Evaluating Biochemically Recurrent Prostate Cancer: Histologic Validation of 18F-DCFPyL PET/CT with Comparison to Multiparametric MRI

Diagnostic Accuracy of 18F-Prostate Specific Membrane Antigen (PSMA) PET/CT Radiotracers in Staging and Restaging of Patients With High-Risk Prostate Cancer or Biochemical Recurrence: An Overview of Reviews

The aim of this overview was to consolidate existing evidence syntheses and provide a comprehensive overview of the evidence for 18F-prostate specific membrane antigen (PSMA) PET/CT in the staging of high-risk prostate cancer and restaging after biochemical recurrence. An overview of reviews was performed and reported in line with the preferred reporting items for overview of reviews (PRIOR) statement and synthesis without meta-analysis (SWiM) reporting guidelines. A comprehensive database and grey literature search were conducted up to July 18, 2023. Systematic reviews were assessed using the risk of bias in systematic reviews (ROBIS) tool. The certainty of the evidence was assessed using grading of recommendations, assessment, development and evaluations (GRADE). 11 systematic reviews were identified; 10 were at high or unclear risk of bias. Evidence reported on a per-patient, per-lymph node, and per-lesion basis for sensitivity, specificity and overall accuracy was identified. There was a lack of data on dose, adverse events and evidence directly comparing 18F-PSMA PET/CT to other imaging modalities. Evidence with moderate to very low certainty indicated high sensitivity, specificity and accuracy of 18F-PSMA PET/CT in patients with high-risk prostate cancer and biochemical recurrence. There was considerably lower certainty evidence and greater variability in effect estimates for outcomes for the combined intermediate/high-risk cohort. While evidence gaps remain for some outcomes, and most systematic reviews were at high or unclear risk of bias, the current evidence base is broadly supportive of 18F-PSMA PET/CT imaging in the staging and restaging of patients with high-risk prostate cancer and biochemical recurrence.

Current Applications of PET/MR: Part II: Clinical Applications II

Due to the major improvements in the hardware and image reconstruction algorithms, positron emission tomography/magnetic resonance imaging (PET/MR) is now a reliable state-of-the-art hybrid modality in medical practice. Currently, it can provide a broad range of advantages in preclinical and clinical imaging compared to single-modality imaging. In the second part of this review, we discussed the further clinical applications of PET/MR. In the chest, PET/MR has particular potential in the oncology setting, especially when utilizing ultrashort/zero echo time MR sequences. Furthermore, cardiac PET/MR can provide reliable information in evaluating myocardial inflammation, cardiac amyloidosis, myocardial perfusion, myocardial viability, atherosclerotic plaque, and cardiac masses. In gastrointestinal and hepato-pancreato-biliary malignancies, PET/MR is able to precisely detect metastases to the liver, being superior over the other imaging modalities. In genitourinary and gynaecology applications, PET/MR is a comprehensive diagnostic method, especially in prostate, endometrial, and cervical cancers. Its simultaneous acquisition has been shown to outperform other imaging techniques for the detection of pelvic nodal metastases and is also a reliable modality in radiation planning. Lastly, in haematologic malignancies, PET/MR can significantly enhance lymphoma diagnosis, particularly in detecting extra-nodal involvement. It can also comprehensively assess treatment-induced changes. Furthermore, PET/MR may soon become a routine in multiple myeloma management, being a one-stop shop for evaluating bone, bone marrow, and soft tissues.

Head-to-head comparison of prostate-specific membrane antigen positron emission tomography/computed tomography and multiparametric magnetic resonance imaging in the detection of biochemical recurrence of prostate cancer: a systematic review and meta-analysis

AIM

Our main goal of this meta-analytical analysis was to evaluate the diagnostic effectiveness of prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) against multiparametric magnetic resonance imaging (mpMRI) in the context of identifying biochemical recurrence in patients with prostate cancer (PCa).

MATERIALS AND METHODS

A thorough search covering articles published until March 2023 was carried out across major databases such as PubMed, Embase, and Web of Science. Studies examining the direct comparison of PSMA PET/CT and mpMRI in patients with PCa suffering biochemical recurrence were included in the inclusion criteria. Using the renowned Quality Assessment of Diagnostic Performance Studies-2 technique, each study's methodological rigor was assessed.

RESULTS

We analyzed data from six eligible studies involving 290 patients in total. The combined data showed that for PSMA PET/CT and mpMRI, respectively, the pooled overall detection rates for recurrent PCa after definitive treatment were 0.69 (95% confidence interval [CI]: 0.45-0.89) and 0.70 (95% CI: 0.44-0.91). The detection rates for local recurrence were specifically 0.52 (95% CI: 0.39-0.65) and 0.62 (95% CI: 0.31-0.89), while they were 0.50 (95% CI: 0.26-0.74) and 0.32 (95% CI: 0.18-0.48) for lymph node metastasis. Notably, there was no discernible difference between the two imaging modalities in terms of the overall detection rate (P = 0.95). The detection rates for local recurrence and lymph node metastasis did not differ statistically significantly (P = 0.55, 0.23).

CONCLUSION

The performance of PSMA PET/CT and mpMRI in identifying biochemical recurrence in PCa appears to be comparable. However, the meta-analysis' findings came from research with modest sample sizes. In this context, more extensive research should be conducted in the future.

Deep learning-based whole-body PSMA PET/CT attenuation correction utilizing Pix-2-Pix GAN

PURPOSE

Sequential PET/CT studies oncology patients can undergo during their treatment follow-up course is limited by radiation dosage. We propose an artificial intelligence (AI) tool to produce attenuation-corrected PET (AC-PET) images from non-attenuation-corrected PET (NAC-PET) images to reduce need for low-dose CT scans.

METHODS

A deep learning algorithm based on 2D Pix-2-Pix generative adversarial network (GAN) architecture was developed from paired AC-PET and NAC-PET images. 18F-DCFPyL PSMA PET-CT studies from 302 prostate cancer patients, split into training, validation, and testing cohorts (n = 183, 60, 59, respectively). Models were trained with two normalization strategies: Standard Uptake Value (SUV)-based and SUV-Nyul-based. Scan-level performance was evaluated by normalized mean square error (NMSE), mean absolute error (MAE), structural similarity index (SSIM), and peak signal-to-noise ratio (PSNR). Lesion-level analysis was performed in regions-of-interest prospectively from nuclear medicine physicians. SUV metrics were evaluated using intraclass correlation coefficient (ICC), repeatability coefficient (RC), and linear mixed-effects modeling.

RESULTS

Median NMSE, MAE, SSIM, and PSNR were 13.26%, 3.59%, 0.891, and 26.82, respectively, in the independent test cohort. ICC for SUVmax and SUVmean were 0.88 and 0.89, which indicated a high correlation between original and AI-generated quantitative imaging markers. Lesion location, density (Hounsfield units), and lesion uptake were all shown to impact relative error in generated SUV metrics (all p < 0.05).

CONCLUSION

The Pix-2-Pix GAN model for generating AC-PET demonstrates SUV metrics that highly correlate with original images. AI-generated PET images show clinical potential for reducing the need for CT scans for attenuation correction while preserving quantitative markers and image quality.

Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography-Based Clinical Target Volume Delineation Guideline for Postprostatectomy Salvage Radiation Therapy: The PERYTON Guideline

PURPOSE

Prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) scan is the standard imaging procedure for biochemical recurrent prostate cancer postprostatectomy because of its high detection rate at low serum prostate-specific antigen levels. However, existing guidelines for clinical target volume (CTV) in prostate bed salvage external beam radiation therapy (sEBRT) are primarily based on experience-based clinical consensus and have been validated using conventional imaging modalities. Therefore, this study aimed to optimize CTV definition in sEBRT by using PSMA PET/CT-detected local recurrences (LRs).

METHODS AND MATERIALS

Patients with suspected LR on PSMA PET/CT postprostatectomy were retrospectively enrolled in 9 Dutch centers. Anonymized scans were centrally reviewed by an expert nuclear medicine physician. Each boundary of the CTV guideline from the Groupe Francophone de Radiothérapie en Urologie (GFRU) was evaluated and adapted to improve the accuracy and coverage of the area at risk of LR (CTV) on PSMA PET/CT. The proposed CTV adaptation was discussed with the radiation oncologists of the participating centers, and final consensus was reached. To assess reproducibility, the participating centers were asked to delineate 3 new cases according to the new PERYTON-CTV, and the submitted contours were evaluated using the Dice similarity coefficient (DSC).

RESULTS

After central review, 93 LRs were identified on 83 PSMA PET/CTs. The proposed CTV definition improved the coverage of PSMA PET/CT-detected LRs from 67% to 96% compared with the GFRU-CTV, while reducing the GFRU-CTV by 25%. The new CTV was highly reproducible, with a mean DSC of 0.82 (range, 0.81-0.83).

CONCLUSIONS

This study contributes to the optimization of CTV definition in postprostatectomy sEBRT by using the pattern of LR detected on PSMA PET/CT. The PERYTON-CTV is highly reproducible across the participating centers and ensures coverage of 96% LRs while reducing the GFRU-CTV by 25%.

Construction of truncated PSMA as a PET reporter gene for CAR T cell trafficking

In solid tumors, there are multiple barriers for a chimeric antigen receptor (CAR) T cell to surmount in order to reach the tumor site. For better understanding whether CAR T cells effectively infiltrate into tumor site, and simultaneously, whether there are off-target effects, real-time monitoring technologies need to be established. Cell-based positron emission tomography reporter genes have been developed to monitor engineered cells in living subjects. In this study, we reported the construction of a novel reporter gene truncated prostate-specific membrane antigen (ΔPSMA) pending for monitoring CAR T cells using 68Ga-PSMA-617 and a method for tracking the distribution of CAR T cells in vivo was developed. Data were provided to demonstrate that ΔPSMA was predominantly localized on the plasma membrane and could take up 68Ga-PSMA-617 in vitro in a time-dependent manner. And the expression of ΔPSMA did not affect CAR expression and cytolytic capacity of CAR T cells. CAR-ΔPSMA T cell xenografts in nude mice were clearly imaged by positron emission tomography 60 min after injection of 68Ga-PSMA-617. PSMA paired with 68Ga-PSMA-617 was capable of identifying approximately 1 × 104 engineered CAR T cells. The ability to image small numbers of CAR T cells in vivo would be helpful to accelerate the translation of cell-based therapies into the clinic, and it may reinforce our understanding of treatment success, failure, and toxicity.

MRI and PSMA PET/CT of Biochemical Recurrence of Prostate Cancer

Prostate cancer may recur several years after definitive treatment, such as prostatectomy or radiation therapy. A rise in serum prostate-specific antigen (PSA) level is the first sign of disease recurrence, and this is termed biochemical recurrence. Patients with biochemical recurrence have worse survival outcomes. Radiologic localization of recurrent disease helps in directing patient management, which may vary from active surveillance to salvage radiation therapy, androgen-deprivation therapy, or other forms of systemic and local therapy. The likelihood of detecting the site of recurrence increases with higher serum PSA level. MRI provides optimal diagnostic performance for evaluation of the prostatectomy bed. Prostate-specific membrane antigen (PSMA) PET radiotracers currently approved by the U.S. Food and Drug Administration demonstrate physiologic urinary excretion, which can obscure recurrence at the vesicourethral junction. However, MRI and PSMA PET/CT have comparable diagnostic performance for evaluation of local recurrence after external-beam radiation therapy or brachytherapy. PSMA PET/CT outperforms MRI in identifying recurrence involving the lymph nodes and bones. Caveats for use of both PSMA PET/CT and MRI do exist and may cause false-positive or false-negative results. Hence, these techniques have complementary roles and should be interpreted in conjunction with each other, taking the patient history and results of any additional prior imaging studies into account. Novel PSMA agents at various stages of investigation are being developed, and preliminary data show promising results; these agents may revolutionize the landscape of prostate cancer recurrence imaging in the future. ©RSNA, 2023 Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Turkbey in this issue. The slide presentation from the RSNA Annual Meeting is available for this article.

Diagnostic performance of 18F-labeled PSMA PET/CT in patients with biochemical recurrence of prostate cancer: a systematic review and meta-analysis

BACKGROUND

After initial treatment of prostate cancer, increases in prostate-specific antigen (PSA) levels commonly signify potential relapse or metastasis. 18F-labeled prostate-specific membrane antigen (PSMA) is considered a promising treatment due to its favorable physical properties.

PURPOSE

To investigate the diagnostic value of 18F-PSMA PET/CT for the recurrence and/or metastasis of biochemical recurrence of prostate cancer (BRPca).

MATERIAL AND METHODS

A comprehensive literature search was conducted in PubMed, EMBASE, Web of Science, and the Cochrane Library databases. Combined sensitivity and specificity values for the use of 18F-PSMA PET/CT in patients with BRPca were obtained. The quality of the studies was tested using the Diagnostic Accuracy Research Quality Assessment tool. Meta-analysis was performed using STATA 15 software, and heterogeneity was subsequently tested.

RESULTS

A total of 16 studies (1162 patients) were enrolled and had significant heterogeneity. The pooled sensitivity, specificity, and AUC values for 18F-PSMA PET/CT in the diagnosis of prostate recurrence and/or metastasis were 0.93 (0.89-0.95), 0.94 (0.85-0.98), and 0.96 (0,94-0.98), respectively. Meta-regression analyses showed that the sources of heterogeneity did not relate to ligands, study designs, or participants. The pooled sensitivity and specificity values of 18F-DCFPyL PET/CT were 0.90 (0.85-0.94) and 0.89 (0.85-0.93), respectively. The pooled sensitivity and specificity values of 18F-PSMA-1007 PET/CT were 0.89 (0.85-0.93) and 0.93 (0.70-0.99), respectively. The per-patient pooled sensitivity and specificity values were 0.92 (0.86-0.96) and 0.83 (0.41-0.97), respectively. The per-lesion pooled sensitivity and specificity values were 0.91 (0.86-0.94) and 0.91 (0.86-0.94), respectively.

CONCLUSION

According to our meta-analysis, 18F-PSMA PET/CT has the potential to be critical for the diagnosis of recurrence and/or metastasis in patients with BRPca.

The Role of mpMRI in the Assessment of Prostate Cancer Recurrence Using the PI-RR System: Diagnostic Accuracy and Interobserver Agreement in Readers with Different Expertise

BACKGROUND

treated prostate cancer (PCa) patients develop biochemical recurrence (BCR) in 27-53% of cases; the role of MRI in this setting is still controversial. In 2021 a panel of experts proposed a "Prostate Imaging-Recurrence Reporting" (PI-RR) score, aiming to standardize the reporting. The aim of our study is to evaluate the reproducibility of the PI-RR scoring system among readers with different expertise.

METHODS

in this monocentric, retrospective observational study, the images of patients who underwent MRI with BCR from January 2017 to January 2022 were analyzed by two radiologists and a radiology resident. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were obtained. Interobserver agreement was calculated. The percentage of the PI-RR score of 3 was estimated to find out the proportion of uncertain exams reported among the readers.

RESULTS

a total of seventy-six patients were included in our study: eight previously treated with RT and sixty-eight who underwent surgery. The accuracy range was 75-80%, the sensitivity 68.4-71.1%, the specificity 81.6-89.5%, PPV 78.8-87.1%, and NPV 72.1-75.6%. The inter-reader agreement using a binary evaluation (PI-RR ≥ 3 as positive mpMRI) demonstrated a correlation coefficient (k) of 0.74 (95% CI: 0.62-0.87). The percentage for the PI-RR score of 3 was 6.6% for reader one, 14.5% for reader two, and 2.6% for reader three.

CONCLUSION

this study confirmed the good accuracy of mpMRI in the detection of local recurrence of PCa and the good reproducibility of PI-RR score among all readers, confirming it to be a promising tool for the standardization of the assessment of patients with BCR.

Mapping of Local Recurrences After Radical Prostatectomy Using 68-Gallium-Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography: Implications for Postprostatectomy Radiation Therapy Clinical Target Volumes

PURPOSE

Our objective is to describe the distribution of local recurrences after radical prostatectomy (RP) as delineated using 68-Gallium-prostate-specific membrane antigen positron emission tomography/computed tomography (⁶⁸Ga-PSMA PET/CT) to identify areas where current consensus guideline clinical target volumes (CTVs) are insufficient or excessive and to identify predictors of recurrence location within the fossa.

METHODS AND MATERIALS

Retrospective review of databases from 2 tertiary referral centers was performed to identify patients who underwent ⁶⁸Ga-PSMA PET/CT for biochemical recurrence after RP. Those with a component of local recurrence were included for further analysis. The epicenter of each recurrence was defined relative to reference points in 3 axes, categorized into 1 of 7 levels in the superior/inferior axis relative to the vesicourethral anastomosis, and recorded as within or outside the Faculty of Radiation Oncology Genito-urinary Group (FROGG) and Radiation Therapy Oncology Group consensus CTVs. Univariate and multivariate analysis was performed to identify predictors of recurrence location based on clinical and histopathologic variables.

RESULTS

One thousand forty-nine ⁶⁸Ga-PSMA PET/CT scans were reviewed. One hundred forty sites of local recurrence were identified on 132 scans. Relative to the vesicourethral anastomosis, 13 (9%), 31 (22%), 17 (12%), 24 (17%), 27 (19%), 20 (14%), and 8 (6%) recurrences occurred >5 mm inferior; within 5 mm above or below; and 6 to 15 mm, 16 to 25 mm, 26 to 35 mm, 36 to 45 mm, and >45 mm superiorly, respectively. Thirteen (9%) and 2 (1.4%) recurrences occurred beyond the FROGG and Radiation Therapy Oncology Group consensus CTVs, respectively, with all below the inferior CTV margin.

CONCLUSIONS

In the largest study to date mapping local recurrences after RP in 3-dimensions, we provide several insights to inform future contouring guidelines; in particular, 9% of recurrences occurred inferior to the FROGG CTV.

PSMA-based 18F-DCFPyL PET: a better choice than multiparametric MRI for prostate cancer diagnosis?

Owing to the high tissue contrast, multiparametric MRI (mpMRI) has already been the most widely applied imaging method for prostate cancer. Recently, prostate-specific membrane antigen (PSMA) ligands for nuclear imaging are emerging as a promising modality in prostate cancer, especially since the 2 PET/CT agents (⁶⁸Ga-PSMA-11 and ¹⁸F-DCFPy) approved by U.S. Food and Drug Administration (FDA). However, limited studies have performed the comparison of mpMRI versus recently approved ¹⁸F-DCFPyL PET/CT. In this issue of AJNMMI, Lu et al. compared the performance of ¹⁸F-DCFPyL PET/CT and pelvic mpMRI in intermediate-high risk and biochemical recurrent prostate cancer patients. The results demonstrated the two modalities have a good concordance rate for patient-based analysis, and ¹⁸F-DCFPyL PET/CT has a better diagnostic performance in detecting lymph node metastases and bone metastases for lesion-based analysis. The use of ¹⁸F-DCFPyL PET/CT provides more diagnostic confidence to better assess prostate cancer lesions.

Changes in Management After 18F-DCFPyL PSMA PET in Patients Undergoing Postprostatectomy Radiotherapy, with Early Biochemical Response Outcomes

Prostate-specific membrane antigen (PSMA) tracers have increased sensitivity in the detection of prostate cancer, compared with conventional imaging. We assessed the management impact of ¹⁸F-DCFPyL PSMA PET/CT in patients with prostate-specific antigen (PSA) recurrence after radical prostatectomy (RP) and report early biochemical response in patients who underwent radiation treatment. Methods: One hundred patients were enrolled into a prospective study, with a prior RP for prostate cancer, a PSA of 0.2-2.0 ng/mL, and no prior treatment. All patients underwent diagnostic CT and PSMA PET/CT, and management intent was completed at 3 time points (original, post-CT, and post-PSMA) and compared. Patients who underwent radiotherapy with 6-mo PSA response data are presented. Results: Ninety-eight patients are reported, with a median PSA of 0.32 ng/mL (95% CI, 0.28-0.36), pT3a/b disease in 71.4%, and an International Society of Urological Pathology grade group of at least 3 in 59.2%. PSMA PET/CT detected disease in 46.9% of patients, compared with 15.5% using diagnostic CT (PSMA PET, 29.2% local recurrence and 29.6% pelvic nodal disease). A major change in management intent was higher after PSMA than after CT (12.5% vs. 3.2%, P = 0.010), as was a moderate change in intent (31.3% vs. 13.7%, P = 0.001). The most common change was an increase in the recommendation for elective pelvic radiation (from 15.6% to 33.3%), nodal boost (from 0% to 22.9%), and use of concurrent androgen deprivation therapy (ADT) (from 22.9% to 41.7%) from original to post-PSMA intent because of detection of nodal disease. Eighty-six patients underwent ¹⁸F-DCFPyL-guided radiotherapy. Fifty-five of 86 patients either did not receive ADT or recovered after ADT, with an 18-mo PSA response from 0.32 to 0.02 ng/mL; 94.5% of patients had a PSA of no more than 0.20 ng/mL, and 74.5% had a PSA of no more than 0.03 ng/mL. Conclusion: ¹⁸F-DCFPyL PET/CT has a significant impact on management intent in patients being considered for salvage radiotherapy after RP with PSA recurrence. Increased detection of disease, particularly in the pelvic lymph nodes, resulted in increased pelvic irradiation and concurrent ADT use. Early results in patients who are staged with ¹⁸F-DCFPyL PET/CT show a favorable PSA response.

[18F]DCFPyL PET/CT for Imaging of Prostate Cancer

Prostate-specific membrane antigen (PSMA)-directed positron emission tomography (PET) has gained increasing interest for imaging of men affected by prostate cancer (PC). In recent years, ⁶⁸Ga-labeled PSMA compounds have been widely utilized, although there is a trend towards increased utilization of ¹⁸F-labeled agents. Among others, [¹⁸F]DCFPyL (piflufolastat F 18, PYLARIFY) has been tested in multiple major trials, such as OSPREY and CONDOR, which provided robust evidence on the clinical utility of this compound for staging, restaging, and change in management. Recent explorative prospective trials have also utilized [¹⁸F]DCFPyL PET/CT for response assessment, e.g., in patients under abiraterone or enzalutamide, rendering this ¹⁸F-labeled PSMA radiotracer as an attractive biomarker for image-guided strategies in men with PC. After recent approval by the U.S. Food and Drug Administration, one may expect more widespread use, not only in the U.S., but also in Europe in the long term. In the present review, we will provide an overview of the current clinical utility of [¹⁸F]DCFPyL in various clinical settings for men with PC.

Radiating the prostate bed in relapsed oligometastatic prostate cancer: How comprehensive should we be?

PURPOSE

A subset of patients with high-risk pathological features at radical prostatectomy recur with oligometastatic disease. The aim of this study is to investigate the rate of prostate bed recurrence, with or without history of prostate bed irradiation (PBRT), in oligometastatic prostate cancer (OMPC) patients after metastasis-directed therapy (MDT).

METHODS

We performed a retrospective analysis of hormone-sensitive OMPC patients treated initially with curative-intent radical prostatectomy followed by disease recurrence and metastasis-directed stereotactic ablative radiotherapy (SABR) at our institution. Prostate bed recurrence rates were compared between patients who had PBRT at any point (i.e., before oligometastatic diagnosis or concurrently with MDT) versus those with no history of PBRT.

RESULTS

Seventy-seven patients were included, and 68.8% had received PBRT. There were no significant differences in baseline characteristics between those who had received and had not received PBRT. There were five prostate bed recurrences following MDT, specifically with a 24-month cumulative incidence of 30.4% in patients who did not have PBRT and 2.4% in those who did (p = 0.03). Three of the five recurrences were isolated to the prostate bed at time of recurrence.

CONCLUSIONS

Relapsed oligometastatic prostate cancer patients who have not received maximal local consolidative therapy to the prostate bed may have higher rates of local failure. Prospective studies are warranted investigating when prostate bed irradiation should be considered for patients after radical prostatectomy who ultimately have oligometastatic prostate cancer.

Piflufolastat F 18: Diagnostic First Approval

Piflufolastat F 18 (PYLARIFY^®) is an ¹⁸F-labelled diagnostic imaging agent that has been developed by Progenics Pharmaceuticals Inc., a Lantheus company, for positron emission tomography (PET) that targets prostate-specific membrane antigen (PSMA). Piflufolastat F 18 was approved in the USA on 27 May 2021 for PET of PSMA positive lesions in men with prostate cancer with suspected metastasis who are candidates for initial definitive therapy or with suspected recurrence based on elevated serum prostate specific antigen (PSA) level. This article summarizes the milestones in the development of piflufolastat F 18 leading to this approval as a radioactive diagnostic agent in prostate cancer.

Synthesis and preclinical evaluation of an Al18F radiofluorinated bivalent PSMA ligand

Prostate-specific membrane antigen (PSMA) has become as an outstanding prostate cancer-related target for diagnostic imaging and targeted radiotherapy. Clinical studies on a few PSMA radiotracers are currently underway to determine their efficacy as imaging agents to detect prostate cancer. To improve tumor retention and tumor-to-normal tissue contrast, we herein report the synthesis and preclinical evaluation of an Al¹⁸F-labeled bivalent PSMA ligand (¹⁸F-Bi-PSMA). ¹⁸F-Bi-PSMA was successful automated preparation and in vitro evaluation showed that ¹⁸F-Bi-PSMA was potent binding affinity, high specificity, and rapid internalization in PSMA-expressing cells. Biodistribution studies revealed a high and specific tumor uptake of 20.5 ± 3.5 %ID/g in 22Rv1 tumor-bearing mice. Furthermore, compared to the clinically used monomeric PSMA-targeting tracers, ⁶⁸Ga-PSMA-11 and ¹⁸F-PSMA-1007, ¹⁸F-Bi-PSMA exhibited improved pharmacokinetics and higher tumor uptake, as well as better tumor-to-normal tissue contrast, resulting in considerably high imaging quality. Our findings indicated that the bivalent PSMA radioligand, ¹⁸F-Bi-PSMA, was successfully synthesized and ideal imaging properties.

Mars Shot for Nuclear Medicine, Molecular Imaging, and Molecularly Targeted Radiopharmaceutical Therapy

The Society of Nuclear Medicine and Molecular Imaging created the Value Initiative in 2017 as a major component of its strategic plan to further demonstrate the value of molecular imaging and molecularly targeted radiopharmaceutical therapy to patients, physicians, payers, and funding agencies. The research and discovery domain, 1 of 5 under the Value Initiative, has a goal of advancing the research and development of diagnostic and therapeutic nuclear medicine. Research and discovery efforts and achievements are essential to ensure a bright future for NM and to translate science to practice. Given the remarkable progress in the field, leaders from the research and discovery domain and society councils identified 5 broad areas of opportunity with potential for substantive growth and clinical impact. This article discusses these 5 growth areas, identifying specific areas of particularly high importance for future study and development. As there was an understanding that goals should be both visionary yet achievable, this effort was called the Mars shot for nuclear medicine.

Patterns of disease detection using [18F]DCFPyL PET/CT imaging in patients with detectable PSA post prostatectomy being considered for salvage radiotherapy: a prospective trial

PURPOSE

Prostate-specific membrane antigen (PSMA) PET/CT is increasingly used in patients with biochemical recurrence post prostatectomy to detect local recurrence and metastatic disease at low PSA levels. The aim of this study was to assess patterns of disease detection, predictive factors and safety using [¹⁸F]DCFPyL PET/CT versus diagnostic CT in patients being considered for salvage radiotherapy with biochemical recurrence post prostatectomy.

METHODS

We conducted a prospective trial recruiting 100 patients with detectable PSA post prostatectomy (PSA 0.2-2.0 ng/mL) and referred for salvage radiotherapy from August 2018 to July 2020. All patients underwent a PSMA PET/CT using the [¹⁸F]DCFPyL tracer and a diagnostic CT. The detection rates of [¹⁸F]DCFPyL PET/CT vs diagnostic CT were compared and patterns of disease are reported. Clinical patient and tumour characteristics were analysed for predictive utility. Thirty-day post-scan safety is reported.

RESULTS

Of 100 patients recruited, 98 were suitable for analysis with a median PSA of 0.32 ng/mL. [¹⁸F]DCFPyL PET/CT was positive 46.4% and equivocal 5.2%, compared to 15.5% positivity for diagnostic CT. Local recurrence was detected on [¹⁸F]DCFPyL PET/CT in 28.5%, nodal disease in 27.5% and bony metastases in 6.1% of patients. Both ISUP grade group (p < 0.001) and pre-scan PSA (p = 0.029) were significant predictors of [¹⁸F]DCFPyL PET/CT positivity, and logistic regression generated probabilities combining the two showed improved prediction rates. No significant safety events were reported post [¹⁸F]DCFPyL administration.

CONCLUSIONS

[¹⁸F]DCFPyL PET/CT increases detection of disease in patients with biochemical recurrence post prostatectomy compared to diagnostic CT. Patients being considered for salvage radiotherapy with a PSA >0.2 ng/mL should be considered for [¹⁸F]DCFPyL PET/CT scan.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry Number: ACTRN12618001530213 ( http://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=375932&isReview=true ).

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.

Prostate Magnetic Resonance Imaging for Local Recurrence Reporting (PI-RR): International Consensus -based Guidelines on Multiparametric Magnetic Resonance Imaging for Prostate Cancer Recurrence after Radiation Therapy and Radical Prostatectomy

BACKGROUND

Imaging techniques are used to identify local recurrence of prostate cancer (PCa) for salvage therapy and to exclude metastases that should be addressed with systemic therapy. For magnetic resonance imaging (MRI), a reduction in the variability of acquisition, interpretation, and reporting is required to detect local PCa recurrence in men with biochemical relapse after local treatment with curative intent.

OBJECTIVE

To propose a standardised method for image acquisition and assessment of PCa local recurrence using MRI after radiation therapy (RP) and radical prostatectomy (RT).

EVIDENCE ACQUISITION

Prostate Imaging for Recurrence Reporting (PI-RR) was formulated using the existing literature. An international panel of experts conducted a nonsystematic review of the literature. The PI-RR system was created via consensus through a combination of face-to-face and online discussions.

EVIDENCE SYNTHESIS

Similar to with PI-RADS, based on the best available evidence and expert opinion, the minimum acceptable MRI parameters for detection of recurrence after radiation therapy and radical prostatectomy are set. Also, a simplified and standardised terminology and content of the reports that use five assessment categories to summarise the suspicion of local recurrence (PI-RR) are designed. PI-RR scores of 1 and 2 are assigned to lesions with a very low and low likelihood of recurrence, respectively. PI-RR 3 is assigned if the presence of recurrence is uncertain. PI-RR 4 and 5 are assigned for a high and very high likelihood of recurrence, respectively. PI-RR is intended to be used in routine clinical practice and to facilitate data collection and outcome monitoring for research.

CONCLUSIONS

This paper provides a structured reporting system (PI-RR) for MRI evaluation of local recurrence of PCa after RT and RP.

PATIENT SUMMARY

A new method called PI-RR was developed to promote standardisation and reduce variations in the acquisition, interpretation, and reporting of magnetic resonance imaging for evaluating local recurrence of prostate cancer and guiding therapy.

[18F]DCFPyL PET/CT in detection and localization of recurrent prostate cancer following prostatectomy including low PSA < 0.5 ng/mL

PURPOSE

The primary aim of this retrospective multicenter analysis was to assess the performance of PSMA PET/CT using [¹⁸F]DCFPyL in the detection and localization of recurrent prostate cancer post radical prostatectomy (RP). Particular reference is given to low PSA groups < 0.5 ng/mL to aid discussion around the inclusion of this group in PSMA guidelines and funding pathways.

METHODS

Retrospective analysis of combined PSMA database patients from centers in Australia and New Zealand. Two hundred twenty-two patients presenting with recurrence post RP were stratified into five PSA groups (ng/mL): 0-0.19, 0.2-0.49, 0.5-0.99, 1-1.99, and ≥ 2. Lesions detected by [¹⁸F]DCFPyL PET/CT were recorded as local recurrence, locoregional nodes, and metastases.

RESULTS

Of 222 patients, 155 (69.8%) had evidence of abnormal uptake suggestive of recurrent prostate cancer. The detection efficacies for [¹⁸F]DCFPyL PET/CT were 91.7% (44/48) for PSA levels ≥ 2 ng/mL, 82.1% (23/28) for PSA levels 1-1.99 ng/mL, 62.8% (27/43) for PSA levels 0.5-0.99 ng/mL, 58.7% (54/92) for PSA levels 0.2-0.49 ng/mL, and 63.6% (7/11) for PSA levels ≤ 0.2 ng/mL. In those with PSA < 0.5 ng/mL, 47.6% (49/103) had detectable lesions, 71.4% (35/49) had disease confined to the pelvis, 22.4% (11/49) had prostate bed recurrence, 49.0% (24/49) had pelvic lymph nodes, and 28.6% (14/49) had extra pelvic disease.

CONCLUSION

[¹⁸F]DCFPyL PET/CT has a high detection rate in recurrence following RP even at low PSA levels with similar detection levels in the PSA subgroups < 0.5 ng/mL. Employing rigid PSA thresholds when constructing guidelines for PSMA PET/CT funding eligibility may result in a significant number of patients below such thresholds having delayed or inappropriate treatment.