Optimal MRI sequences for 68Ga-PSMA-11 PET/MRI in evaluation of biochemically recurrent prostate cancer

PET/MRI in colorectal and anal cancers: an update

Positron emission tomography (PET) in the era of personalized medicine has a unique role in the management of oncological patients and offers several advantages over standard anatomical imaging. However, the role of molecular imaging in lower GI malignancies has historically been limited due to suboptimal anatomical evaluation on the accompanying CT, as well as significant physiological 18F-flurodeoxyglucose (FDG) uptake in the bowel. In the last decade, technological advancements have made whole-body FDG-PET/MRI a feasible alternative to PET/CT and MRI for lower GI malignancies. PET/MRI combines the advantages of molecular imaging with excellent soft tissue contrast resolution. Hence, it constitutes a unique opportunity to improve the imaging of these cancers. FDG-PET/MRI has a potential role in initial diagnosis, assessment of local treatment response, and evaluation for metastatic disease. In this article, we review the recent literature on FDG-PET/MRI for colorectal and anal cancers; provide an example whole-body FDG-PET/MRI protocol; highlight potential interpretive pitfalls; and provide recommendations on particular clinical scenarios in which FDG-PET/MRI is likely to be most beneficial for these cancer types.

International EANM-SNMMI-ISMRM consensus recommendation for PET/MRI in oncology

PREAMBLE

The Society of Nuclear Medicine and Molecular Imaging (SNMMI) is an international scientific and professional organization founded in 1954 to promote the science, technology, and practical application of nuclear medicine. The European Association of Nuclear Medicine (EANM) is a professional non-profit medical association that facilitates communication worldwide between individuals pursuing clinical and research excellence in nuclear medicine. The EANM was founded in 1985. The merged International Society for Magnetic Resonance in Medicine (ISMRM) is an international, nonprofit, scientific association whose purpose is to promote communication, research, development, and applications in the field of magnetic resonance in medicine and biology and other related topics and to develop and provide channels and facilities for continuing education in the field.The ISMRM was founded in 1994 through the merger of the Society of Magnetic Resonance in Medicine and the Society of Magnetic Resonance Imaging. SNMMI, ISMRM, and EANM members are physicians, technologists, and scientists specializing in the research and practice of nuclear medicine and/or magnetic resonance imaging. The SNMMI, ISMRM, and EANM will periodically define new guidelines for nuclear medicine practice to help advance the science of nuclear medicine and/or magnetic resonance imaging and to improve the quality of service to patients throughout the world. Existing practice guidelines will be reviewed for revision or renewal, as appropriate, on their fifth anniversary or sooner, if indicated. Each practice guideline, representing a policy statement by the SNMMI/EANM/ISMRM, has undergone a thorough consensus process in which it has been subjected to extensive review. The SNMMI, ISMRM, and EANM recognize that the safe and effective use of diagnostic nuclear medicine imaging and magnetic resonance imaging requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guideline by those entities not providing these services is not authorized. These guidelines are an educational tool designed to assist practitioners in providing appropriate care for patients. They are not inflexible rules or requirements of practice and are not intended, nor should they be used, to establish a legal standard of care. For these reasons and those set forth below, the SNMMI, the ISMRM, and the EANM caution against the use of these guidelines in litigation in which the clinical decisions of a practitioner are called into question. The ultimate judgment regarding the propriety of any specific procedure or course of action must be made by the physician or medical physicist in light of all the circumstances presented. Thus, there is no implication that an approach differing from the guidelines, standing alone, is below the standard of care. To the contrary, a conscientious practitioner may responsibly adopt a course of action different from that set forth in the guidelines when, in the reasonable judgment of the practitioner, such course of action is indicated by the condition of the patient, limitations of available resources, or advances in knowledge or technology subsequent to publication of the guidelines. The practice of medicine includes both the art and the science of the prevention, diagnosis, alleviation, and treatment of disease. The variety and complexity of human conditions make it impossible to always reach the most appropriate diagnosis or to predict with certainty a particular response to treatment. Therefore, it should be recognized that adherence to these guidelines will not ensure an accurate diagnosis or a successful outcome. All that should be expected is that the practitioner will follow a reasonable course of action based on current knowledge, available resources, and the needs of the patient to deliver effective and safe medical care. The sole purpose of these guidelines is to assist practitioners in achieving this objective.

68Ga-PSMA-11 PET/CT versus 68Ga-PSMA-11 PET/MRI for the detection of biochemically recurrent prostate cancer: a systematic review and meta-analysis

Purpose

Our aim was to conduct a meta-analysis and systematic review in order to compare the diagnostic efficacy of 68Ga-PSMA-11 PET/CT and 68Ga-PSMA-11 PET/MRI in patients with biochemically recurrent after radical prostatectomy and biochemically recurrent prostate cancers (BCR) after hybrid RT and RP.

Methods

Up until February 2023, we searched PubMed, Embase, and Web of Science for pertinent papers. Studies examining the utility of 68Ga-PSMA-11 PET/CT or PET/MRI as a screening tool for biochemically recurrent prostate cancer were included. To measure heterogeneity, we employed the I2 statistic. In cases of substantial heterogeneity (I2 > 50%), we used the random effect model to produce a forest plot. In other cases, we utilized the fixed model. Furthermore, we assessed the quality of the studies included using the Quality Assessment of Diagnostic Performance Studies (QUADAS-2) method.

Results

In total, 37 studies involving 8409 patients were examined. For 68Ga-PSMA-11 PET/CT and 68Ga-PSMA-11 PET/MRI, the combined total detection rate was 0.70 (95% CI: 0.65-0.75) and 0.71 (95% CI:0.67-0.75), respectively. 68Ga-PSMA-11 PET/CT and 68Ga-PSMA-11 PET/MRI did not substantially differ in terms of the overall detection rate for BCR (P = 0.58). The detection rate was unaffected by the PSA values (all P > 0.05).

Conclusion

The diagnostic efficacy of 68Ga-PSMA-11 PET/CT appears to be equivalent to that of 68Ga-PSMA-11 PET/MRI in detecting biochemically recurrent prostate cancer. Nonetheless, it should be noted that not all studies have used pathological biopsies as the gold standard. Therefore, additional larger prospective studies are needed to address this issue.

Systematic review registration

identifier CRD42023410039.

The modern therapeutic & imaging landscape of metastatic prostate cancer: a primer for radiologists

Prostate cancer represents one of the leading causes of cancer-related mortality in the United States and the most common cancer among men. Treatment paradigms for the management of advanced stages of prostate cancer have continued to evolve in recent years. These advancements in the therapeutic landscape of metastatic prostate cancer and diagnostic imaging modalities have fundamentally changed the treatment of patients with prostate cancer. In this review article we provide a primer for radiologists highlighting the most recent developments in treatment options and imaging techniques utilized in the modern oncologic management of metastatic prostate cancer. We will examine current therapy options and associated toxicities with an emphasis on relevant imaging findings commonly encountered by radiologists. We also summarize the role of modalities including CT, MRI, PET, bone scintigraphy, and PET in the diagnosis and follow-up of patients with metastatic prostate cancer.

Comparison of MRI, PET, and 18F-choline PET/MRI in patients with oligometastatic recurrent prostate cancer

Objectives

The aims of the study were (i) to examine the PCa detection rate of 18F-choline (FCH) PET/MRI and (ii) to assess the impact of PET/MRI findings in patients with PCa who develop OMD using PSA response as a biomarker.

Methods

We retrospectively analyzed a cohort of 103 patients undergoing FCH PET/MRI for biochemical recurrence of PCa. The inclusion criteria were (1) previous radical prostatectomy (RP) with or without adjuvant radiotherapy (RT); (2) PSA levels available at the time of PET; (3) OMD, defined as a maximum of 5 lesions on PET/MRI; and (4) follow-up data available for at least 6 months after PET. All images were reviewed by two nuclear medicine physicians and interpreted with the support of two radiologists.

Results

Seventy patients were eligible for the study: 52 patients had a positive FCH PET/MRI and 18 had a negative scan. The overall PCa detection rates for MRI, PET, and PET/MRI were 65.7%, 37.1%, and 74.3%, respectively. Thirty-five patients were treated with radiotherapy (RT), 16 received hormonal therapy (HT), 3 had a combined therapy (RT + HT), and 16 (23%) underwent PSA surveillance. At follow-up, PSA levels decreased in 51 patients (73%), most of whom had been treated with RT or RT + HT. Therapeutic management was guided by PET/MRI in 74% of patients, which performed better than MRI alone (68% of patients).

Conclusion

FCH PET/MRI has a higher detection rate than MRI or PET alone for PCa patients with OMD and PSA levels > 0.5 ng/mL, prompting a better choice of treatment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00261-021-03131-7.

PET/MRI in prostate cancer: a systematic review and meta-analysis

Aim

In recent years, the clinical availability of scanners for integrated positron emission tomography (PET) and magnetic resonance imaging (MRI) has enabled the practical potential of multimodal, combined metabolic-receptor, anatomical, and functional imaging to be explored. The present systematic review and meta-analysis summarize the diagnostic information provided by PET/MRI in patients with prostate cancer (PCa).

Materials and methods

A literature search was conducted in three different databases. The terms used were “choline” or “prostate-specific membrane antigen - PSMA” AND “prostate cancer” or “prostate” AND “PET/MRI” or “PET MRI” or “PET-MRI” or “positron emission tomography/magnetic resonance imaging.” All relevant records identified were combined, and the full texts were retrieved. Reports were excluded if (1) they did not consider hybrid PET/MRI; or (2) the sample size was < 10 patients; or (3) the raw data were not enough to enable the completion of a 2 × 2 contingency table.

Results

Fifty articles were eligible for systematic review, and 23 for meta-analysis. The pooled data concerned 2104 patients. Initial disease staging was the main indication for PET/MRI in 24 studies. Radiolabeled PSMA was the tracer most frequently used. In primary tumors, the pooled sensitivity for the patient-based analysis was 94.9%. At restaging, the pooled detection rate was 80.9% and was higher for radiolabeled PSMA than for choline (81.8% and 77.3%, respectively).

Conclusions

PET/MRI proved highly sensitive in detecting primary PCa, with a high detection rate for recurrent disease, particularly when radiolabeled PSMA was used.

Electronic supplementary material

The online version of this article (10.1007/s00259-020-05025-0) contains supplementary material, which is available to authorized users.

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

Background Prostate cancer recurrence is found in up to 40% of men with prior definitive (total prostatectomy or whole-prostate radiation) treatment. Prostate-specific membrane antigen PET agents such as 2-(3-{1-carboxy-5-[(6-[18F]fluoro-pyridine 3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (18F-DCFPyL) may improve detection of recurrence compared with multiparametric MRI; however, histopathologic validation is lacking. Purpose To determine the sensitivity, specificity, and positive predictive value (PPV) of 18F-DCFPyL PET/CT based on histologic analysis and to compare with pelvic multiparametric MRI in men with biochemically recurrent prostate cancer. Materials and Methods Men were prospectively recruited after prostatectomy and/or radiation therapy with rising prostate-specific antigen level (median, 2.27 ng/mL; range, 0.2-27.45 ng/mL) and a negative result at conventional imaging (bone scan and/or CT). Participants underwent 18F-DCFPyL PET/CT imaging and 3.0-T pelvic multiparametric MRI. Statistical analysis included Wald and modified χ2 tests. Results A total of 323 lesions were visualized in 77 men by using 18F-DCFPyL or multiparametric MRI, with imaging detection concordance of 25% (82 of 323) when including all lesions in the MRI field of view and 53% (52 of 99) when only assessing prostate bed lesions. 18F-DCFPyL depicted more pelvic lymph nodes than did MRI (128 vs 23 nodes). Histologic validation was obtained in 80 locations with sensitivity, specificity, and PPV of 69% (25 of 36; 95% confidence interval [CI]: 51%, 88%), 91% (40 of 44; 95% CI: 74%, 98%), and 86% (25 of 29; 95% CI: 73%, 97%) for 18F-DCFPyL and 69% (24 of 35; 95% CI: 50%, 86%), 74% (31 of 42; 95% CI: 42%, 89%), and 69% (24 of 35; 95% CI: 50%, 88%) for multiparametric MRI (P = .95, P = .14, and P = .07, respectively). In the prostate bed, sensitivity, specificity, and PPV were 57% (13 of 23; 95% CI: 32%, 81%), 86% (18 of 21; 95% CI: 73%, 100%), and 81% (13 of 16; 95% CI: 59%, 100%) for 18F-DCFPyL and 83% (19 of 23; 95% CI: 59%, 100%), 52% (11 of 21; 95% CI: 29%, 74%), and 66% (19 of 29; 95% CI: 44%, 86%) for multiparametric MRI (P = .19, P = .02, and P = .17, respectively). The addition of 18F-DCFPyL to multiparametric MRI improved PPV by 38% overall (P = .02) and by 30% (P = .09) in the prostate bed. Conclusion Findings with 2-(3-{1-carboxy-5-[(6-[18F]fluoro-pyridine 3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (18F-DCFPyL) were histologically validated and demonstrated high specificity and positive predictive value. In the pelvis, 18F-DCFPyL depicted more lymph nodes and improved positive predictive value and specificity when added to multiparametric MRI. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Zukotynski and Rowe in this issue.

68Ga-PSMA-11 PET/MRI: determining ideal acquisition times to reduce noise and increase image quality

Background

In this study, we investigate the impact of increased PET acquisition time per bed position on lesion detectability, standard uptake value, and image noise in ⁶⁸Ga-PSMA-11 PET/MRI scans.

Methods

Scans of twenty patients were analyzed in this study. Patients were injected with ⁶⁸Ga-PSMA-11 (mean, 5.50 ± 1.49 mCi) and imaged on a 3.0 T time-of-flight PET/MRI. PET images were retrospectively reconstructed using 0.5, 1, 2, 4, 7, and 10 min of PET data. Lesion detectability was evaluated on a 5-point Likert Scale for each lesion in each reconstruction. Quantitative analysis was performed measuring image noise and lesion uptake.

Results

A total of 55 lesions were identified, and lesion detectability increased from 2.07 ± 1.14 for 0.5 min to 4.93 ± 0.26 for 10 min (p < 0.001), with no significant difference detected between 7 and 10 min of scan time. Average SUV_max decreased from 9.89 ± 6.62 for 0.5 min to 8.64 ± 6.81 for 10 min. Noise decreased from 0.72 ± 0.22 for 0.5 min to 0.31 ± 0.12 for 10 min (p < 0.001) and were nearly equivalent between 7 and 10 min. Pairwise interaction terms between size, SUV_max, and scan time were all found to be significant, although the interaction term between SUV_max and scan time was found to be the most significant.

Conclusions

Increased acquisition duration improves image quality by increasing detectability and reducing noise. In patients with biochemical recurrence, increased acquisition time up to 7 min improves lesion detection.

Fluorodeoxyglucose positron-emission tomography-magnetic resonance hybrid imaging: An emerging tool for staging of cancer of the uterine cervix

Positron-emission tomography-magnetic resonance imaging (PET-MRI) is an emerging hybrid imaging modality that utilizes the superior soft tissue resolution of MR with the metabolic data from PET. In this study, we sought to assess the clinical value of fluorodeoxyglucose (FDG) PET-MRI with dedicated pelvic PET-MR in the initial staging of cervical cancer. In this institutional-approved study, we identified 23 adult females who underwent FDG PET-MRI on hybrid camera for staging of primary uterine cervical cancer that included a dedicated PET-MR of the pelvis. A nuclear medicine physician and a radiologist reviewed the PET, MRI, and fusion-body and pelvis images alone and then with consensus read characterizing PET and MR abnormal findings. There were 23 patients who underwent FDG PET-MRI for initial staging of cervical cancer with an average age of 52.2 ± 14.0 years. A total of 23 suspected lymph nodes in eight different patients were detected within the pelvis with increased metabolic activity on PET. Both the dedicated pelvis and whole-body PET imaging detected the same corresponding pelvic lymph nodes, although the pelvic PET imaging had better lymph node uptake delineation due to longer acquisition time. Using a 10-mm short-axis criterion, MRI identified only 43.5% of the FDG avid lymph nodes. The average SUVmax on the pelvis PET sequences was higher with SUV 8.9 ± 5.2 compared to the whole-body PET with SUV 7.8 ± 5.4 but was not statistically significant (P > 0.05). Primary cervical cancer was identified in 18 patients on both PET imaging and MRI with dedicated MR pelvis providing better characterization. Based on our results of the patients with cervical cancer evaluated for initial staging, combining dedicated pelvic PET-MRI with whole-body PET/MR provides the most complete status of malignant disease in reference to delineation of primary tumor, involvement of surrounding tissues, and regional lymph nodes.

68 Ga-PSMA-PET/CT helps to select patients for salvage radical prostatectomy with local recurrence after primary radiotherapy for prostate cancer

OBJECTIVE

To investigate the diagnostic performance of gallium-68 prostate-specific membrane antigen positron emission tomography/computed tomography (⁶⁸ Ga-PSMA PET/CT) in patients with recurrent prostate cancer with regard to the presence of lymph node metastases (LNM) and local recurrences after primary radiotherapy.

PATIENTS AND METHODS

We retrospectively reviewed 142 patients following salvage radical prostatectomy (sRP), 50 of which had a ⁶⁸ Ga-PSMA PET/CT performed as a preoperative staging module. Predictive clinical parameters were analysed in a multivariate Cox regression analysis. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) and the accuracy of ⁶⁸ Ga-PSMA PET/CT were analysed with regard to LNM and local recurrence.

RESULTS

In all, 613 lymph nodes were resected in 40 patients and 23 lymph nodes had metastatic deposits in 14 patients. In all patients local recurrence could have been found with ⁶⁸ Ga-PSMA PET/CT. Sensitivity, specificity, PPV and NPV and accuracy on a per lymph node basis were 34.78% (16.38-57.2%), 100% (99.38-100%), 100%, 97.52% (96.69-98.15%) and 97.55% (96.00-98.62%). For detecting local recurrence, the sensitivity and PPV were both 100% with an accuracy of 100% (92.89-100%).

CONCLUSION

⁶⁸ Ga-PSMA PET/CT should be the standard imaging in biochemical recurrent prostate cancer. With this imaging module one detects first local recurrence and can detect locoregional and distant metastases more precisely than standard CT and bone scan.

68Ga-PSMA PET/MRI for the diagnosis of primary and biochemically recurrent prostate cancer: A meta-analysis

PURPOSE

Our meta-analysis aimed to evaluate the diagnostic performance of ⁶⁸Ga-labelled prostate-specific membrane antigen ligand positron emission tomography/magnetic resonance imaging (⁶⁸Ga-PSMA PET/MRI) in patients with primary and biochemically recurrent prostate cancer (PCa).

METHODS

We searched for relevant articles in PubMed, EMBASE, the Cochrane Library and Web of Science until September 12, 2019. Studies regarding the diagnostic performance of⁶⁸Ga-PSMA PET/MRI in detecting primary PCa and biochemical recurrence (BCR) after definitive treatment were included. The quality of each study was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. The pooled sensitivity and specificity of PET/MRI in identifying primary PCa and the pooled detection rate of PET/MRI for BCR were calculated using a random-effects model.

RESULTS

A total of 13 studies with 707 patients were included in the analysis, and the pooled sensitivity and specificity of PET/MRI in detecting primary PCa were 0.83 (95 % CI, 0.73-0.90) and 0.81 (95 % CI, 0.61-0.93), respectively. In the pooled analysis of BCR, the pooled detection rate was 76 % (95 % CI, 72 %-79 %). For four levels of PSA (0-0.2 ng/mL, 0.2-1 ng/mL, 1-2 ng/mL and more than 2 ng/mL), the pooled detection rates were 38 %, 67 %, 74 %, and 95 %, respectively. There was no distinct publication bias, but there was significant study heterogeneity.

CONCLUSIONS

⁶⁸Ga-PSMA PET/MRI is likely an effective imaging method in the diagnosis of primary PCa. In addition, the diagnostic accuracy of ⁶⁸Ga-PSMA PET/MRI in patients with BCR was also high, positively correlating with PSA levels.

Factors Predicting Metastatic Disease in 68Ga-PSMA-11 PET-Positive Osseous Lesions in Prostate Cancer

Bone is the most common site of distant metastatic spread in prostate adenocarcinoma. Prostate-specific membrane antigen (PSMA) uptake has been described in both benign and malignant bone lesions, which can lead to false-positive findings on ⁶⁸Ga-PSMA-11 PET. The purpose of this study was to evaluate the diagnostic accuracy of ⁶⁸Ga-PSMA-11 PET for osseous prostate cancer metastases and improve bone uptake interpretation using semiquantitative metrics. Methods: Fifty-six prostate cancer patients (18 before prostatectomy and 38 with biochemical recurrence) who underwent ⁶⁸Ga-PSMA-11 PET/MRI or PET/CT examinations with osseous PSMA-ligand uptake were included in the study. Medical records were reviewed retrospectively by board-certified nuclear radiologists to determine true or false positivity based on a composite endpoint. For each avid osseous lesion, we measured biologic volume; size; PSMA Reporting and Data System (RADS) rating; SUV_max; and ratio of lesion SUV_max to liver, blood pool, and background bone SUV_max Differences between benign and malignant lesions were evaluated for statistical significance, and cutoffs for these parameters were determined to maximize diagnostic accuracy. Results: Among 56 participants, 13 (22.8%) had false-positive osseous ⁶⁸Ga-PSMA-11 findings and 43 (76.8%) had true-positive osseous ⁶⁸Ga-PSMA-11 findings. Twenty-two patients (39%) had 1 osseous lesion, 18 (32%) had 2-4 lesions, and 16 (29%) had 5 or more lesions. Cutoffs resulting in statistically significant (P < 0.005) differences between benign and malignant lesions were a PSMA RADS rating of at least 4, an SUV_max of at least 4.1, and SUV_max ratios of at least 2.11 for lesion to blood pool, at least 0.55 for lesion to liver, and at least 4.4 for lesion to bone. These measurements corresponded to a lesion-based ⁶⁸Ga-PSMA-11 PET lesion detection rate of 80%, 93%, 89%, 21%, and 89%, respectively, for malignancy, and a specificity of 73%, 73%, 73%, 93%, and 60%, respectively. Conclusion: PSMA RADS rating, SUV_max, and SUV_max ratio for lesion to blood pool can help differentiate benign from malignant lesions on ⁶⁸Ga-PSMA-11 PET. An SUV_max ratio of more than 2.2 for lesion to blood pool is a reasonable parameter to support image interpretation and presented a superior lesion detection rate and specificity when compared with visual interpretation by PSMA RADS. These parameters hold clinical value by improving diagnostic accuracy for metastatic prostate cancer on ⁶⁸Ga-PSMA-11 PET/MRI and PET/CT.

Assessment of 68Ga-PSMA-11 PET Accuracy in Localizing Recurrent Prostate Cancer: A Prospective Single-Arm Clinical Trial

Importance

In retrospective studies, 68Ga-PSMA-11 positron emission tomographic (PET) imaging improves detection of biochemically recurrent prostate cancer compared with conventional imaging.

Objective

To assess 68Ga-PSMA-11 PET accuracy in a prospective multicenter trial.

Design, Setting, and Participants

In this single-arm prospective trial conducted at University of California, San Francisco and University of California, Los Angeles, 635 patients with biochemically recurrent prostate cancer after prostatectomy (n = 262, 41%), radiation therapy (n = 169, 27%), or both (n = 204, 32%) underwent 68Ga-PSMA-11 PET. Presence of prostate cancer was recorded by 3 blinded readers on a per-patient and per-region base. Lesions were validated by histopathologic analysis and a composite reference standard.

Main Outcomes and Measures

Endpoints were positive predictive value (PPV), detection rate, interreader reproducibility, and safety.

Results

A total of 635 men were enrolled with a median age of 69 years (range, 44-95 years). On a per-patient basis, PPV was 0.84 (95% CI, 0.75-0.90) by histopathologic validation (primary endpoint, n = 87) and 0.92 (95% CI, 0.88-0.95) by the composite reference standard (n = 217). 68Ga-PSMA-11 PET localized recurrent prostate cancer in 475 of 635 (75%) patients; detection rates significantly increased with prostate-specific antigen (PSA): 38% for <0.5 ng/mL (n = 136), 57% for 0.5 to <1.0 ng/mL (n = 79), 84% for 1.0 to <2.0 ng/mL (n = 89), 86% for 2.0 to <5.0 ng/mL (n = 158), and 97% for ≥5.0 ng/mL (n = 173, P < .001). Interreader reproducibility was substantial (Fleiss κ, 0.65-0.78). There were no serious adverse events associated with 68Ga-PSMA-11 administration. PET-directed focal therapy alone led to a PSA drop of 50% or more in 31 of 39 (80%) patients.

Conclusions and Relevance

Using blinded reads and independent lesion validation, we establish high PPV for 68Ga-PSMA-11 PET, detection rate and interreader agreement for localization of recurrent prostate cancer.

Trial Registration

ClinicalTrials.gov identifiers: NCT02940262 and NCT03353740.

Imaging for Metastasis in Prostate Cancer: A Review of the Literature

Background: Initial staging and assessment of treatment activity in metastatic prostate cancer (PCa) patients is controversial. Indications for the various available imaging modalities are not well-established due to rapid advancements in imaging and treatment.

Methods: We conducted a critical literature review of the main imaging abnormalities that suggest a diagnosis of metastasis in localized and locally advanced PCa or in cases of biological relapse. We also assessed the role of the various imaging modalities available in routine clinical practice for the detection of metastases and response to treatment in metastatic PCa patients.

Results: In published clinical trials, the most commonly used imaging modalities for the detection and evaluation of therapeutic response are bone scan, abdominopelvic computed tomography (CT), and pelvic and bone magnetic resonance imaging (MRI). For the detection and follow-up of metastases during treatment, modern imaging techniques i.e., choline-positron emission tomography (PET), fluciclovine-PET, or Prostate-specific membrane antigen (PSMA)-PET provide better sensitivity and specificity. This is particularly the case of fluciclovine-PET and PSMA-PET in cases of biochemical recurrence with low values of prostate specific antigen.

Conclusions: In routine clinical practice, conventional imaging still have a role, and communication between imagers and clinicians should be encouraged. Present and future clinical trials should use modern imaging methods to clarify their usage.

Summary of the First ISMRM-SNMMI Workshop on PET/MRI: Applications and Limitations

Since the introduction of simultaneous PET/MRI in 2011, there have been significant advancements. In this review, we highlight several technical advancements that have been made primarily in attenuation and motion correction and discuss the status of multiple clinical applications using PET/MRI. This review is based on the experience at the first PET/MRI conference cosponsored by the International Society for Magnetic Resonance in Medicine and the Society of Nuclear Medicine and Molecular Imaging.

Prostate-Specific Membrane Antigen PET/Magnetic Resonance Imaging for the Planning of Salvage Radiotherapy in Patients with Prostate Cancer with Biochemical Recurrence After Radical Prostatectomy

This article presents an overview of the current literature on PET imaging with prostate-specific membrane antigen ligands, especially focusing on the potential role of simultaneous PET/magnetic resonance imaging for the planning of salvage radiotherapy in patients with prostate cancer with biochemical recurrence after radical prostatectomy.

PEG-coated and Gd-loaded fluorescent silica nanoparticles for targeted prostate cancer magnetic resonance imaging and fluorescence imaging

Background: Multimodal imaging probes have become a powerful tool for improving detection sensitivity and accuracy, which are important in disease diagnosis and treatment.

Methods: In this study, novel bifunctional magnetic resonance imaging (MRI)/fluorescence probes were prepared by loading gadodiamide into fluorescent silica nanoparticles (NPs) (Gd@Cy5.5@SiO₂-PEG-Ab NPs) for targeting of prostate cancer (PCa). The physicochemical characteristics, biosafety and PCa cell targeting ability of the Gd@Cy5.5@SiO₂-PEG-Ab NPs were studied in vitro and in vivo.

Results: The Gd@Cy5.5@SiO₂-PEG-Ab NPs had a spherical morphology with a relatively uniform size distribution and demonstrated high efficiency for Gd loading. In vitro and in vivo cell-targeting experiments demonstrated a high potential for the synthesized NPs to target prostate-specific membrane antigen (PSMA) receptor-positive PCa cells, enabling MRI and fluorescence imaging. In vitro cytotoxicity assays and in vivo hematological and pathological assays showed that the prepared NPs exhibited good biological safety.

Conclusion: Our study demonstrates that the synthesized Gd@Cy5.5@SiO₂-PEG-Ab NPs have great potential as MRI/fluorescence contrast agents for specific identification of PSMA receptor-positive PCa cells.

Management of Metastatic Hormone-Sensitive Prostate Cancer (mHSPC): an Evolving Treatment Paradigm

OPINION STATEMENT

Combination systemic therapy is now standard of care for all men with metastatic, hormone-sensitive prostate cancer (mHSPC). Patients with mHSPC should be treated with standard androgen deprivation therapy (ADT) and abiraterone acetate with prednisone or docetaxel (chemohormoanl therapy) unless there are contraindications to combination therapy. Based on the Chemohormonal Therapy Versus Androgen Ablation Randomized Trial for Extensive Disease in Prostate Cancer (CHAARTED) study subgroup analysis, chemohormonal therapy may be most beneficial in men with high-volume disease burden, as men with low-volume metastatic disease do not appear to experience a survival benefit with chemohormonal therapy, while abiraterone in combination with ADT appears to be beneficial across both disease volume subgroups. Decisions regarding whether to use chemohormonal therapy or abiraterone and ADT for men with mHSPC should integrate consideration of volume of disease burden, quality of life effects, duration of therapy, and patient preferences for treatment as there is no formally powered prospective head-to-head comparison of these options demonstrating superiority of one approach over the other. Treatment of the primary tumor with radiation should be considered in men with de novo low-volume metastatic disease as radiation is associated with prolonged survival and a tolerable toxicity profile. Men with de novo high-volume metastatic disease do not appear to have improved survival with radiation of the primary tumor. Numerous clinical trials are ongoing to evaluate treatment approaches that may benefit men with mHSPC. Radical prostatectomy in men with mHSPC in combination with optimal systemic therapy is currently being assessed in a clinical trial, but should not be considered outside of a clinical trial. Metastasis-directed therapy with radiotherapy directed at metastatic lesions is still investigational, but can be considered in clinical trials in men with oligometastatic disease. Multiple studies are enrolling worldwide for men with mHSPC, and these should be considered for all interested patients.

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

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

Gallium-68 Prostate-specific Membrane Antigen Positron Emission Tomography in Advanced Prostate Cancer-Updated Diagnostic Utility, Sensitivity, Specificity, and Distribution of Prostate-specific Membrane Antigen-avid Lesions: A Systematic Review and Meta-analysis

CONTEXT

Accurate staging of high-risk localised, advanced, and metastatic prostate cancer is becoming increasingly more important in guiding local and systemic treatment. Gallium-68 prostate-specific membrane antigen (PSMA) positron emission tomography (PET) has increasingly been utilised globally to assess the local and metastatic burden of prostate cancer, typically in biochemically recurrent or advanced disease. Following our previous meta-analysis, a high-volume series has been reported highlighting the utility of ⁶⁸Ga-PSMA PET in this setting.

OBJECTIVE

To perform a systematic review and meta-analysis to update reported predictors of positive ⁶⁸Ga-PSMA PET according to prior therapy and proportion of positivity in various anatomical locations with sensitivity and specificity profiles.

EVIDENCE ACQUISITION

We performed critical reviews of MEDLINE, EMBASE, ScienceDirect, Cochrane Libraries, and Web of Science databases in July 2018 according to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement. Quality assessment was performed using Quality Assessment if Diagnostic Accuracy Studies-2 tool. Meta-analyses of proportions were performed using a random-effect model. Summary sensitivity and specificity values were obtained by fitting bivariate hierarchical regression models.

EVIDENCE SYNTHESIS

A total of 37 articles including 4790 patients were analysed. For patients with biochemical recurrence, positive ⁶⁸Ga-PSMA PET scans increased with higher pre-PET prostate-specific antigen (PSA) levels. For PSA categories 0-0.19, 0.2-0.49, 0.5-0.99, 1-1.99, and ≥2ng/ml, the percentages of positive scans were 33%, 45%, 59%, 75%, and 95%, respectively. No significant differences in positivity were noted between Gleason sums ≤7 and ≥8. Significant differences in positivity after biochemical recurrence in the prostate bed were noted between radical prostatectomy (22%) and radiotherapy (52%) patients. On per-node analysis, high sensitivity (75%) and specificity (99%) were observed.

CONCLUSIONS

Ga-68-PSMA PET improves detection of metastases with biochemical recurrence, particularly at low pre-PET PSA levels of >0.2ng/ml (33%) and 0.2-0.5ng/ml (45%). Ga-68-PSMA-PET produces favourable sensitivity and specificity profiles on meta-analysis of pooled data. This analysis highlights different anatomic patterns of metastatic spread according to PSMA PET in the primary and biochemically recurrent settings.

PATIENT SUMMARY

Gallium-68 prostate-specific membrane antigen positron emission tomography is now an established imaging technique that has been developed in response to inadequacies in standard of care imaging modalities to improve the detection of metastatic disease in prostate cancer, particularly in the setting of disease recurrence. To date, this imaging modality in the setting of primary staging is controversial, given the paucity of data. In light of the growing body of evidence, we summarised the data to date to provide clinicians with an overview of this imaging modality.

Metaanalysis of 68Ga-PSMA-11 PET Accuracy for the Detection of Prostate Cancer Validated by Histopathology

⁶⁸Ga-PSMA-11 PET is used to stage patients with prostate cancer. We performed an updated metaanalysis that separates imaging at the time of diagnosis and at the time of biochemical recurrence and focuses on pathology correlation in both populations. Methods: We searched the MEDLINE and EMBASE databases using the PRISMA statement. Quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool 2. In total, 1,811 studies were screened, 58 were analyzed, 41 were included for qualitative synthesis, and 29 were included for quantitative analysis. A random-effect model and a hierarchical summary receiver-operating-characteristic model were used to summarize the sensitivity, specificity, positive predictive value (PPV), negative predictive value, and accuracy for pelvic lymph nodes in initial staging compared with pathology at prostatectomy and the PPV for lesions with pathologic correlation in those with biochemical recurrence. We also summarized the detection rate of ⁶⁸Ga-PSMA-11 in those with biochemical recurrence stratified by prostate-specific antigen (PSA) at the time of imaging. Results: The metaanalysis of ⁶⁸Ga-PSMA-11 at initial staging demonstrated a sensitivity and specificity of 0.74 (95% confidence interval [95% CI], 0.51-0.89) and 0.96 (95% CI, 0.85-0.99), respectively, using nodal pathology at prostatectomy as a gold standard. At biochemical recurrence, the PPV was 0.99 (95% CI, 0.96-1.00). The detection rate was 0.63 (95% CI, 0.55-0.70), with a PSA of less than 2.0 and 0.94 (95% CI, 0.91-0.96) with a PSA of more than 2.0. Conclusion: ⁶⁸Ga-PSMA-11 performed well for the localization of metastatic prostate cancer at initial staging and at the time of biochemical recurrence.

Does Extended PET Acquisition in PET/MRI Rectal Cancer Staging Improve Results?

OBJECTIVE

The purpose of this study was to determine if extended PET acquisition times in the pelvis during PET/MRI increase detection rates of potentially metastatic lymph nodes in patients with rectal cancer.

MATERIALS AND METHODS

Our study was approved by the institutional review board of the University of California, San Francisco. Twenty-two patients with biopsy-proven rectal cancer underwent imaging via simultaneous 3-T time-of-flight PET/MRI, with seven undergoing two separate PET/MRI examinations, for a total of 29 studies. Each examination included both a whole-body PET/MRI and a dedicated pelvic PET/MRI with both 3- and 15-minute PET acquisitions for the pelvis. Three radiologists interpreted each examination with PET only, MRI only, then combined PET and MRI examinations, using all available images. Additionally, the 3- and 15-minute PET acquisitions of the pelvis were reviewed separately by a single radiologist.

RESULTS

A total of 94 lymph nodes were identified as abnormal on PET, all with MRI anatomic correlates. Of these, 37 (39.4%) were seen only on the dedicated 15-minute acquisition. Fifty-seven (60.6%) nodes measured 5 mm or less, including 29 (30.9%) seen only on the 15-minute acquisition. Thirty-one (33.0%) nodes measured 5.1-10 mm, including eight (25.8%) seen only on the 15-minute acquisition. Of the 17 subjects imaged for initial staging, 11 (64.7%) were upstaged as a result of the increased PET acquisition time (10 from N1 to N2 and one from N0 to N1).

CONCLUSION

Longer PET acquisition times during PET/MRI for rectal cancer increases the number of FDG-avid lymph nodes detected without increasing scan time.

Positron emission tomography in prostate cancer: An update on state of the art

Prostate cancer (PCa), one of the most common cancers in males, is a topic of active interest in imaging research. Positron emission tomography/computed tomography (PET/CT) and PET/magnetic resonance imaging (PET/MRI) have enabled the combination of morphologic and functional imaging with the promise of providing better information in guiding therapy. ¹⁸F-fluorodeoxyglucose, the workhorse radiopharmaceutical in PET imaging, has not found preference in PCa since these tumors show poor glucose uptake and can be obscured by the normal urinary excretion of the radiotracer. Hence, the last two decades have seen the development of multiple newer radiotracers and better optimization of the technical aspects of PET imaging. The combination of functional imaging and MRI holds great promise. We searched PubMed, Scopus, and Google Scholar for peer-reviewed literature concerning the advances and newer developments in the imaging of PCa between the years 2005 and 2017. This review aims at summarizing current evidence on the role of PET imaging in PCa and its impact on the diagnosis, staging, prognostication, response assessment, and restaging of this malignancy.

Imaging Prostate Cancer With Prostate-Specific Membrane Antigen PET/CT and PET/MRI: Current and Future Applications

OBJECTIVE

The purpose of this article is to describe the large number of radiotracers being evaluated for prostate-specific membrane antigen (PSMA) PET, which is becoming a central tool in the staging of prostate cancer.

CONCLUSION

PSMA PET is a highly promising modality for the staging of prostate cancer because of its higher detection rate compared with that of conventional imaging. Both PET/CT and PET/MRI offer benefits with PSMA radiotracers, and PSMA PET findings frequently lead to changes in management. It is imperative that subsequent treatment changes be evaluated to show improved outcomes. PSMA PET also has potential applications, including patient selection for PSMA-based radioligand therapy and evaluation of treatment response.

Clinical Evaluation of 68Ga-PSMA-II and 68Ga-RM2 PET Images Reconstructed With an Improved Scatter Correction Algorithm

OBJECTIVE

Gallium-68-labeled radiopharmaceuticals pose a challenge for scatter estimation because their targeted nature can produce high contrast in these regions of the kidneys and bladder. Even small errors in the scatter estimate can result in washout artifacts. Administration of diuretics can reduce these artifacts, but they may result in adverse events. Here, we investigated the ability of algorithmic modifications to mitigate washout artifacts and eliminate the need for diuretics or other interventions.

MATERIALS AND METHODS

The model-based scatter algorithm was modified to account for PET/MRI scanner geometry and challenges of non-FDG tracers. Fifty-three clinical ⁶⁸Ga-RM2 and ⁶⁸Ga-PSMA-11 whole-body images were reconstructed using the baseline scatter algorithm. For comparison, reconstruction was also processed with modified sampling in the single-scatter estimation and with an offset in the scatter tail-scaling process. None of the patients received furosemide to attempt to decrease the accumulation of radiopharmaceuticals in the bladder. The images were scored independently by three blinded reviewers using the 5-point Likert scale.

RESULTS

The scatter algorithm improvements significantly decreased or completely eliminated the washout artifacts. When comparing the baseline and most improved algorithm, the image quality increased and image artifacts were reduced for both ⁶⁸Ga-RM2 and for ⁶⁸Ga-PSMA-11 in the kidneys and bladder regions.

CONCLUSION

Image reconstruction with the improved scatter correction algorithm mitigated washout artifacts and recovered diagnostic image quality in ⁶⁸Ga PET, indicating that the use of diuretics may be avoided.