of Ga-PSMA and F-choline PET/CT in prostate cancer from the inception of the database to October 1, 2018, according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. Thirty-five studies were included in this systematic review and meta-analysis. Pooled estimates of patient- and lesion-based sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) for Ga-PSMA and F-choline PET/CT were calculated alongside 95% confidence intervals. Summary receiver operating characteristic curves were plotted, and the area under the summary receiver operating characteristic curve (AUC) was determined alongside the Q* index.

RESULTS

The patient-based overall pooled sensitivity, specificity, PLR, NLR, DOR, and AUC of Ga-PSMA PET/CT for staging in prostate cancer (13 studies) were 0.92, 0.94, 7.91, 0.14, 79.04, and 0.96, respectively, whereas those of F-choline PET/CT (16 studies) were 0.93, 0.83, 4.98, 0.10, 68.27, and 0.95. The lesion-based overall pooled sensitivity, specificity, PLR, NLR, DOR, and AUC of Ga-PSMA PET/CT for staging in prostate cancer (9 studies) were 0.83, 0.95, 23.30, 0.17, 153.58, and 0.94, respectively, and those of F-choline PET/CT (4 studies) were 0.81, 0.92, 8.59, 0.20, 44.82, and 0.98. In both patient- and lesion-based imaging, there was no statistically significant difference in the abilities of detecting or excluding prostate cancer between Ga-PSMA PET/CT and F-choline PET/CT.

CONCLUSIONS

For staging and restaging performance in patients with prostate cancer, there was no significant difference between Ga-PSMA PET/CT and F-choline PET/CT. Ga-PSMA PET/CT and F-choline PET/CT have demonstrated high diagnostic performance for accurate staging and restaging in patients with prostate cancer, and thus both should be considered for staging in this disease.

[PSA increase after definitive treatment]

Following definitive treatment with curative intent a subset of patients with prostate cancer experience biochemical recurrence. In these patients clinical parameters are mostly used to decide if a local or systemic disease recurrence is present. While salvage radiation treatment is advocated for local recurrence after radical prostatectomy, no standard recommendations exist in cases of local recurrence after primary radiation therapy although salvage prostatectomy may be considered. Imaging procedures have traditionally not routinely been recommended for the onset of prostate-specific antigen (PSA) relapse; however, prostate-specific membrane antigen (PSMA) positron emission tomography (PET) computed tomography (CT) exhibits high detection rates even at low PSA values. Thus, the current German guidelines state that PSMA PET/CT can be considered if this could result in a decisive change in further treatment management. Currently, a positive influence on oncological long-term outcome, however, has not yet been proven.

Single-Center Prospective Evaluation of 68Ga-PSMA-11 PET in Biochemical Recurrence of Prostate Cancer

OBJECTIVE. The purpose of this study was to determine the diagnostic accuracy of ⁶⁸Ga-labeled prostate-specific membrane antigen 11 (PSMA-11) PET for disease detection in patients with prostate cancer who have biochemically recurrent disease after radiation therapy or prostatectomy. SUBJECTS AND METHODS. One hundred fifty patients underwent ⁶⁸Ga-PSMA-11 PET/CT or PET/MRI, and the images were interpreted by two blinded board-certified radiologists. Each reader evaluated for the presence or absence of PSMA-positive disease within the prostate bed, pelvic lymph nodes, bones, and soft tissues (extrapelvic lymph nodes and visceral structures). The presence or absence of disease was confirmed by histopathologic analysis if available. For patients who did not have pathologic analysis, a composite of imaging and clinical follow-up was used as the reference standard. RESULTS. The median prostate-specific antigen level was 2.1 ng/mL. Forty-three patients had pathologic correlation, and for 29 patients a composite of imaging and follow-up was used to determine the presence or absence of disease. With substantial to almost perfect interreader reliability by region (κ = 0.78-0.87), ⁶⁸Ga-PSMA-11 PET had high sensitivity per region (up to 100%) and per patient (up to 89.8%). It also had high positive predictive value per region (up to 100%) and per patient (up to 91.5%). Sensitivity was highest for bone metastases and lowest for soft-tissue metastases. Positive predictive value was highest for bone metastases and lowest for prostate bed recurrence. CONCLUSION. Gallium-68-labeled PSMA-11 PET is sensitive for prostate cancer metastases in patients with biochemically recurrent prostate cancer. It has high positive predictive value and substantial to almost perfect interrater reliability.

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.

Diagnostic Performance of 68Gallium Labelled Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography and Magnetic Resonance Imaging for Staging the Prostate Cancer with Intermediate or High Risk Prior to Radical Prostatectomy: A Systematic Review and Meta-analysis

Purpose

To compare the diagnostic efficiency of ⁶⁸Gallium labelled prostate-specific membrane antigen positron emission tomography (⁶⁸Ga-PSMA PET) and magnetic resonance imaging (MRI) for staging the lymph node metastases (LNMs) in the prostate cancer.

Materials and Methods

A broad search of scientific databases including PubMed, EMBASE, Web of Science, Cochrane Database, and Chinese Biomedicine Literature Database (updated prior to November 1st, 2018) was conducted systematically by two reviewers. In this paper, we evaluated the methodological quality of each included article independently and performed a systematic review and meta-analysis to reveal the summary of the diagnostic performance of ⁶⁸Ga-PSMA PET and MRI in properly identifying LNMs of intermediate- and/or high-risk prostate cancer.

Results

Thirteen eligible articles comprising 1,597 patients were included. For LNMs detection, the pooled sensitivity and specificity of ⁶⁸Ga-PSMA PET were 0.65 (95% confidence interval [CI]: 0.49–0.79) and 0.94 (95% CI: 0.88–0.97), respectively, while the corresponding values of MRI were 0.41 (95% CI: 0.26–0.57) and 0.92 (95% CI: 0.86–0.95). The area under the symmetric receiver-operating characteristic (SROC) curve for ⁶⁸Ga-PSMA PET and MRI were 0.92 and 0.83, respectively.

Conclusions

In intermediate- or high-risk pre-treatment prostate cancer, ⁶⁸Ga-PSMA PET had a higher sensitivity and a slightly different specificity in probing the LNMs when comparing with MRI. Moreover, the area under the SROC curve indicated that ⁶⁸Ga-PSMA PET was a more effective weapon for predicting the LNMs prior to radical surgery.

68Ga-PSMA PET/CT in Patients with Rising Prostatic-Specific Antigen After Definitive Treatment of Prostate Cancer: Detection Efficacy and Diagnostic accuracy

RATIONALE AND OBJECTIVES

⁶⁸Ga-prostate-specific membrane antigen-11 (⁶⁸Ga-PSMA-11) is a recently developed positron emission tomography (PET) tracer that can detect prostate cancer (PC) relapses and metastases with high contrast resolution. The aim of this study was to assess the detection efficacy and diagnostic accuracy of ⁶⁸Ga-PSMA PET/CT image in patients with rising prostatic-specific antigen (PSA) after treatment of PC.

MATERIALS AND METHODS

The present prospective study included 188 patients who exhibited rising of PSA level on a routine follow-up examination after definitive treatment of PC. All patients underwent a ⁶⁸Ga-PSMA PET/CT examination. For each patient, we determined the disease stage, the Gleason score, and the maximum standardized uptake value of the local recurrence and extraprostatic metastases. The detection efficacy and diagnostic accuracy of ⁶⁸Ga-PSMA PET/CT were established by histopathology and clinical and imaging follow-up as the reference standards.

RESULTS

⁶⁸Ga-PSMA PET/CT detected tumour relapse in 165 patients (35 patients had local recurrence, 106 patients had extraprostatic metastases, and 24 patients had combined lesions). The sensitivity, specificity, and accuracy values of ⁶⁸Ga-PSMA PET/CT examination in the detection of PC recurrence were 98.8%, 100%, and 98.8%, respectively. ⁶⁸Ga-PSMA PET/CT revealed an overall detection rate of 87.8% (165/188) in patients with rising PSA (median of 2.2 ng/mL, and range of 0.01-70 ng/mL).

CONCLUSION

⁶⁸Ga-PSMA PET/CT is a valuable tool for the detection of PC local recurrence or extraprostatic metastases following rising PSA levels after primary definitive therapy and should be incorporated during routine work-up.

New Targets for PET Molecular Imaging of Prostate Cancer

Prostate cancer (PCa) is the most common cancer in men worldwide, but it exhibits a highly variable biological behavior ranging from indolent to highly aggressive disease. The standard conventional imaging for staging PCa consists of CT, MRI, and bone scans, but this imaging has suboptimal accuracy for extraprostatic tumor detection, particularly in the scenario of early biochemical relapse when the prostate-specific antigen levels are still low indicating a low volume of recurrent disease. This gap between known disease (as indicated by a rising prostate-specific antigen) and the failure to detect it on conventional imaging, has led to the development of novel imaging probes most of which have positron emitting radioactive tags. In the last decade, multiple PET probes have demonstrated promising performance in detecting sites of recurrence and extent of disease in patients with PCa. The landscape of available PET radiotracers is changing rapidly and includes radiolabeled choline, anti1-amino-3-¹⁸F-fluorocyclobutane-1-carboxylic acid (¹⁸F-fluciclovine), bombesin, dihydrotestosterone, and prostate-specific membrane antigen (PSMA) ligands, among others. Of these, radiolabeled PSMA-PET agents have shown the most encouraging results in terms of sensitivity and are likely to become universally available for imaging PCa within a few years Other PET radiotracers such as bombesin-based radiotracers and antagonist of gastrin releasing-peptide receptor (RM2) are emerging as possible alternatives for PCa imaging. This review article discusses the current and near-future of PET molecular imaging probes.

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.

Detection Rate of 18F-Choline PET/CT and 68Ga-PSMA-HBED-CC PET/CT for Prostate Cancer Lymph Node Metastases with Direct Link from PET to Histopathology: Dependence on the Size of Tumor Deposits in Lymph Nodes

Accurate detection of prostate cancer lymph node metastases (LNM) through PET/CT before lymphadenectomy is crucial for successful therapy. PET/CT with choline derivatives used to be the standard tool for imaging metastases, whereas ⁶⁸Ga-PSMA (prostate-specific membrane antigen) PET/CT was introduced recently. Both PET techniques were investigated with respect to what extent the detection rate of LNM depends on the size of tumor deposits (TDs) within LNM. Methods: Documenting the switch from the use of ¹⁸F-choline to ⁶⁸Ga-PSMA in 2014, we used 2 patient cohorts undergoing a template lymphadenectomy because of a PET/CT indicating LNM. Forty-four and 40 patients underwent PET/CT with ¹⁸F-choline or ⁶⁸Ga-PSMA ligand, respectively. In total, 226 LNM (125 ¹⁸F-choline, 101 ⁶⁸Ga-PSMA) originated from 73 salvage lymphadenectomies at biochemical recurrence and from 11 primary lymphadenectomies at radical prostatectomy. LNM eligible for direct correlation of PET/CT to histopathology were identified from lymphadenectomies conducted in small anatomic subregions, with 1 LNM (condition 1) or 1-2 LNM (condition 2). Longitudinal and short diameters of TD within LNM were determined by histopathology, allowing linking of the size of TD in LNM to the detection threshold of PET/CT. Diameters associated with a detection rate of 50% and 90% (d_50%, d_90%) were calculated on the basis of logistic growth curve models fitted. Results: Gleason score, number of removed LNs, and subregions for lymphadenectomy per patient did not differ significantly between the ¹⁸F-choline and ⁶⁸Ga-PSMA groups. The median prostate-specific antigen level at imaging and number of LNM per patient were significantly higher in the ¹⁸F-choline group (3.4 ng/mL, n = 34) than in the ⁶⁸Ga-PSMA group (2.2 ng/mL, n = 28; both P < 0.05). Longitudinal and short diameters of TD in LNM to reach d_90% were 11.2 and 7.4 mm, respectively, for ¹⁸F-choline PET/CT and 6.3 and 4.9 mm, respectively, for ⁶⁸Ga-PSMA PET/CT. Corresponding diameters to reach d_50% were 5.5 and 3.3 mm, respectively, for ¹⁸F-choline PET/CT and 3.7 and 2.3 mm, respectively, for ⁶⁸Ga-PSMA PET/CT. Detection rates were significantly higher under ⁶⁸Ga-PSMA (P = 0.005 and 0.04 for longitudinal and short diameter). Conclusion: ⁶⁸Ga-PSMA PET/CT is superior to ¹⁸F-choline PET/CT in the detection of LNM. Whether those results will lead to an improved patient outcome after ⁶⁸Ga-PSMA PET-guided therapy needs to be investigated by further studies.

Radiation dosimetry of [68Ga]PSMA-11 in low-risk prostate cancer patients

BACKGROUND

68Ga-labeled Glu-NH-CO-NH-Lys(Ahx)-HBED-CC ([68Ga]PSMA-11) has been increasingly used to image prostate cancer using positron emission tomography (PET)/computed tomography (CT) both during diagnosis and treatment planning. It has been shown to be of clinical value for patients both in the primary and secondary stages of prostate cancer. The aim of this study was to determine the effective dose and organ doses from injection of [68Ga]PSMA-11 in a cohort of low-risk prostate cancer patients.

METHODS

Six low-risk prostate cancer patients were injected with 133-178 MBq [68Ga]PSMA-11 and examined with four PET/CT acquisitions from injection to 255 min post-injection. Urine was collected up to 4 h post-injection, and venous blood samples were drawn at 45 min, 85 min, 175 min, and 245 min post-injection. Kidneys, liver, lungs, spleen, salivary and lacrimal glands, and total body where delineated, and cumulated activities and absorbed organ doses calculated. The software IDAC-Dose 2.1 was used to calculate absorbed organ doses according to the International Commission on Radiological Protection (ICRP) publication 107 using specific absorbed fractions published in ICRP 133 and effective dose according to ICRP Publication 103. We also estimated the absorbed dose to the eye lenses using Monte Carlo methods.

RESULTS

[68Ga]PSMA-11 was rapidly cleared from the blood and accumulated preferentially in the kidneys and the liver. The substance has a biological half-life in blood of 6.5 min (91%) and 4.4 h (9%). The effective dose was calculated to 0.022 mSv/MBq. The kidneys received approximately 40 mGy after an injection with 160 MBq [68Ga]PSMA-11 while the lacrimal glands obtained an absorbed dose of 0.12 mGy per administered MBq. Regarding the eye lenses, the absorbed dose was low (0.0051 mGy/MBq).

CONCLUSION

The effective dose for [68Ga]PSMA-11 is 0.022 mSv/MBq, where the kidneys and lacrimal glands receiving the highest organ dose.

Randomized prospective phase III trial of 68Ga-PSMA-11 PET/CT molecular imaging for prostate cancer salvage radiotherapy planning [PSMA-SRT]

BACKGROUND

Salvage radiotherapy (SRT) for prostate cancer (PCa) recurrence after prostatectomy offers long-term biochemical control in about 50-60% of patients. SRT is commonly initiated in patients with serum PSA levels < 1 ng/mL, a threshold at which standard-of-care imaging is insensitive for detecting recurrence. As such, SRT target volumes are usually drawn in the absence of radiographically visible disease. 68Ga-PSMA-11 (PSMA) PET/CT molecular imaging is highly sensitive and may offer anatomic localization of PCa biochemical recurrence. However, it is unclear if incorporation of PSMA PET/CT imaging into the planning of SRT could improve its likelihood of success. The purpose of this trial is to evaluate the success rate of SRT for recurrence of PCa after prostatectomy with and without planning based on PSMA PET/CT.

METHODS

We will randomize 193 patients to proceed with standard SRT (control arm 1, n = 90) or undergo a PSMA PET/CT scan (free of charge for patients) prior to SRT planning (investigational arm 2, n = 103). The primary endpoint is the success rate of SRT measured as biochemical progression-free survival (BPFS) after initiation of SRT. Biochemical progression is defined by PSA ≥ 0.2 ng/mL and rising. The randomization ratio of 1:1.13 is based on the assumption that approximately 13% of subjects randomized to Arm 2 will not be treated with SRT because of PSMA-positive extra-pelvic metastases. These patients will not be included in the primary endpoint analysis but will still be followed. The choice of treating the prostate bed alone vs prostate bed and pelvic lymph nodes, with or without androgen deprivation therapy (ADT), is selected by the treating radiation oncologist. The radiation oncologist may change the radiation plan depending on the findings of the PSMA PET/CT scan. Any other imaging is allowed for SRT planning in both arms if done per routine care. Patients will be followed until either one of the following conditions occur: 5 years after the date of initiation of randomization, biochemical progression, diagnosis of metastatic disease, initiation of any additional salvage therapy, death.

DISCUSSION

This is the first randomized phase 3 prospective trial designed to determine whether PSMA PET/CT molecular imaging can improve outcomes in patients with PCa early BCR following radical prostatectomy.

ACRONYM

PSMA-SRT Phase 3 trial.

CLINICAL TRIAL REGISTRATION

■ IND#130649 ◦ Submission: 04.26.2016 ◦ Safe-to-proceed letter issued by FDA: 05.25.2016 ■ UCLA IRB #18-000484, ■ First submission: 3.27.2018 ■ Date of approval: 5.31.2018 ■ UCLA JCCC Short Title NUC MED 18-000484 ■ NCI Trial Identifier NCI-2018-01518 ■ ClinicalTrials.gov Identifier NCT03582774 ■ First Submitted: 06.19.2018 ■ First Submitted that Met QC Criteria: 06.27.2018 ■ First Posted: 07.11.2018 ■ Last Update Submitted that Met QC Criteria: 07.17.2018 ■ Last Update Posted: 07.19.2018 TRIAL STATUS: Current Trial Status Active as of 08/13/2018 Trial Start Date 09/01/2018-Actual Primary Completion Date 09/01/2023-Anticipated Trial Completion Date 09/01/2024-Anticipated.

Comparison of 68 Ga-PSMA ligand PET/CT versus conventional cross-sectional imaging for target volume delineation for metastasis-directed radiotherapy for metachronous lymph node metastases from prostate cancer

PURPOSE

To assess the differences in the target volume (TV) delineation of metachronous lymph node metastases between ⁶⁸ Ga-PSMA ligand PET/CT and conventional imaging in a comparative retrospective contouring study.

PATIENTS AND METHODS

Twenty-five patients with biochemical prostate cancer recurrence after primary prostatectomy underwent ⁶⁸ Ga-PSMA ligand PET/CT in addition to conventional imaging techniques such as CT and/or MR imaging for restaging. All patients were diagnosed with at least one lymph node metastasis. TVs were manually delineated in two different ways: (a) based on conventional imaging (CT/MRI) and (b) based on conventional imaging (CT/MRI) plus ⁶⁸ Ga-PSMA ligand PET/CT. The size of TVs, overlap rates, and subjective assessment of the difficulty of TV delineation reported by the radiation oncologist (easy/moderate/difficult) were compared.

RESULTS

With the additional information from PSMA ligand PET, 47 lymph node metastases were identified and included in the gross tumor volume (GTV). The median clinical target volume (CTV) of non-PET-based TV delineation was statistically larger than the CTV based on PET imaging (134.8 ml [range 6.9-565.2] versus 44.9 ml [range 4.9-481.3; p = 0.001]). The CTV based on CT/MRI enclosed only 81.3% (39/48) of PET-positive lymph nodes. The CT/MRI-based CTV did not enclose all PET-positive lymph nodes in 24% (6/25) of patients. In 12% (3/25) of patients, all PET-positive lymph nodes were outside of the CT/MRI-based CTV. The median overlap rates (TV_PET/TV_CT/MRI × 100) were 45.7% (range 0-96.9) for the GTV and 71.7% (range 9.8-98.2) for the CTV. The assessment of difficulty of contouring revealed that contouring with the additional imaging information of the PET was categorized as easy/moderate in 92% (23/25) and as difficult in 8% (2/25) of the cases, whereas contouring based on CT/MRI without PET was categorized as difficult in 56% (14/25) and as easy/moderate in 44% of the cases (11/25; p = 0.003).

CONCLUSION

⁶⁸ Ga-PSMA ligand PET/CT is superior to conventional cross-sectional imaging for the delineation of lymph node metastases from prostate cancer. PET-based TV delineation allows for smaller target volumes and should be considered the standard for irradiation of metachronous lymph node metastases in recurrent prostate cancer. Conventional imaging is not sufficiently sensitive for radio-oncological treatment concepts in oligometastatic prostate cancer.

68Gallium-labelled PSMA-PET/CT as a diagnostic and clinical decision-making tool in Asian prostate cancer patients following prostatectomy

Objective

Prostate cancers (PCa) in Asian individuals are molecularly distinct from those found in their Caucasian counterparts. There is no risk stratification tool for Asian men with rapid biochemical recurrence (BCR) following radical prostatectomy (RadP). This study aims to assess the detection rate of ⁶⁸Ga-prostate-specific membrane antigen-positron emission tomography/computed tomography (PSMA-PET/CT) for diagnosis of clinical recurrence and as a treatment decision making tool in Asian patients with BCR post-RadP.

Methods

⁶⁸Ga PSMA-PET and CT body with/without bone scan [conventional workup (CWU)] were performed in 55 Asian patients with BCR within 36 months post-RadP. Two blinded reviewers assessed the images. Detection rates of ⁶⁸Ga PSMA-PET/CT were evaluated, and impact on management was reviewed by comparison with CWU.

Results

Median time to BCR post-RadP was 8.1 months. Detection rate for ⁶⁸Ga PSMA-PET/CT was 80% (44/55). A positive scan was significantly associated with increasing prostate-specific antigen (PSA) level [odds ratio (OR) = 1.13 (95% CI 1.05–1.30), P = 0.017], but not with higher Gleason grade or shorter PSA doubling time. Compared to CWU, ⁶⁸Ga PSMA-PET/CT detected an additional 106 lesions in 33/44 patients with a positive scan, resulting in a change in management in 25/44 (56.8%) patients: 10 to hormonal therapy (HT) and whole pelvis radiotherapy (RT) in addition to bed RT, and 15 to palliative HT alone.

Conclusions

In the present report, we demonstrated the diagnostic and treatment decision utility of ⁶⁸Ga PSMA-PET/CT in Asian men with rapid BCR. Detection of small volume nodal and systemic recurrences at low PSA levels (< 1.0 ng/mL) highlights the role of the tool in assigning patients to treatment intensification with HT-RT or palliative HT in polymetastatic disease.