Response Evaluation Criteria in PSMA PET/CT (RECIP 1.0) in Metastatic Castration-resistant Prostate Cancer

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

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

Prostate Cancer Radioligand Therapy: Beta-labeled Radiopharmaceuticals

Prostate cancer is the most common malignancy in men worldwide, with an estimated 174,650 new cases per year in the United States, and the second cancer-related cause of death, after lung cancer, with 31,620 deaths per year. While the 5 year survival rate for prostate cancer in patients without metastatic spread is nearly 100%, those with distant metastases have 5 year survival rates of approximately 30%. Initial diagnosis and assessment are based on PSA levels, Gleason score (derived from prostate biopsy), and advanced imaging modalities, including prostate MR imaging and PSMA-PET/computed tomography in patients with high-risk features.

Treatment Response Imaging in Prostate Cancer

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

Prostate-Specific Membrane Antigen Positron Emission Tomography Oncological Applications beyond Prostate Cancer in Comparison to Other Radiopharmaceuticals

BACKGROUND

Prostate-specific membrane antigen (PSMA) is a type II transmembrane glycoprotein overexpressed on the surface of tumor cells in most of the patients affected by prostate adenocarcinoma (PCa). However, PSMA expression has also been demonstrated in the endothelial cells of newly formed vessels of various solid tumors, suggesting a role for PSMA in neoangiogenesis. In this scenario, gallium-68 (68Ga) or fluoro-18 (18F)-labeled PSMA positron emission tomography (PET) may play a role in tumors other than PCa, generally evaluated employing other radiopharmaceuticals targeting different pathways. This review aims to investigate the detection rate of PSMA-PET compared to other radiopharmaceuticals (especially [18F]FDG) in non-prostate tumors to identify patients who may benefit from the use of such a theragnostic agent.

METHODS

We performed a bibliographic search on three different databases until February 2024 using the following terms: "positron emission tomography", "PET", "PET/CT", "Prostate-specific membrane antigen", "PSMA", "non-prostate", "not prostate cancer", "solid tumor", "FDG", "Fluorodeoxyglucose", "FAPi", "FET", "MET", "DOPA", "choline", "FCH", "FES", "DOTATOC", "DOTANOC", and "DOTATATE". Only original articles edited in English with at least 10 patients were included.

RESULTS

Out of a total of 120 articles, only 25 original articles comparing PSMA with other radiotracers were included in this study. The main evidence was demonstrated in renal cell carcinoma, where PSMA showed a higher detection rate compared to [18F]FDG PET/CT, with implications for patient management. PSMA PET may also improve the assessment of other entities, such as gliomas, in defining regions of early neoangiogenesis. Further data are needed to evaluate the potential role of PSMA-PET in triple-negative breast cancer as a novel therapeutic vascular target. Finally, unclear applications of PSMA-PET include thyroid and gastrointestinal tumors.

CONCLUSIONS

The present review shows the potential use of PSMA-labeled PET/CT in solid tumors beyond PCa, underlining its value over other radiopharmaceuticals (mainly [18F]FDG). Prospective clinical trials with larger sample sizes are crucial to further investigate these possible clinical applications.

Safety and Efficacy of Extended Therapy with [177Lu]Lu-PSMA: A German Multicenter Study

Prospective results have demonstrated favorable safety and efficacy of [177Lu]Lu-PSMA radiopharmaceutical therapy for up to 6 cycles in men with metastatic castration-resistant prostate cancer. However, no systematic data are available outlining the feasibility of extended therapy beyond 6 cycles. We aim to evaluate the safety and efficacy of extended [177Lu]Lu-PSMA radiopharmaceutical therapy in patients who have received more than 6 cycles. Methods: In total, 111 patients were included in this multicenter retrospective analysis. Based on individual decisions, patients underwent uninterrupted continuation of therapy (continuous treatment) or reexposure after a therapy break (rechallenge treatment) between 2014 and 2023. Overall survival, 50% prostate-specific antigen (PSA) decline (measured 8-12 wk after treatment initiation or rechallenge), PSMA PET response, and grades per Common Terminology Criteria for Adverse Events were assessed. χ2 tests, multivariable Cox regression analysis, and log-rank tests were applied for statistical analyses. Results: Patients received extended treatment with [177Lu]Lu-PSMA, either as a continuous treatment (43/111, 38.7%) or as a rechallenge (68/111, 61.3%) treatment, with median cumulative doses of 57.4 or 60.8 GBq, respectively. Overall survival from the initiation of [177Lu]Lu-PSMA was 31.3, 23.2, and 40.2 mo for the entire cohort, the continuous treatment group, and the rechallenge treatment group, respectively. The initial 50% PSA decline was significantly higher in the retreated group than in the continuous group (57/63 [90.4%] vs. 26/42 [61.9%]; P = 0.006). A 50% PSA decline was observed in 23 of 62 patients (37.1%) after the first rechallenge. The rate of grades 3-4 toxicity was comparable between continuous and rechallenge treatments (anemia, 7/43 [16.3%] vs. 13/68 [19.1%)], P = 0.6; leukocytopenia, 1/43 [2.3%] vs. 2/67 [3.0%], P = 0.3; thrombocytopenia, 3/43 [7.0%] vs. 3/68 [4.4%], P = 0.3; renal, 2/43 [4.7%] vs. 5/68 [7.4%], P = 0.2). Conclusion: Extended therapy with [177Lu]Lu-PSMA is safe and has not been associated with increased grades 3-4 toxicity. Patient candidates for extended treatment experienced a favorable median survival of 31.3 mo from the first administration. Response under [177Lu]Lu-PSMA rechallenge demonstrated preserved efficacy of [177Lu]Lu-PSMA after a treatment break.

RECIP 1.0 Predicts Progression-Free Survival After [177Lu]Lu-PSMA Radiopharmaceutical Therapy in Patients with Metastatic Castration-Resistant Prostate Cancer

Response Evaluation Criteria in Prostate-Specific Membrane Antigen Imaging (RECIP) 1.0 is an evidence-based framework to evaluate therapeutic efficacy in metastatic prostate cancer using prostate-specific membrane antigen (PSMA) PET/CT. This study aimed to evaluate the associations of interim PSMA PET/CT by RECIP 1.0 with short-term outcome after radiopharmaceutical treatment. Methods: This multicenter retrospective study included patients with metastatic castration-resistant prostate cancer who underwent [177Lu]Lu-PSMA radiopharmaceutical therapy at 3 academic centers and received PSMA PET/CT at baseline and at 12 wk. Pairs of PSMA PET/CT images were assessed by 5 readers for visual RECIP 1.0. The primary outcome was the association of RECIP with prostate-specific antigen progression-free survival (PSA-PFS) by Kaplan-Meier analysis. Results: In total, 124 of 287 screened patients met the inclusion criteria, with 0 (0%), 29 (23%), 54 (44%), and 41 (33%) of those 124 patients having complete response, partial response, stable disease, or progressive disease (PD) by visual RECIP 1.0, respectively. Patients with visual RECIP PD had a significantly shorter PSA-PFS than those with RECIP stable disease or with RECIP partial response (2.6 vs. 6.4 vs. 8.4 mo; P < 0.001). The median PSA-PFS among patients with RECIP PD versus those with non-RECIP PD was 2.6 versus 7.2 mo (hazard ratio, 13.0; 95% CI, 7.0-24.1; P < 0.001). Conclusion: PSMA PET/CT by RECIP 1.0 after 2 cycles of [177Lu]Lu-PSMA is prognostic for PSA-PFS. PSMA PET/CT by RECIP 1.0 may be used in earlier stages of prostate cancer to evaluate drug efficacy and to predict progression-free survival.

Prostate Cancer Theranostics With 177Lu-PSMA

This review paper highlights the transformative role of PSMA-targeted diagnostics and therapy in prostate cancer management, particularly focusing on 177Lu-PSMA-617, approved by the FDA and EMA for metastatic castration-resistant prostate cancer (mCRPC) patients post-chemotherapy and ARPI treatment. Originating from the VISION trial's success, this paper navigates the current radioligand therapy (RLT) indications, emphasizing practical patient selection, planning, and treatment execution. It critically examines Lu-PSMA's comparative effectiveness against cabazitaxel and Ra-223, addressing decision-making dilemmas for mCRPC treatments. Furthermore, the paper discusses Lu-PSMA in chemotherapy-naïve patients and its application in hormone-sensitive prostate cancer, underlined by ongoing global studies. A significant concern is Lu-PSMA's long-term safety profile, particularly nephrotoxicity risks, necessitating further investigation. The possibility of Lu-PSMA rechallenge in responsive patients is explored, stressing the need for comprehensive analyses and real-world data to refine treatment protocols. Conclusively, PSMA-targeted therapy marks a significant advance in prostate cancer therapy, advocating for its integration into a multimodal, patient-centric treatment approach. The review underscores the imperative for additional comparative studies to optimize treatment sequences and outcomes, ultimately enhancing long-term prognosis and disease control in prostate cancer management.

Clinical Positron Emission Tomography/Computed Tomography: Quarter-Century Transformation of Prostate Cancer Molecular Imaging

Although positron emission tomography/computed tomography (PET/CT) underwent rapid growth during the last quarter-century, becoming a new standard-of-care for imaging most cancer types, CT and bone scan remained the gold standard for patients with prostate cancer. This occurred as 2-fluorine-18-fluoro-2-deoxy-d-glucose was perceived to have a limited role owing to low sensitivity in many patients. A resurgence of interest occurred with the use of fluorine-18-sodium-fluoride PET/CT as a replacement for bone scintigraphy, and then choline, fluciclovine, and dihydrotestosterone (DHT) PET/CT as prostate "specific" radiotracers. The last decade, however, has seen a true revolution with the meteoric rise of prostate-specific membrane antigen PET/CT.

Prognostic Performance of RECIP 1.0 Based on [18F]PSMA-1007 PET in Prostate Cancer Patients Treated with [177Lu]Lu-PSMA I&T

In metastatic castration-resistant prostate cancer (mCRPC) patients treated with prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT), the recently proposed criteria for evaluating response to PSMA PET (RECIP 1.0) based on 68Ga- and 18F-labeled PET agents provided prognostic information in addition to changes in prostate-specific antigen (PSA) levels. Our aim was to evaluate the prognostic performance of this framework for overall survival (OS) in patients undergoing RLT and imaged with [18F]PSMA-1007 PET/CT and compare the prognostic performance with the PSA-based response assessment. Methods: In total, 73 patients with mCRPC who were scanned with [18F]PSMA-1007 PET/CT before and after 2 cycles of RLT were retrospectively analyzed. We calculated the changes in serum PSA levels (ΔPSA) and quantitative PET parameters for the whole-body tumor burden (SUVmean, SUVmax, PSMA tumor volume, and total lesion PSMA). Men were also classified following the Prostate Cancer Working Group 3 (PCWG3) criteria for ΔPSA and RECIP 1.0 for PET imaging response. We performed univariable Cox regression analysis, followed by multivariable and Kaplan-Meier analyses. Results: Median OS was 15 mo with a median follow-up time of 14 mo. Univariable Cox regression analysis provided significant associations with OS for ΔPSA (per percentage, hazard ratio [HR], 1.004; 95% CI, 1.002-1.007; P < 0.001) and PSMA tumor volume (per unit, HR, 1.003; 95% CI, 1.000-1.005; P = 0.03). Multivariable Cox regression analysis confirmed ΔPSA (per percentage, HR, 1.004; 95% CI, 1.001-1.006; P = 0.006) as an independent prognosticator for OS. Kaplan-Meier analyses provided significant segregation between individuals with versus those without any PSA response (19 mo vs. 14 mo; HR, 2.00; 95% CI, 0.95-4.18; P = 0.04). Differentiation between patients with or without progressive disease (PD) was also feasible when applying PSA-based PCWG3 (19 mo vs. 9 mo for non-PD and PD, respectively; HR, 2.29; 95% CI, 1.03-5.09; P = 0.01) but slightly failed when applying RECIP 1.0 (P = 0.08). A combination of both response systems (PCWG3 and RECIP 1.0), however, yielded the best discrimination between individuals without versus those with PD (19 mo vs. 8 mo; HR, 2.78; 95% CI, 1.32-5.86; P = 0.002). Conclusion: In patients with mCRPC treated with RLT and imaged with [18F]PSMA-1007, frameworks integrating both the biochemical (PCWG3) and PET-based response (RECIP 1.0) may best assist in identifying subjects prone to disease progression.

Pre-treatment 68 Ga-PSMA-11 PET/CT Prognostic Value in Predicting Response to 177Lu-PSMA-I&T Therapy and Patient Survival

PURPOSE

To assess the prognostic value of pre-treatment [68Ga]Ga-PSMA-11 PET/CT and other baseline clinical characteristics in predicting prostate cancer (PCa) patients response to [177Lu]Lu-PSMA (PSMA-I&T), as well as patient survival.

PROCEDURES

In this retrospective study, 81 patients who received [177Lu]Lu-PSMA-I&T between October 2018 and January 2023 were reviewed. Eligible patients had metastatic castration-resistant PCa, underwent pre-treatment [68Ga]Ga-PSMA-11 PET/CT, and had serum prostate-specific antigen (PSA) levels available. On PET/CT images, SUVmax, SULmax, SUVpeak, and SULpeak of the most-avid tumoral lesion, as well as SUVmean of the parotid gland (P-SUVmean) and liver (L-SUVmean), were measured. Also, whole-body PSMA tumour volume (PSMA-TV) and total lesion PSMA (TL-PSMA) were calculated. To interpret treatment response after [177Lu]Lu-PSMA-I&T, a composite of PSA values and [68Ga]Ga-PSMA-11 PET/CT findings were considered. The outcomes were dichotomised into progressive versus controlled (stable disease or partial response) disease. Then, the association of baseline parameters with patient response was evaluated. Also, survival analyses were performed to assess baseline parameters in predicting overall survival.

RESULTS

Sixty patients (age:73 ± 8, PSA:185 ± 371) were included. Patients received at least one cycle of [177Lu]Lu-PSMA therapy (median = 4). Overall, half of the patients showed disease progression. In the progressive versus controlled disease evaluation, the highest SULmax, as well as SUVmax and SULmax to both backgrounds (L-SUVmean and P-SUVmean), were significantly correlated with the outcome (p-values < 0.05). In the multivariate analysis, only SULmax to the L-SUVmean remained significant (p-value = 0.038). The best cut-off was 8 (AUC = 0.71). With a median follow-up of 360 days, 11 mortal events were documented. In the multivariate survival analysis, only SULmax to P-SUVmean (cut-off = 2.4; p-value = 0.043) retained significance (hazard ratio = 4.0).

CONCLUSIONS

A greater level of PSMA uptake, specifically higher tumour-to-background uptake in the hottest lesion, may hold substantial prognostic significance, considering both [177Lu]Lu-PSMA-I&T response and patient survival. These ratios may have the potential to be used for PCa patient selection for radioligand therapy.

Restaging With Prostate-Specific Membrane Antigen Imaging in Metastatic Castration-Resistant Prostate Cancer: When Seeing More Is Detrimental to Care

#PSMA is amazing new tech but is using it to expedite the call of disease progression helping #ProstateCancer patients?

Differences and Common Ground in 177Lu-PSMA Radioligand Therapy Practice Patterns: International Survey of 95 Theranostic Centers

177Lu-labeled prostate-specific membrane antigen (PSMA) radioligand therapy effectively treats metastatic castration-resistant prostate cancer. Patients requiring treatment, and consequently the number of theranostic centers, are expected to increase significantly after Food and Drug Administration and European Medicines Agency approval. This requires standardization or harmonization among theranostic centers. The aim of this study was to assess operational differences and similarities among 177Lu-PSMA treatment centers. Methods: A questionnaire comprising 62 items, designed by a core team of 5 physicians and externally reviewed by international experts, was developed. Study participants were asked to provide answers about their center, patient selection, radiopharmaceuticals, clinical assessment before and after 177Lu-PSMA treatments, laboratory values, treatment discontinuation, posttreatment imaging, and general information. An invitation e-mail to participate in the study was sent in June 2022. Duplicates were removed to allow for only one valid response per center. Results: Ninety-five of 211 (45%) contacted centers completed the questionnaire. Most participating centers were in Europe (51%), followed by America (22%) and Asia (22%). During the 12 mo before this study, a total of 5,906 patients received 177Lu-PSMA therapy at the 95 participating centers. Most of these patients were treated in Europe (2,840/5,906; 48%), followed by Asia (1,313/5,906; 22%) and Oceania (1,225/5,906; 21%). PSMA PET eligibility for 177Lu-PSMA was determined most frequently using 68Ga-PSMA-11 (77%). Additional pretherapy imaging included 18F-FDG PET/CT, CT, renal scintigraphy, and bone scintigraphy at 41 (49%), 27 (32%), 25 (30%), and 13 (15%), respectively, of the 84 centers for clinical standard of care, compassionate care, or local research protocols and 11 (26%), 25 (60%), 9 (21%), and 28 (67%), respectively, of the 42 centers for industry-sponsored trials. PSMA PET eligibility criteria included subjective qualitative assessment of PSMA positivity at 33% of centers, VISION criteria at 23%, and TheraP criteria at 13%. The mean standard injected activity per cycle was 7.3 GBq (range, 5.5-11.1 GBq). Sixty-two (65%) centers applied standardized response assessment criteria, and PSMA PET Progression Criteria were the most applied (37%). Conclusion: Results from this international survey revealed interinstitutional differences in several aspects of 177Lu-PSMA radionuclide therapy, including patient selection, administered activity, and the response assessment strategy. Standardization or harmonization of protocols and dedicated training are desirable in anticipation of increasing numbers of patients and theranostic centers.

Impact of PSMA PET on Prostate Cancer Management

OPINION STATEMENT

PSMA-PET has been a practice-changing imaging biomarker for the management of men with PCa. Research suggests improved accuracy over conventional imaging and other PET radiotracers in many contexts. With multiple approved PSMA-targeting radiotracers, PSMA PET will become even more available in clinical practice. Its increased use requires an understanding of the prospective data available and caution when extrapolating from prior trial data that utilized other imaging modalities. Future trials leveraging PSMA PET for treatment optimization and management decision-making will ultimately drive its clinical utility.

Prostate-Specific Membrane Antigen: Gateway to Management of Advanced Prostate Cancer

Prostate-specific membrane antigen (PSMA) as a transmembrane protein is overexpressed by prostate cancer (PC) cells and is accessible for binding antibodies or low-molecular-weight radioligands due to its extracellular portion. Successful targeting of PSMA began with the development of humanized J591 antibody. Due to their faster clearance compared to antibodies, small-molecule radioligands for targeted imaging and therapy of PC have been favored in recent development efforts. PSMA positron emission tomography (PET) imaging has higher diagnostic performance than conventional imaging for initial staging of high-risk PC and biochemical recurrence detection/localization. However, it remains to be demonstrated how to integrate PSMA PET imaging for therapy response assessment and as an outcome endpoint measure in clinical trials. With the recent approval of 177Lu-PSMA-617 by the US Food and Drug Administration for metastatic castration-resistant PC progressing after chemotherapy, the high value of PSMA-targeted therapy was confirmed. Compared to standard of care, PSMA-based radioligand therapy led to a better outcome and a higher quality of life. This review, focusing on the advanced PC setting, provides an overview of different approved and nonapproved PSMA-targeted imaging and therapeutic modalities and discusses the future of PSMA-targeted theranostics, also with an outlook on non-radiopharmaceutical-based PSMA-targeted therapies.

Standardized PSMA-PET Imaging of Advanced Prostate Cancer

Imaging of advanced prostate cancer is a challenging task, as it requires longitudinal characterization of disease extent in a standardized way to enable appropriate treatment selection and evaluation of treatment efficacy. In the last years, prostate-specific membrane antigen (PSMA)-PET/CT has become the reference standard examination for patients with advanced prostate cancer. Together with the rise of PSMA-PET, standardized frameworks for the reporting of image findings have been proposed, eg, the Prostate Cancer Molecular Imaging Standardized Evaluation (PROMISE) and the structured reporting system for PSMA targeted PET imaging (PSMA-RADS) framework. Therefore, recent evidence on PSMA-PET derived tumor volume as useful a biomarker for outcome prognostication and related frameworks will be discussed in the article. The PROMISE framework recommends quantifying the tumor volume per-organ system, which accounts for the fact that the location of the metastases greatly influence its biological aggressiveness. In addition, changes in PSMA-PET derived tumor volume have been shown to be promising biomarkers for response assessment. Limitations of PSMA-PET will also be discussed because the tumor volume might not always be suited for response assessment. As a pitfall of PSMA-based systems, decreasing PSMA-expression might erroneously be interpreted as response to therapy. Also, especially for patients with limited disease, the tumor volume might not be ideal for response assessment. Therefore, various frameworks have been introduced to objectively measure response to therapy with PSMA-PET. Amongst these, the PSMA-PET progression (PPP) criteria and the response evaluation criteria in PSMA (RECIP) are optimized for earlier and later phenotypes of advanced prostate cancer, respectively. Variables needed to determine PPP or RECIP outcome on PSMA-PET are recorded under the umbrella of PROMISE recommendations. In this article, various reporting and response assessment frameworks are explained and discussed. Also, recent evidence for the relevance of PSMA-PET biomarkers for clinical management and outcome prognostication are shown.

Tata Memorial Centre Evidence Based Use of Nuclear medicine diagnostic and treatment modalities in cancer

ABSTRACT

PET/CT and radioisotope therapy are diagnostic and therapeutic arms of Nuclear Medicine, respectively. With the emergence of better technology, PET/CT has become an accessible modality. Diagnostic tracers exploring disease-specific targets has led the clinicians to look beyond FDG PET. Moreover, with the emergence of theranostic pairs of radiopharmaceuticals, radioisotope therapy is gradually making it's way into treatment algorithm of common cancers in India. We therefore would like to discuss in detail the updates in PET/CT imaging and radionuclide therapy and generate a consensus-driven evidence based document which would guide the practitioners of Oncology.

How to Report PSMA PET

Prostate cancer (PCa) is the most common cancer diagnosed in men in most developed countries and a leading cause of cancer-related morbidity and mortality. Prostate-specific membrane antigen positron emission tomography (PSMA-PET) has become a valuable tool in the staging and assessment of disease recurrence in PCa, and more recently for assessment for treatment eligibility to PSMA radioligand therapy (RLT). Harmonization of PSMA-PET interpretation and synoptic reports are needed to communicate concisely and reproducibly PSMA-PET/CT to referring physicians and to support clinician therapeutic management decisions in various stages of the disease. Uniform image interpretation is also important to provide comparable data between clinical trials and to translate such data from research to daily practice. This review provides an overview of the value of PSMA-PET across the different clinical stages of PCa, discusses published reporting criteria for PSMA-PET, identifies pitfalls in reporting PSMA, and provides recommendations for synoptic reports.

PSMA PET/CT for Response Assessment and Overall Survival Prediction in Patients with Metastatic Castration-Resistant Prostate Cancer Treated with Androgen Receptor Pathway Inhibitors

We aimed to evaluate the role of prostate-specific membrane antigen (PSMA) PET/CT for response assessment and outcome prediction in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with androgen receptor pathway inhibitors (ARPIs), including abiraterone acetate or enzalutamide. Methods: We retrospectively analyzed 30 ARPI-treated mCRPC patients who underwent 68Ga-PSMA-11 PET/CT within 8 wk before (baseline) and 12 ± 4 wk after treatment initiation. Total PSMA tumor volume was calculated using the fixed threshold method (SUV ≥ 3). Patients were categorized as PSMA responders (PSMA-Rs) or PSMA nonresponders (PSMA-NRs) on the basis of both European Association of Urology/European Association of Nuclear Medicine (EAU/EANM) criteria and Response Evaluation Criteria in PSMA PET/CT (RECIP) 1.0. PSMA-R included patients with a complete response, a partial response, or stable disease, and PSMA-NR included those with progressive disease. On the basis of prostate-specific antigen (PSA), patients were classified as biochemical responders if PSA decreased by at least 50% and as nonresponders if it did not. The Φ-coefficient was used to evaluate the correlation of PSMA- and PSA-based responses. Survival analysis was performed using the Cox regression hazard model and the Kaplan-Meier method. Predictive accuracy was tested for both response criteria. Results: On the basis of PSMA PET/CT, 13 (43%) patients were PSMA-NR according to the EAU/EANM criteria and 11 (37%) patients were PSMA-NR according to RECIP 1.0. Significant correlations were observed between PSMA- and PSA-based responses for both criteria (Φ = 0.79 and 0.66, respectively). After a median follow-up of 25 mo (interquartile range, 21-43 mo), the median overall survival was significantly longer for PSMA-R than PSMA-NR (54 vs. 22 mo) for both the EAU/EANM criteria and RECIP 1.0, with hazard ratios of 6.9 (95% CI, 1.9-26; P = 0.004) and 5.6 (95% CI, 1.69-18.26, P = 0.005), respectively. No significant difference in predictive accuracy was found between the 2 criteria (C-index, 0.79 vs. 0.76, respectively, P = 0.54). Flare phenomena at the second PSMA PET study were not observed in our cohort. Conclusion: Our results demonstrate that PSMA PET/CT is a valuable imaging biomarker for response assessment and overall survival prediction when performed at 3 mo after ARPI treatment initiation in mCRPC patients. Both proposed PSMA response criteria (EAU/EANM and RECIP 1.0) seem to perform equally well. No PSMA flare was observed. Prospective validation of these findings is strongly needed.

From FDG and beyond: the evolving potential of nuclear medicine

The radiopharmaceutical 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) has been dominantly used in positron emission tomography (PET) scans for over 20 years, and due to its vast utility its applications have expanded and are continuing to expand into oncology, neurology, cardiology, and infectious/inflammatory diseases. More recently, the addition of artificial intelligence (AI) has enhanced nuclear medicine diagnosis and imaging with FDG-PET, and new radiopharmaceuticals such as prostate-specific membrane antigen (PSMA) and fibroblast activation protein inhibitor (FAPI) have emerged. Nuclear medicine therapy using agents such as [177Lu]-dotatate surpasses conventional treatments in terms of efficacy and side effects. This article reviews recently established evidence of FDG and non-FDG drugs and anticipates the future trajectory of nuclear medicine.