Membrane Antigen Positron Emission Tomography Research Articles

Nadir Prostate-specific Antigen as an Independent Predictor of Survival Outcomes: A Post Hoc Analysis of the PROSPER Randomized Clinical Trial.

This post hoc analysis of PROSPER evaluated the relationship between depth of PSA decline and clinical outcomes in enzalutamide-treated men with nonmetastatic castration-resistant prostate cancer. PROSPER was an international, randomized, double-blind, placebo-controlled, phase 3 trial that demonstrated significantly improved metastasis-free survival and overall survival with androgen deprivation therapy plus enzalutamide vs placebo. A total of 905 enzalutamide-treated men were included in this post hoc analysis. Metastasis-free survival (primary endpoint) and overall survival (secondary endpoint) were evaluated for 4 mutually exclusive subgroups defined by PSA decline: <50% (reference); ≥50% to <90%; ≥90%, nadir ≥0.2 ng/mL; and ≥90%, nadir <0.2 ng/mL. Medians and 95% confidence intervals were determined using a 12-month landmark analysis; hazard ratios and P values were based on an unstratified Cox proportional analysis model. In enzalutamide-treated men, PSA declines of <50%, ≥50% to <90%, ≥90% with nadir ≥0.2 ng/mL, and ≥90% with nadir <0.2 ng/mL were associated with median metastasis-free survival in months (95% confidence intervals) of 22.1 (14.8-not reached), 34.2 (29.4-not reached), 36.6 (33.4-not reached), and not reached, respectively, and overall survival in months (95% confidence intervals) of 40.8 (31.7-44.9), 54.4 (49.0-67.0), 64.3 (63.4-not reached), and not reached, respectively. There was a statistically significant correlation between greater depth of PSA decline and improved clinical outcomes, suggesting a previously underappreciated relationship between changes in PSA levels and clinical outcomes in nonmetastatic castration-resistant prostate cancer.

Irreversible electroporation for prostate cancer using PSMA PET-CT.

To demonstrate the clinical usefulness of prostate-specific membrane antigen (PSMA) positron emission tomography (PET) computerized tomography (CT) for irreversible electroporation (IRE) in prostate cancer patients. From January to May 2021, 17 men were diagnosed with localized prostate cancer through preoperative mpMRI and [18F] florastamin PSMA PET-CT imaging, followed by transperineal MRI-ultrasound fusion-guided biopsy. The patients underwent IRE focal therapy at the target lesions under general anesthesia. To evaluate the treatment outcome, serum prostate-specific antigen (PSA) levels were followed up in the 1st, 3rd, 6th, 9th, 12th months, and mpMRI was taken in the 1st and 12th months, followed by MR fusion biopsy in the 12th month post-IRE. The mean age of the patients was 66.1±9.3 with a median PSA of 7.5ng/ml. After the treatment, PSA nadir was 4.06±3.4, and 11 (64.7%) achieved decline of PSA more than 50% from the baseline. Rate of negative biopsy for prostate cancer is 88% (15/17) at 12monthsMR fusion biopsy after the IRE treatment. Among the relapsed cases, 1 (6.9%) patient recurred at margin of treated area, and 1 (6.9%) patient was from outfield recurrence. When excluding initial four patients, none of the patients had cancer recur. When treating with IRE focal therapy, PSMA-PET CT is a potentially valuable diagnostic approach for localizing prostate cancer; it supports the detection of lesions with conventional mpMRI, enabling to perform the procedure more completely.

Feasibility of biology-guided radiotherapy for metastatic renal cell carcinoma driven by PSMA PET imaging

BackgroundBiology-guided radiotherapy (BgRT) is a novel treatment where the detection of positron emission originating from a volume called the biological tracking zone (BTZ) initiates dose delivery. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is a novel imaging technique that may improve patient selection for metastasis-directed therapy in renal cell carcinoma (RCC). This study aims to determine the feasibility of BgRT treatment for RCC. Material and methodsAll consecutive patients that underwent PSMA PET/CT scan for RCC staging at our institution between 2014 and 2020 were retrospectively considered for inclusion. GTVs were contoured on the CT component of the PET/CT scan. The tumor-to-background ratio was quantified from the normalized standardized uptake value (nSUV), defined as the ratio between SUVmax inside the GTV and SUVmean inside the margin expansion. Tumors were classified suitable for BgRT if (1) nSUV was greater or equal to an nSUV threshold and (2) if the BTZ was free of any PET-avid region other than the tumor. ResultsOut of this cohort of 83 patients, 47 had metastatic RCC and were included in this study. In total, 136 tumors were delineated, 1 to 22 tumors per patient, mostly in lung (40%). Using a margin expansion of 5 mm/10 mm/20 mm and nSUV threshold = 3, 66%/63%/41% of tumors were suitable for BgRT treatment. Uptake originating from another tumor, the kidney, or the liver was typically inside the BTZ in tumors judged unsuitable for BgRT. ConclusionsMore than 60% of tumors were found to be suitable for BgRT in this cohort of patients with RCC. However, the proximity of PET-avid organs such as the liver or the kidney may affect BgRT delivery.

Clinical outcomes after utilization of PSMA PET scans in patients with biochemical recurrent prostate cancer.

57 Background: The optimal management of biochemical recurrent prostate cancer (BCR) remains unknown. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) scans can visualize micrometastatic disease, thus expanding treatment options for BCR from observation or androgen deprivation therapy (ADT) to potentially include metastasis-directed radiation (XRT) or next-generation hormonal agents (NHA). We aimed to describe how BCR patients were managed after PSMA PET scans and their clinical outcomes. Methods: We performed a retrospective chart review of 262 patients from the University of Michigan’s PSMA PET scan database (825 patients with scans 2017–2021). Patients who received maximal local therapy (defined as XRT alone n=199 or surgery + XRT n=63) are presented. Only patients with BCR and a minimum of 1 year follow-up after scans were included. Baseline patient and tumor characteristics, PSMA PET scan results, first and subsequent therapy delivered after PSMA PET, and prostate-specific antigen (PSA) and standard imaging results post PSMA PET were annotated. Primary endpoint is time from first post-scan therapy (within 6 months of scan) to subsequent therapy. Secondary outcomes include probability of no subsequent therapy in 1 year based on first post-scan therapy and PSMA scan findings and PSMA PET findings and association with Gleason score, PSA at BCR, and time from diagnosis to PSMA scan. Results: Of 262 patients with maximal local therapy, 115 met inclusion criteria. Primary definitive treatment was XRT alone in 58% and surgery + XRT in 42%. Median PSA at time of scan was 4.4 ng/mL, and PSMA PET was positive in 87%. First therapy rendered after PSMA PET included 15% no therapy, 26% XRT only, 28% systemic therapy only (ADT +/- NHA), 27% combination therapy (XRT +/- systemic), and 4% other. Subsequent therapy was given in 26%. The median time from first to subsequent therapy was 41 months in patients who received XRT alone as first therapy and not reached for those with combination XRT + ADT. None of the 33 treated with combination therapy required subsequent therapy in 1 year. Remainder of analyses incomplete due to small sample sizes. Results to be updated by time of symposium. Conclusions: This observational study characterizes longer term clinical outcomes in patients with BCR who undergo various therapies after PSMA PET scans. Data may inform current decision making while prospective clinical trial data is awaited.

Radical Prostatectomy without Prior Biopsy in Patients with High Suspicion of Prostate Cancer Based on Multiparametric Magnetic Resonance Imaging and Prostate-Specific Membrane Antigen Positron Emission Tomography: A Prospective Cohort Study

Modern risk stratification of prostate cancer (PCa) allows for prediction of advanced disease with a high level of certainty. We aimed to evaluate a prospective series of patients undergoing radical prostatectomy without prior biopsy based solely on clinical criteria and imaging results. The patients were divided into three groups. Group 1 included 27 patients with: (i) suspicious digital rectal examination, (ii) PSA ≥ 10 ng/mL, (iii) PI-RADS 4/5 on mpMRI, and (iv) high suspicion of PCa on PSMA-PET. Group 2 included six patients who fulfilled criteria i, ii, and iii but did not undergo PSMA-PET imaging. Group 3 included 17 patients with at least one clinical (i or ii) and one imaging (iii or iv) criterion. All of the patients were diagnosed with PCa. Comparison of Group 1 and 2 versus Group 3 showed a significantly higher ratio of locally advanced PCa for Groups 1 and 2 compared to Group 3 (60.6% versus 11.8%, p = 0.005, respectively). Similarly, these patients displayed a significantly higher ratio of aggressive PCa (ISUP grade > 2: 66.7% versus 23.5%, p = 0.027, respectively) and tumor infiltration (median tumor infiltration: 32.5% vs. 15%, p = 0.001, respectively) in the final specimen compared to Group 3. In conclusion, we have shown that radical prostatectomy without prior biopsy is safe in terms of the diagnosis of clinically significant PCa when proper preoperative risk stratification involving mpMRI and PSMA-PET imaging is applied.

Mask R-CNN assisted 2.5D object detection pipeline of 68Ga-PSMA-11 PET/CT-positive metastatic pelvic lymph node after radical prostatectomy from solely CT imaging

Prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) is a molecular and functional imaging modality with better restaging accuracy over conventional imaging for detecting prostate cancer in men suspected of lymph node (LN) progression after definitive therapy. However, the availability of PSMA PET/CT is limited in both low-resource settings and for repeating imaging surveillance. In contrast, CT is widely available, cost-effective, and routinely performed as part of patient follow-up or radiotherapy workflow. Compared with the molecular activities, the morphological and texture changes of subclinical LNs in CT are subtle, making manual detection of positive LNs infeasible. Instead, we harness the power of artificial intelligence for automated LN detection on CT. We examined 68Ga-PSMA-11 PET/CT images from 88 patients (including 739 PSMA PET/CT-positive pelvic LNs) who experienced a biochemical recurrence after radical prostatectomy and presented for salvage radiotherapy with prostate-specific antigen < 1 ng/mL. Scans were divided into a training set (nPatient = 52, nNode = 400), a validation set (nPatient = 18, nNode = 143), and a test set (nPatient = 18, nNodes = 196). Using PSMA PET/CT as the ground truth and consensus pelvic LN clinical target volumes as search regions, a 2.5-dimensional (2.5D) Mask R-CNN based object detection framework was trained. The entire framework contained whole slice imaging pretraining, masked-out region fine-tuning, prediction post-processing, and “window bagging”. Following an additional preprocessing step—pelvic LN clinical target volume extraction, our pipeline located positive pelvic LNs solely based on CT scans. Our pipeline could achieve a sensitivity of 83.351%, specificity of 58.621% out of 196 positive pelvic LNs from 18 patients in the test set, of which most of the false positives can be post-removable by radiologists. Our tool may aid CT-based detection of pelvic LN metastasis and triage patients most unlikely to benefit from the PSMA PET/CT scan.

Gene’s expression underpinning the divergent predictive value of [18F]F-fluorodeoxyglucose and prostate-specific membrane antigen positron emission tomography in primary prostate cancer: a bioinformatic and experimental study

BackgroundPositron Emission Tomography (PET) imaging with Prostate-Specific Membrane Antigen (PSMA) and Fluorodeoxyglucose (FDG) represent promising biomarkers for risk-stratification of Prostate Cancer (PCa). We verified whether the expression of genes encoding for PSMA and enzymes regulating FDG cellular uptake are independent and additive prognosticators in PCa.MethodsmRNA expression of genes involved in glucose metabolism and PSMA regulation obtained from primary PCa specimens were retrieved from open-source databases and analyzed using an integrative bioinformatics approach. Machine Learning (ML) techniques were used to create predictive Progression-Free Survival (PFS) models. Cellular models of primary PCa with different aggressiveness were used to compare [18F]F-PSMA-1007 and [18F]F-FDG uptake kinetics in vitro. Confocal microscopy, immunofluorescence staining, and quantification analyses were performed to assess the intracellular and cellular membrane PSMA expression.ResultsML analyses identified a predictive functional network involving four glucose metabolism-related genes: ALDOB, CTH, PARP2, and SLC2A4. By contrast, FOLH1 expression (encoding for PSMA) did not provide any additive predictive value to the model. At a cellular level, the increase in proliferation rate and migratory potential by primary PCa cells was associated with enhanced FDG uptake and decreased PSMA retention (paralleled by the preferential intracellular localization).ConclusionsThe overexpression of a functional network involving four glucose metabolism-related genes identifies a higher risk of disease progression since the earliest phases of PCa, in agreement with the acknowledged prognostic value of FDG PET imaging. By contrast, the prognostic value of PSMA PET imaging is independent of the expression of its encoding gene FOLH1. Instead, it is influenced by the protein docking to the cell membrane, regulating its accessibility to tracer binding.

Prostate Cancer: Management of Biochemical Recurrence after Surgery.

Radical prostatectomy (RP) is one of the primary treatment options for localised prostate cancer (PCa). Despite its curative intent, 1/3 of patients will experience biochemical recurrence (BCR) during follow-up. Experts have devoted efforts to associate the influence of each individual factor with the risk of BCR to select the optimal treatment for each patient. Optimal management must aim to find a balance between delaying the onset of metastatic disease and overtreating an indolent disease with treatments that can affect quality of life of the patients. Thus far, effective treatment options for men with BCR remain controversial in terms of ideal treatment timing (adjuvant vs. salvage), radiotherapy (RT) fields and doses, selection and duration of systemic therapy and potential synergies between treatments and their therapeutic sequencing. Next-generation imaging techniques, such as Prostate-Specific Membrane Antigen Positron Emission Tomography, are used for early detection of disease progression and exact site of recurrence or progression, thereby enhancing decision making for future disease management. In this review, we evaluate available evidence of controversial topics regarding BCR after RP and explore future directions, such as prognostic and/or predictive factors of response, genetic panels, second-generation hormone treatments, ultra-hypofractionated RT and ongoing clinical trials in this clinical scenario.

68Ga-PSMA PET-CT and PSMA score affecting therapeutic decision-making in high-risk prostatic carcinoma.

This research study was conducted to evaluate the impact of (68Ga)-tagged prostatic-specific membrane antigen (68Ga-PSMA) positron emission tomography and computed tomography (PET-CT), compare its role with conventional radiology in early staging of high-risk prostate cancer, and calculate the PSMA score evaluating its usefulness in 68Ga-PSMA PET-CT reporting in our patient population. 68Ga-PSMA PET-CT of 65 high-risk cases of prostate cancer was performed for staging purpo-ses. Any change in disease stage was noted after 68Ga-PSMA PET-CT findings and PSMA score leading to a change in the management plan. Change in disease stage post-PSMA imaging was seen in 39% cases, high PSMA score (03) was noted in > 80% of upstaged cases, while low score (0) and (1) was seen in 65% and 35% down-staged individuals, respectively. Change in therapeutic decision-making was observed in 32% (21) of patients. 68Ga-PSMA PET-CT scans have a significant influence on the planned clinical management of high-risk prostate cancer patients; hence, they can be utilized as a replacement for radiological imaging tools, particularly in the detection of pelvic nodal and distant metastatic disease. PSMA score can be considered as an effective tool in standardized reporting of 68Ga-PSMA imaging.

Can 18F-PSMA-7Q PET/CT replace prostate biopsy for the diagnosis of prostate cancer?-A single-center retrospective study.

Of the currently available prostate-specific membrane antigen (PSMA) positron emission tomography (PET) tracers, although 68Ga-PSMA-11 and 18F-DCFPyL have been approved by the US Food and Drug Administration (FDA), both tracers are excreted rapidly through the urinary tract, resulting in strong accumulation in the bladder and blurring the prostate.18F-PSMA-7Q is a novel quinoline-containing PSMA PET tracer developed by our team, which is primarily excreted through the liver. It can reduce the incidence of urine-induced false-positives in the prostate. We aimed to explore the diagnostic efficacy of 18F-PSMA-7Q PET/computed tomography (CT), and when 18F-PSMA-7Q PET/CT can be used instead of prostate biopsy to diagnose prostate cancer. Patients who underwent 18F-PSMA-7Q PET/CT for prostate cancer staging or prostate biopsy guidance at our institution between July 2020 and December 2021 were retrospectively enrolled. Molecular imaging PSMA (miPSMA) scores were assigned for intra-prostatic lesions according to the Prostate Cancer Molecular Imaging Standardized Evaluation (PROMISE) criteria, and the diagnostic efficacy of 18F-PSMA-7Q PET/CT for different miPSMA scores was evaluated using pathological diagnosis as the gold standard. Of the 125 enrolled patients, 101 had prostate cancer, and 24 had prostatic hyperplasia or prostatitis. miPSMA ≥2 was the optimal diagnostic threshold, and area under curve (AUC) was 0.948, the sensitivity and specificity were 91.1% and 83.0%. The prostate cancer detection rates of 18F-PSMA-7Q PET/CT were 14.3% (3/21), 60.0% (6/10), 96.7% (58/60), and 100% (34/34) for patients with miPSMA scores of 0, 1, 2, and 3, respectively. There was no significant difference in the detection rate of prostate cancer between groups with miPSMA scores of 2 and 3, but there were significant differences between any other 2 groups. The prostate cancer detection rate of 18F-PSMA-7Q PET/CT was high for lesions with greater miPSMA scores of 2 and 3. For patients with a high miPSMA score, particularly those with a miPSMA score of 3, prostate biopsy can be omitted and prostate cancer-related treatment can be considered.

The Impact of PSMA-PET on Oncologic Control in Prostate Cancer Patients Who Experienced PSA Persistence or Recurrence.

Background: Prostate Specific Membrane Antigen-Positron Emission Tomography (PSMA-PET) is currently recommended to restage prostate cancer (PCa) and to guide the delivery of salvage treatments. We aim to evaluate the oncologic outcomes of patients with recurrent PCa who received PSMA-PET. Methods: 324 hormone-sensitive PCa with PSA relapse after radical prostatectomy who underwent PSMA-PET in three high-volume European Centres. Patients have been stratified as pre-salvage who never received salvage treatments (n = 134), and post-salvage, including patients who received previous salvage therapies (n = 190). Patients with oligorecurrent (≤3 lesions), PSMA-positive disease underwent PSMA-directed treatments: salvage radiotherapy (sRT) or Metastases-directed therapy (MDT). Patients with polirecurrent (>3 lesions) PSMA-positive disease were treated with systemic therapy. Patients with negative PSMA-PET were treated with sRT or systemic therapies or observation. The primary outcome of the study was Progression-free survival (PFS). Secondary outcomes were: Metastases-free survival (MFS) and Castration Resistant Pca free survival (CRPC-FS). Results: median follow up was 23 months. In the pre-salvage setting, the PFS, MFS and CRPC-FS estimates at 3 years were 66.2% vs. 38.9%, 95.2% vs. 73.7% and 94.9% vs. 93.1% in patients with negative vs. positive PSMA-PET, respectively (all p ≥ 0.2). In the post-salvage setting, the PFS, MFS and CRPC-FS estimates at 3 years were 59.5% vs. 29.1%, 92.7% vs. 65.1% and 98.8% vs. 88.8% in patients with negative vs. positive PSMA-PET, respectively (all p ≤ 0.01). At multivariable analyses, a positive PSMA-PET was an independent predictor of progression (HR = 2.15) and metastatic disease (HR 2.37; all p ≤ 0.03). Conclusion: PSMA-PET in recurrent PCa detects the site of recurrence guiding salvage treatments and has a prognostic role in patients who received previous salvage treatments.

Deep learning and radiomics framework for PSMA-RADS classification of prostate cancer on PSMA PET

BackgroundAccurate classification of sites of interest on prostate-specific membrane antigen (PSMA) positron emission tomography (PET) images is an important diagnostic requirement for the differentiation of prostate cancer (PCa) from foci of physiologic uptake. We developed a deep learning and radiomics framework to perform lesion-level and patient-level classification on PSMA PET images of patients with PCa.MethodsThis was an IRB-approved, HIPAA-compliant, retrospective study. Lesions on [18F]DCFPyL PET/CT scans were assigned to PSMA reporting and data system (PSMA-RADS) categories and randomly partitioned into training, validation, and test sets. The framework extracted image features, radiomic features, and tissue type information from a cropped PET image slice containing a lesion and performed PSMA-RADS and PCa classification. Performance was evaluated by assessing the area under the receiver operating characteristic curve (AUROC). A t-distributed stochastic neighbor embedding (t-SNE) analysis was performed. Confidence and probability scores were measured. Statistical significance was determined using a two-tailed t test.ResultsPSMA PET scans from 267 men with PCa had 3794 lesions assigned to PSMA-RADS categories. The framework yielded AUROC values of 0.87 and 0.90 for lesion-level and patient-level PSMA-RADS classification, respectively, on the test set. The framework yielded AUROC values of 0.92 and 0.85 for lesion-level and patient-level PCa classification, respectively, on the test set. A t-SNE analysis revealed learned relationships between the PSMA-RADS categories and disease findings. Mean confidence scores reflected the expected accuracy and were significantly higher for correct predictions than for incorrect predictions (P < 0.05). Measured probability scores reflected the likelihood of PCa consistent with the PSMA-RADS framework.ConclusionThe framework provided lesion-level and patient-level PSMA-RADS and PCa classification on PSMA PET images. The framework was interpretable and provided confidence and probability scores that may assist physicians in making more informed clinical decisions.

Management of Patients with Recurrent and Metachronous Oligometastatic Prostate Cancer in the Era of PSMA PET.

Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) scans have higher sensitivity and specificity for detecting lymph nodes or metastatic disease relative to conventional imaging in prostate cancer staging. Since its FDA approval and incorporation into treatment guidelines, the use of PSMA PET has increased in patients undergoing initial staging, those with recurrence after initial definitive treatment, and patients with metastatic disease. Although the early detection of metastatic lesions is changing disease management, it is unclear whether this impact on management translates into clinical benefit. This review will summarize evidence pertaining to the change in patient management due to PSMA PET use and will discuss the implications of PSMA PET on treatment decisions in prostate cancer, particularly in the settings of biochemical recurrence and metachronous oligometastatic disease.

Synchronous vs independent reading of prostate-specific membrane antigen positron emission tomography (PSMA-PET) and magnetic resonance imaging (MRI) to improve diagnosis of prostate cancer.

To identify whether synchronous reading of multiparametric magnetic resonance imaging (mpMRI) and 68 Ga-PSMA-11 positron emission tomography (PET)/computed tomography (prostate-specific membrane antigen [PSMA-PET]) images can improve diagnostic performance and certainty compared with mpMRI/PSMA-PET reported independently and synthesized, while also assessing concordance between imaging modalities and agreement with histopathology. This was a retrospective analysis of 100 patients randomly selected from the PRIMARY trial, a prospective Phase II multicentre imaging trial. Three dual-trained radiologist/nuclear medicine physicians re-reported the mpMRI and PSMA-PET both independently and synchronously for the same patients in random order, blinded to previous results. Diagnostic performance was assessed for mpMRI/PSMA-PET images read synchronously or independently and then synthesized. Agreement between imaging results and histopathology was examined. 'Concordance' between imaging modalities was defined as overlapping lesions. Reporting certainty was evaluated by the individual reporters for each modality. International Society of Urological Pathology Grade Group ≥2 cancer was present in 60% of patients on biopsy. Synchronous reading of mpMRI/PSMA-PET increased sensitivity compared to mpMRI or PSMA-PET alone (93% vs 80% vs 88%, respectively), although specificity was not improved (63% vs 58% vs 78%, respectively). No significant difference in diagnostic performance was noted between mpMRI/PSMA-PET read synchronously and mpMRI or PSMA-PET reported independently and then synthesized. Most patients had concordant imaging (60%), while others had discordant lesions only (28%) or a mixture (concordant and discordant lesions; 12%). When mpMRI/PSMA-PET findings were concordant and positive, 95% of patients had clinically significant prostate cancer (csPCa). When PSMA-PET alone was compared to synchronous PSMA-PET/MRI reads, there was an improvement in reader certainty in 20% of scans. Synchronous mpMRI/PSMA-PET reading improves reader certainty and sensitivity for csPCa compared to mpMRI or PSMA-PET alone. However, synthesizing the results of independently read PSMA-PET and mpMRI reports provided similar diagnostic performance to synchronous PSMA-PET/MRI reads. This may provide greater flexibility for urologists in terms of referral patterns, reducing healthcare system costs and improving efficiencies in prostate cancer diagnosis.

Management of patients with advanced prostate cancer in Japan: 'real-world' consideration of the results from the Advanced Prostate Cancer Consensus Conference.

A multidisciplinary approach is necessary to manage advanced prostate cancer. The Advanced Prostate Cancer Consensus Conference (APCCC) in 2019 provided a practical guide to help clinicians consider therapeutic options in controversial areas, but healthcare systems vary across the world. At the 109th annual meeting of the Japanese Urological Association in December 2021, Japanese urologists voted on the questions in the APCCC 2019 guidelines regarding prostate-specific membrane antigen-positron emission tomography (PSMA-PET), management of oligometastatic prostate cancer, management of nonmetastatic castration-resistant prostate cancer (CRPC), management of a primary tumor in metastatic settings, systemic treatment of newly diagnosed metastatic castration-sensitive prostate cancer (CSPC), management of metastatic CRPC (mCRPC), and tumor genomic testing. We summarize the "real-world" status of the management of advanced prostate cancer in Japan. Several differences were noted in the management of advanced prostate cancer between Japanese urologists and the APCCC 2019 guidelines. Many Japanese urologists chose conventional imaging modalities for detecting metastasis instead of PSMA-PET. More Japanese urologists prefer androgen-deprivation therapy (ADT) alone in the management of low-volume metastatic CSPC than the APCCC panelists do, In the management of M0 CRPC, darolutamide and enzalutamide were chosen more by Japanese urologists than by the voters at the APCCC 2019. Bicalutamide remains one of the options for the management of mCRPC in Japan. More Japanese urologists do not recommend microsatellite instability (MSI) and BRCA1/2 tests than the voters at the APCCC 2019. Clinical evidence in Japan should be collected to address these discrepancies.

Micro-Ultrasound in the Diagnosis and Staging of Prostate and Bladder Cancer: A Comprehensive Review.

Background and Objectives: Multiparametric magnetic resonance imaging (mpMRI) of the prostate and prostate-specific membrane antigen positron emission tomography (PSMA PET) are some examples of how the advancement of imaging techniques have revolutionized the diagnosis, staging, and consequently management of patients with prostate cancer (PCa). Although with less striking results, novel radiological modalities have also been proposed for bladder cancer (BCa) in recent years. Micro-ultrasound (MUS) is an imaging examination characterized by high real-time spatial resolution, recently introduced in the urological field. This article aimed to describe the current evidence regarding the application of MUS for the diagnosis and staging of PCa and BCa. Materials and Methods: We designed a narrative review. A comprehensive search in the MEDLINE, Scopus, and Cochrane Library databases was performed. Articles in English-language and published until July 2022 were deemed eligible. Retrospective and prospective primary clinical studies, as well as meta-analyses, were included. Results: MUS-guided prostate biopsy showed high sensitivity (0.91, 95% CI, 0.79-0.97) in the diagnosis of clinically significant PCa (csPCa). It was associated with a higher detection rate of csPCa than a systematic biopsy (1.18, 95% CI 0.83-1.68). No significant difference was found between MUS and mpMRI-guided biopsy in the total detection of PCa (p = 0.89) and in the detection of Grade Groups ≥ 2 (p = 0.92). The use of MUS to distinguish between non-muscle-invasive and muscle-invasive BCa was described, highlighting an up-staging with MUS only in a minority of cases (28.6%). Conclusions: Promising findings have emerged regarding the feasibility and accuracy of MUS in the diagnosis and staging of PCa and BCa. However, the available evidence is limited and should be considered preliminary.

Development of a CT-Based Auto-Segmentation Model for Prostate-Specific Membrane Antigen (PSMA) Positron Emission Tomography-Delineated Tubarial Glands.

Modern inverse planning radiotherapy techniques allow for organs at risk (OARs) to evade radiation doses that they would have been subjected to with earlier techniques. The extent to which patient outcomes may be improved using these techniques depends on the delineation accuracy of target volumes and OARs on medical imagesas well asclinical dose constraints applied to regions of interest (ROIs). The recent discovery of bilateral "tubarial" salivary glands, which were found in the nasopharynx using prostate-specific membrane antigen (PSMA) positron emission tomography (PET), raises concerns over how dose to this region might affect patient outcomes. The dose response of the major salivary glands is known to be variable, and it is possible that the dose in tubarial glands constitutes a missing variable in the optimization of head and neck (HN) radiotherapy plans. A necessary first step towardconducting clinical studies that include the tubarial glands in plan optimization is to develop methods for delineating these glands without the use of PSMA PET images, as their acquisition is not considered a part of the standard of care for HN patients. In this study, we develop an open-source program, Organogenesis, for the auto-segmentation of tubarial glands using only computed tomography (CT) images. A predictive model is trained using contours derived from PSMA PET images, allowing for accurate delineation of tubarial glands, which cannot be manually contoured using CT only. Organogenesis provides a predictive model for tubarial glands that can be iteratively improved on with additional data, creating a viable pathway to clinical studies that can assess the importance of incorporating tubarial glands into HN radiotherapy plan optimization.

Prostate-Specific Membrane Antigen PET Response Associates with Metastasis-Free Survival Following Stereotactic Ablative Radiation Therapy in Oligometastatic Castration-Sensitive Prostate Cancer

<h3>Purpose/Objective(s)</h3> Emerging data suggest metastasis-directed therapy (MDT) improves outcomes in patients with oligometastatic castration-sensitive prostate cancer (omCSPC). Prostate-specific membrane antigen positron emission tomography (PSMA-PET/CT) can detect occult metastatic disease and has been proposed as a biomarker for treatment response. Herein we identify and validate a PSMA-PET biomarker for clinical outcomes following MDT in omCSPC. <h3>Materials/Methods</h3> This was an international multi-institutional retrospective study of two independent cohorts of omCSPC, defined as ≤3 lesions, treated with metastasis-directed stereotactic ablative radiation therapy (SABR). Patients underwent PSMA-PET/CT prior to and 3-6 months after treatment. Pre- and post-SABR PSMA-PET/CT standardized uptake value (SUV) was measured for all lesions and PSMA response defined discretely using a cutpoint of ≥ 30% decrease in SUV_max. PSMA-PET response was correlated with lesion local control (LLC), and metastasis-free survival (MFS), defined per ICECaP working group by a new metastasis on conventional imaging alone (not including pelvic lymph node metastases) or death. <h3>Results</h3> A total of 131 patients (discovery n=35, validation n=96) with 261 treated metastases were included in the analysis, with median follow-up of 29 months (IQR 18.5-41.3). Following SABR, 78.4% of lesions experienced a partial or complete PSMA response. Multivariable analysis demonstrated SUV response significantly associated with improved LLC (HR=0.10, 95%CI 0.04-0.26; p<0.01). Patients with PSMA response in all lesions experienced significantly better MFS (HR=0.37, 95%CI 0.21-0.65; p<0.01) compared to their counterparts, and this maintained significance within both the discovery (p=0.02) and validation (p<0.01) cohorts. <h3>Conclusion</h3> Following SABR, PSMA-PET response is a robust and externally validated radiographic biomarker for MFS in omCSPC. This approach holds promise for guiding clinical management of omCSPC and should be validated as an early response indicator biomarker in localized and other advanced states of prostate cancer.

Can Perirectal Spacing Help Reduce GI Toxicity in Patients Undergoing Post-Prostatectomy Radiotherapy?

<h3>Purpose/Objective(s)</h3> To report single institutional feasibility of recto-vesical hyaluronic acid or hydrogel spacer insertion for patients undergoing post prostatectomy radiotherapy (PPRT). <h3>Materials/Methods</h3> Spacer insertion was considered in patients referred for PPRT following an intra or interfascial radical prostatectomy who had no radiological evidence of local recurrence (based on prostate specific membrane antigen positron emission tomography). The spacer was inserted into the perirectal fat between the bladder and anterior rectal wall using a transperineal approach under transrectal ultrasound guidance. Two gold seed fiducial markers were also inserted at the level of the vesico-urethral anastomosis for image guided radiation therapy as per institutional practice. Pre and post spacer computerized tomography planning scans, together with post spacer magnetic resonance imaging scans, were acquired for dosimetric comparison. The prostate bed clinical target volume (CTV) was delineated according to Australian guidelines and the CTV was uniformly expanded by 7mm to create the planning target volume (PTV). The prescribed dose to the prostate bed was 70.2Gy in 1.8 Gy fractions using volumetric arc radiation therapy. The PTV and rectal dosimetry for the two sets of planning scans (PTV 7mm/pre spacer and PTV 7mm/post spacer) were compared. <h3>Results</h3> Sixty-one patients were recruited between 9/18 to 10/21. Fifty-eight patients successfully underwent rectal spacer insertion without postoperative complications. We did not attempt spacer insertion in 3 patients as we were unable to hydrodissect the perirectal fat plane. Only 33 patients had pre spacer planning scans available for dosimetric comparison. The distance between the bladder and rectal wall was increased from ≤1mm to a median of 11mm (9-13) at its greatest extent. The rectal volume for all patients (N=61) receiving 42.2Gy (rV60%), 49.1Gy (rV70%), 56.2 Gy (rV80%), 63.2Gy (rV90%) and 70.2Gy (rV100%)] were 28.1%, 23%, 17.9%, 12.5% and 3.8% respectively. With spacing, a statistically significant reduction was seen on all rectal volume end points from rV60% to rV100% in the 33 patients with both pre and post planning scans (see Table 1). The median follow up was 10.5 months (3-31). The risk of any grade acute GI toxicity was 28% (grade 1 26% and grade 2 2%). The risk of late GI toxicity was 7% (all grade 1 proctitis). <h3>Conclusion</h3> More than 90% of our selected PPRT patients were able to achieve recto-vesical separation, with no surgical complications, resulting in a 43.7% reduction in rV90%. The reduction in acute and late grade 2 GI toxicity is of notable significance, albeit with short follow up. Table 1 Pre and Post Spacer Rectal Dosimetry

Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography–based Lymph Node Atlas for Salvage Radiotherapy in Patients with Recurrent Prostate Cancer: A Validation of the New NRG Oncology 2020 guideline

BackgroundApproximately 20–40% of patients with prostate cancer (PC) who undergo radical prostatectomy (RP) experience relapse, with the majority of these cases developing pelvic lymph node (LN) metastases. Taking new data from the prostate-specific membrane antigen (PSMA) positron emission tomography (PET) era into account, the Radiation Therapy Oncology Group (RTOG) 2009 contouring guideline for the pelvic LNs from 2009 was updated by the NRG Oncology group in 2020 (NRG 2020). ObjectiveTo evaluate and validate the updated NRG 2020 guideline with our established LN atlas. Design, setting, and participantsWe screened 1653 PSMA PET/computed tomography (CT) data sets for patients with biochemical relapse who underwent a PET scan between November 2012 and November 2017. After screening, we developed an LN atlas using data from 233 patients. Outcome measurements and statistical analysisWe evaluated LN overlap (OL) with the RTOG 2009 and NRG 2020 contouring guidelines. OL was defined as within (>90%), partly within (10–90%), or outside (<10%). Results and limitationsIn comparison to the RTOG 2009 guideline, 403 (52%), 134 (17%), and 241 (31%) of the LNs were not, were partly, or were fully covered within the overall group, respectively. By contrast, using the NRG 2020 guideline, 302 (39%), 190 (24%), and 286 (37%) of the LNs were not, were partly, or were fully covered, respectively (p < 0.001). Limitations include the retrospective design with missing data and no histopathological confirmation of the PET results. ConclusionsThe updated NRG 2020 contouring guideline improves coverage of the pelvic LNs in patients undergoing salvage radiation therapy. However, PET/CT should be considered whenever possible to ensure coverage of untypical LN spread. Patient summaryWe compared the 2009 and 2020 guidelines on the radiation area for the pelvis for patients with recurrent prostate cancer that has spread to lymph nodes. The newer guideline provides better coverage of pelvic lymph nodes than the older one and is useful in planning radiation therapy. However, a scan of the pelvis using the newest technique should be considered for individual patients to ensure coverage of untypical lymph nodes.