68Ga-FAPI-04 positron emission tomography/CT and laparoscopy for the diagnosis of occult peritoneal metastasis in newly diagnosed locally advanced gastric cancer: study protocol of a single-centre prospective cohort study.

INTRODUCTION: Accurate baseline clinical staging is critical to inform treatment decision-making for patients with gastric cancers. Peritoneal metastasis (PM) is the most common form of metastasis in gastric cancer and mainly diagnosed by diagnostic laparoscopy and peritoneal lavage evaluation. However, diagnostic laparoscopy is invasive and less cost-effective. It is urgent to develop a safe, fast and non-invasive functional imaging method to verify the peritoneal metastasis of gastric cancer. The aim of our study was to evaluate the proportion of patients in whom 68Ga-FAPI-04 positron emission tomography/CT (PET/CT) led to a change in treatment strategy and to assess the diagnostic accuracy of 68Ga-FAPI-04 PET/CT for the detection of occult peritoneal metastasis compared with laparoscopic exploration. METHODS AND ANALYSIS: In this single-centre, prospective diagnostic test accuracy study, a total of 48 patients with locally advanced gastric or gastro-oesophageal junction adenocarcinoma (cT4a-b, N0-3, M0, based on CT images) who are considering radical tumour surgery will be recruited. All participants will undergo 68Ga-FAPI-04 PET/CT before the initiation of laparoscopic exploration. The primary outcome is the proportion of patients with occult peritoneal metastatic lesions detected by 68Ga-FAPI-04 PET/CT, leading to a change in therapy strategy. The secondary outcomes include the diagnostic performance of 68Ga-FAPI-04 PET/CT for occult peritoneal metastasis, including sensitivity, specificity, accuracy, positive predictive value and negative predictive value. ETHICS AND DISSEMINATION: The study protocol was approved by the Ethics Committee of West China Hospital, Sichuan University (2022-1484). Study results will be presented at public and scientific conferences and in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ChiCTR2300067591.

Struma Ovarii With Extensive Peritoneal Implants Metastasis Revealed by 99m TcO 4 SPECT/CT.

ABSTRACT: Struma ovarii is a rare form of ovarian teratoma composed entirely or mainly of mature thyroid tissue. A 55-year-old woman with persistent hypogastric pain for 4 months was admitted to our hospital. She had undergone resection of struma ovarii 4 years ago. Contrast-enhanced CT shows multiple significantly enhanced nodules scattered in the abdominopelvic cavity. Pathological examination of the nodule in the left pararenal region demonstrated thyroid-like follicular epithelium. Herein, we present the 99m TcO 4 whole-body scintigraphy SPECT/CT findings of a case of struma ovarii with extensive peritoneal implants metastasis. Then, she was treated with total thyroidectomy and 131 I therapy.

Imaging Evaluation of Peritoneal Metastasis: Current and Promising Techniques.

Early diagnosis, accurate assessment, and localization of peritoneal metastasis (PM) are essential for the selection of appropriate treatments and surgical guidance. However, available imaging modalities (computed tomography [CT], conventional magnetic resonance imaging [MRI], and 18fluorodeoxyglucose positron emission tomography [PET]/CT) have limitations. The advent of new imaging techniques and novel molecular imaging agents have revealed molecular processes in the tumor microenvironment as an application for the early diagnosis and assessment of PM as well as real-time guided surgical resection, which has changed clinical management. In contrast to clinical imaging, which is purely qualitative and subjective for interpreting macroscopic structures, radiomics and artificial intelligence (AI) capitalize on high-dimensional numerical data from images that may reflect tumor pathophysiology. A predictive model can be used to predict the occurrence, recurrence, and prognosis of PM, thereby avoiding unnecessary exploratory surgeries. This review summarizes the role and status of different imaging techniques, especially new imaging strategies such as spectral photon-counting CT, fibroblast activation protein inhibitor (FAPI) PET/CT, near-infrared fluorescence imaging, and PET/MRI, for early diagnosis, assessment of surgical indications, and recurrence monitoring in patients with PM. The clinical applications, limitations, and solutions for fluorescence imaging, radiomics, and AI are also discussed.

Intense FDG Uptake in Leiomyomatosis Peritonealis Disseminata With Fumarate Hydratase Deficiency.

ABSTRACT: A 35-year-old woman with a history of laparoscopic myomectomy presented with repeated abdominal pain. Contrast-enhanced abdominal and pelvic CT showed multiple enhancing solid or mixed cystic and solid peritoneal masses, and an enhancing uterine mass. All these masses showed intense FDG uptake on FDG PET/CT. The intraperitoneal and uterine masses were surgically removed. The histological and immunohistochemical findings of the peritoneal lesions were consistent with leiomyomatosis peritonealis disseminata with fumarate hydratase deficiency, and the uterine mass was adenomyosis. This case indicates fumarate hydratase-deficient extrauterine leiomyoma can show intense FDG uptake mimicking malignancy.

Malignant Peritoneal Mesothelioma Complicating Familial Mediterranean Fever on 18 F-FDG PET/CT.

ABSTRACT: A 77-year-old man with a personal history of familial Mediterranean fever presented with a slowly enlarging tumefaction of the left abdominal wall and persistent inflammatory syndrome despite good adherence to colchicine. 18 F-FDG PET/CT showed a hypermetabolic muscular mass of the abdominal wall along with other hypermetabolic lesions including a peritoneal mass and several subcutaneous soft tissue nodules. CT-guided needle biopsy led to the diagnosis of a muscular localization of a malignant peritoneal mesothelioma, which is an extremely rare complication of familial Mediterranean fever. Six courses of chemotherapy with carboplatin and pemetrexed allowed an almost complete response.

CT texture analysis for differentiating between peritoneal carcinomatosis and peritoneal tuberculosis: a cross-sectional study.

PURPOSE: Peritoneal carcinomatosis (PC) and peritoneal tuberculosis (PTB) have similar clinical and radiologic imaging features, which make it very difficult to differentiate between the two entities clinically. Our aim was to determine if the CT textural parameters of omental lesions among patients with PC were different from those with PTB. METHODS: All patients who had undergone omental biopsy at our institution from January 2010 to December 2018 and had a tissue diagnosis of PC or PTB were eligible for inclusion. Patients who did not have a contrast-enhanced CT abdomen within one month of the omental biopsy were excluded. A region of interest (ROI) was manually drawn over omental lesions and radiomic features were extracted using open-source LIFEx software. Statistical analysis was performed to compare mean differences in CT texture parameters between the PC and PTB groups. RESULTS: A total of 66 patients were included in the study of which 38 and 28 had PC and PTB, respectively. Omental lesions in patients with PC had higher mean radiodensity (mean difference: +32.4; p = 0.001), higher mean entropy (mean difference: +0.11; p < 0.001), and lower mean energy (mean difference: -0.024; p = 0.001) compared to those in PTB. Additionally, omental lesions in the PC group had lower gray-level co-occurrence matrix (GLCM) homogeneity (mean difference: -0.073; p < 0.001) and higher GLCM dissimilarity (mean difference: +0.480; p < 0.001) as compared to the PTB group. CONCLUSION: CT texture parameters of omental lesions differed significantly between patients with PTB and those with PC, which may help clinicians in differentiating between the two entities.

Bland-Altman agreement analysis between CT predicted and surgical peritoneal cancer index in pseudomyxoma peritonei of appendiceal origin.

Peritoneal cancer index (PCI) is the surgical variable most commonly used to quantify the extent of peritoneal metastases for pseudomyxoma peritonei (PMP) patients. The present study aimed to investigate the agreement between CT predicted and surgical PCI by the Bland-Altman method for PMP of appendiceal origin. A total of 167 PMP patients of appendiceal origin were included between 2016 and 2021. Bland-Altman analysis was performed for both total PCI and selected PCI (regions 2 + 9-12). After the Bland-Altman plot was drawn, the mean bias and its 95% limit of agreements (LoAs) was quantified. Besides, the correlation coefficients between CT-PCI and surgical PCI were also been calculated. The Bland-Altman plot showed the mean bias ± SD between total CT-PCI and surgical PCI as 0.431 ± 3.005, with the LoAs from - 5.459 to 6.321. There were nine points of difference in total PCI exceeded the 95% LoAs, with the rate of 5.39% (9/167). As for selected CT-PCI, Bland-Altman plot showed the mean bias ± SD between selected CT-PCI and surgical PCI as - 0.287 ± 1.955, with the LoAs from - 4.118 to 3.544. There were ten points of difference in selected PCI exceeded the 95% LoAs, with the rate of 5.99% (10/167). The Spearman's rank correlation coefficient between total CT-PCI and surgical PCI was 0.911, P < 0.001, as for selected CT-PCI and surgical PCI, the coefficient was 0.909, P < 0.001. Although there was a strong correlation for both total and selected CT-PCI with surgical PCI, however, the agreement is still not good in Bland-Altman analysis, which suggested that CT-PCI cannot predict surgical PCI accurately even in professional PMP treatment centers. In brief explanation, CT makes it difficult to distinguish the borderline between tumor tissue and mucus and to detect tumor lesions in the small intestine regions, which caused overestimation or underestimation by CT-PCI. In the future, a multiple linear regression model based on CT-PCI might accurately predict surgical PCI preoperatively.

Development of a Nomogram to Predict Postoperative Peritoneal Metastasis of Colon Cancer.

OBJECTIVE: The aim of this study was to determine the clinicopathological and radiological risk factors for postoperative peritoneal metastasis and develop a prediction model for the early detection of peritoneal metastasis in patients with colon cancer. METHODS: We included 174 patients with colon cancer. The clinicopathological and radiological data were retrospectively analyzed. A Cox proportional hazards regression model was used to identify risk factors for postoperative peritoneal metastasis. Based on these risk factors, a nomogram was developed. RESULTS: At a median follow-up of 63 months, 43 (24.7%) patients developed peritoneal metastasis. Six independent risk factors (hazards ratio [95% confidence interval]) were identified for postoperative peritoneal metastasis: abdominopelvic fluid (2.12 [1.02-4.40]; P = 0.04), longer maximum tumor length (1.02 [1.00-1.03]; P = 0.02), pN1 (2.50 [1.13-5.56]; P = 0.02), pN2 (4.45 [1.77-11.17]; P = 0.02), nonadenocarcinoma (2.75 [1.18-6.38]; P = 0.02), and preoperative carcinoembryonic antigen levels ≥5 ng/mL (3.08 [1.50-6.30]; P < 0.01). A clinicopathological-radiological model was developed based on these factors. The model showed good discrimination (concordance index, 0.798 [0.723-0.876]; P < 0.001) and was well-calibrated. CONCLUSIONS: The developed clinicopathological-radiological nomogram may assist clinicians in identifying patients at high risk of postoperative peritoneal metastasis.

Diffuse peritoneal carcinomatosis and Sister Mary Joseph nodule in ovarian carcinoma - exquisite demonstration of the peritoneal reflections on [18F]FDG PET/CT.

A case involving a 64-year-old woman with ovarian carcinoma on maintenance therapy who underwent 18-fluorodeoxyglucose positron emission tomography with computed tomography ([18F]FDG PET/CT) restaging due to rapid cancer antigen 125 (Ca-125) rise. This revealed recurrent disease within the pelvis and large volume, peritoneal carcinomatosis including an avid umbilical deposit, consistent with the rarely seen Sister Mary Joseph nodule (SMJN). This case elegantly demonstrates not only the anatomy of the peritoneal surfaces through avid disease deposition but also highlights the sensitive depiction of disease burden in peritoneal carcinomatosis, including the detection of rare manifestations such as SMJN.

Targeted delivery of cathepsin-activatable near-infrared fluorescence probe for ultrahigh specific imaging of peritoneal metastasis.

Inadequate cytoreductive surgery (CRS) has been identified as a prognostic factor for poor patient outcomes in cases of peritoneal metastasis. While imaging probes are used to identify peritoneal metastasis to facilitate CRS, many of these probes exhibit high background signals, resulting in a significant delay in achieving a satisfactory tumor-to-normal ratio (TNR) due to prolonged clearance time. In this study, we designed a novel fluorescent probe named Tras-AA-Cy NH2, which enables the relatively rapid imaging of subcutaneous tumors and peritoneal tumors while maintaining a high TNR. Mechanistically, Tras-AA-Cy NH2 exhibits selective targeting towards the Human epidermal growth factor receptor 2 on the surface of cancer cells. Following internalization, it undergoes enzymatic cleavage catalyzed by the overexpressed cathepsin, leading to the subsequent release of near-infrared fluorophores. Consequently, Tras-AA-Cy NH2 achieved a TNR of 7.8 at 6 h and 21.4 at 24 h in subcutaneous tumor mice. Even after 522 h of in vivo circulation, the TNR remained above 5, indicating an ultralong imaging time window. It is noteworthy that Tras-AA-Cy NH2 has demonstrated successful utilization for peritoneal tumor-specific imaging and further affirmed its tumor tissue-specific recognition capability using human resected tissues. In summary, these findings underscore the rational design of Tras-AA-Cy NH2 for visualizing peritoneal tumors.

CT-based deep learning model: a novel approach to the preoperative staging in patients with peritoneal metastasis.

Peritoneal metastasis (PM) is a frequent manifestation of advanced abdominal malignancies. Accurately assessing the extent of PM before surgery is essential for patients to receive optimal treatment. Therefore, we propose to construct a deep learning (DL) model based on enhanced computed tomography (CT) images to stage PM preoperatively in patients. All 168 patients with PM underwent contrast-enhanced abdominal CT before either open surgery or laparoscopic exploration, and peritoneal cancer index (PCI) was used to evaluate patients during the surgical procedure. DL features were extracted from portal venous-phase abdominal CT scans and subjected to feature selection using the Spearman correlation coefficient and LASSO. The performance of models for preoperative staging was assessed in the validation cohort and compared against models based on clinical and radiomics (Rad) signature. The DenseNet121-SVM model demonstrated strong patient discrimination in both the training and validation cohorts, achieving AUC was 0.996 in training and 0.951 validation cohort, which were both higher than those of the Clinic model and Rad model. Decision curve analysis (DCA) showed that patients could potentially benefit more from treatment using the DL-SVM model, and calibration curves demonstrated good agreement with actual outcomes. The DL model based on portal venous-phase abdominal CT accurately predicts the extent of PM in patients before surgery, which can help maximize the benefits of treatment and optimize the patient's treatment plan.

Evaluation of a polarization-enhanced laparoscopy prototype for improved intra-operative visualization of peritoneal metastases.

Despite careful staging, the accuracy for preoperative detection of small distant metastases remains poor, creating a clinical need for enhanced operative staging to detect occult peritoneal metastases. This study evaluates a polarization-enhanced laparoscopy (PEL) prototype and assesses its potential for label-free contrast enhancement of peritoneal metastases. This is a first-in-human feasibility study, including 10 adult patients who underwent standard staging laparoscopy (SSL) for gastrointestinal malignancy along with PEL. Image frames of all detectable peritoneal lesions underwent analysis. Using Monte Carlo simulations, contrast enhancement based on the color dependence of PEL (mPEL) was assessed. The prototype performed safely, yet with limitations in illumination, fogging of the distal window, and image co-registration. Sixty-five lesions (56 presumed benign and 9 presumed malignant) from 3 patients represented the study sample. While most lesions were visible under human examination of both SSL and PEL videos, more lesions were apparent using SSL. However, this was likely due to reduced illumination under PEL. When controlling for such effects through direct comparisons of integrated (WLL) vs differential (PEL) polarization laparoscopy images, we found that PEL imaging yielded an over twofold Weber contrast enhancement over WLL. Further, enhancements in the discrimination between malignant and benign lesions were achieved by exploiting the PEL color contrast to enhance sensitivity to tissue scattering, influenced primarily by collagen. In conclusion, PEL appears safe and easy to integrate into the operating room. When controlling for the degree of illumination, image analysis suggested a potential for mPEL to provide improved visualization of metastases.

68Ga-PSMA-11 PET/CT in a Case of Isolated Parietal Peritoneal Metastasis From Prostate Adenocarcinoma.

ABSTRACT: Isolated peritoneal metastasis of prostate cancer is extremely rare. We present 68Ga-PSMA-11 PET/CT findings in a case of isolated parietal peritoneal metastasis from prostate adenocarcinoma 35 months after radical prostatectomy. The peritoneal metastases showed multifocal intense PSMA uptake, but subtle structural abnormalities on 68Ga-PSMA-11 PET/CT. The patient was subsequently treated with androgen deprivation therapy. The peritoneal metastases progressed 25 months after the initiation of androgen deprivation therapy and were removed surgically. Histologic and immunohistochemical evaluation revealed metastatic prostate adenocarcinoma with treatment-related neuroendocrine differentiation. This case demonstrates the usefulness of 68Ga-PSMA-11 PET/CT in identifying atypical metastasis from prostate adenocarcinoma.

Efficacy of staging laparoscopy for resectable pancreatic cancer on imaging and the therapeutic effect of systemic chemotherapy for positive peritoneal cytology.

BACKGROUND: The frequency and prognosis of positive peritoneal washing cytology (CY1) in resectable pancreatic ductal adenocarcinoma (R-PDAC) remains unclear. The objective of this study was to identify the clinical implications of CY1 in R-PDAC and staging laparoscopy (SL). METHODS: We retrospectively analyzed 115 consecutive patients with R-PDAC who underwent SL between 2018 and 2022. Patients with negative cytology (CY0) received radical surgery after neoadjuvant chemotherapy, while CY1 patients received systemic chemotherapy and were continuously evaluated for cytology. RESULTS: Of the 115 patients, 84 had no distant metastatic factors, 22 had only CY1, and nine had distant metastasis. Multivariate logistic regression revealed that larger tumor size was an independent predictor of the presence of any distant metastatic factor (OR: 6.30, p = .002). Patients with CY1 showed a significantly better prognosis than patients with distant metastasis (MST: 24.6 vs. 18.9 months, p = .040). A total of 11 CY1 patients were successfully converted to CY-negative, and seven underwent conversion surgery. There was no significant difference in overall survival between patients with CY0 and those converted to CY-negative. CONCLUSION: SL is effective even for R-PDAC. The prognosis of CY1 patients converted to CY-negative is expected to be similar to that of CY0 patients.

Predictive performance of radiomics for peritoneal metastasis in patients with gastric cancer: a meta-analysis and radiomics quality assessment.

PURPOSE: The purpose of this meta-analysis is to systematically review the diagnostic performance of radiomic techniques in predicting peritoneal metastasis in patients with gastric cancer, and to evaluate the quality of current research. METHODS: We searched PubMed, Web of Science, EBSCO, Embase, and Cochrane databases for relevant studies up to April 3, 2023. Data extraction and quality evaluation were performed by two independent reviewers. Then we performed statistical analysis, including plotting the forest plot and summary receiver operating characteristic (SROC) curve, and source of heterogeneity analysis, through the MIDAS module in Stata 15. We performed meta-regression and subgroup analyses to analyze the sources of heterogeneity. Using the QUADAS-2 scale and the RQS scale to assess the quality of retrieved studies. RESULTS: Ten studies with 6199 patients were finally included in our meta-analysis. Pooled sensitivity and specificity were 0.77 (95% confidence interval [CI]: 0.66, 0.86), and 0.88 (95% CI 0.80, 0.93), respectively. The overall AUC was 0.89 (95% CI 0.86, 0.92). The heterogeneity of this meta-analysis was high, with I2 = 88% (95% CI 75,100). The result of meta-regression showed that QUADAS-2 results, RQS results and machine learning method led to heterogeneity in sensitivity and specificity (P < 0.05). Furthermore, the image segmentation area and the presence or absence of combined clinical factors were associated with sensitivity heterogeneity and specificity heterogeneity, respectively. CONCLUSION: Undoubtedly, radiomics has potential value in diagnosing peritoneal metastasis of gastric cancer, but the quality of current research is inconsistent, and more standardized and high-quality research is still needed in the future to achieve the transformation of radiomics results into clinical applications.

Noninvasive imaging evaluation of peritoneal recurrence and chemotherapy benefit in gastric cancer after gastrectomy: a multicenter study.

BACKGROUND: Peritoneal recurrence (PR) is the predominant pattern of relapse after curative-intent surgery in gastric cancer (GC) and indicates a dismal prognosis. Accurate prediction of PR is crucial for patient management and treatment. The authors aimed to develop a noninvasive imaging biomarker from computed tomography (CT) for PR evaluation, and investigate its associations with prognosis and chemotherapy benefit. METHODS: In this multicenter study including five independent cohorts of 2005 GC patients, the authors extracted 584 quantitative features from the intratumoral and peritumoral regions on contrast-enhanced CT images. The artificial intelligence algorithms were used to select significant PR-related features, and then integrated into a radiomic imaging signature. And improvements of diagnostic accuracy for PR by clinicians with the signature assistance were quantified. Using Shapley values, the authors determined the most relevant features and provided explanations to prediction. The authors further evaluated its predictive performance in prognosis and chemotherapy response. RESULTS: The developed radiomics signature had a consistently high accuracy in predicting PR in the training cohort (area under the curve: 0.732) and internal and Sun Yat-sen University Cancer Center validation cohorts (0.721 and 0.728). The radiomics signature was the most important feature in Shapley interpretation. The diagnostic accuracy of PR with the radiomics signature assistance was improved by 10.13-18.86% for clinicians ( P <0.001). Furthermore, it was also applicable in the survival prediction. In multivariable analysis, the radiomics signature remained an independent predictor for PR and prognosis ( P <0.001 for all). Importantly, patients with predicting high risk of PR from radiomics signature could gain survival benefit from adjuvant chemotherapy. By contrast, chemotherapy had no impact on survival for patients with a predicted low risk of PR. CONCLUSION: The noninvasive and explainable model developed from preoperative CT images could accurately predict PR and chemotherapy benefit in patients with GC, which will allow the optimization of individual decision-making.

Efficacy of HER2-Targeted Intraperitoneal 225Ac α-Pretargeted Radioimmunotherapy for Small-Volume Ovarian Peritoneal Carcinomatosis.

Epithelial ovarian cancer (EOC) is often asymptomatic and presents clinically in an advanced stage as widespread peritoneal microscopic disease that is generally considered to be surgically incurable. Targeted α-therapy with the α-particle-emitting radionuclide 225Ac (half-life, 9.92 d) is a high-linear-energy-transfer treatment approach effective for small-volume disease and even single cells. Here, we report the use of human epidermal growth factor receptor 2 (HER2) 225Ac-pretargeted radioimmunotherapy (PRIT) to treat a mouse model of human EOC SKOV3 xenografts growing as peritoneal carcinomatosis (PC). Methods: On day 0, 105 SKOV3 cells transduced with a luciferase reporter gene were implanted intraperitoneally in nude mice, and tumor engraftment was verified by bioluminescent imaging (BLI). On day 15, treatment was started using 1 or 2 cycles of 3-step anti-HER2 225Ac-PRIT (37 kBq/cycle as 225Ac-Proteus DOTA), separated by a 1-wk interval. Efficacy and toxicity were monitored for up to 154 d. Results: Untreated PC-tumor-bearing nude mice showed a median survival of 112 d. We used 2 independent measures of response to evaluate the efficacy of 225Ac-PRIT. First, a greater proportion of the treated mice (9/10 1-cycle and 8/10 2-cycle; total, 17/20; 85%) survived long-term compared with controls (9/27, 33%), and significantly prolonged survival was documented (log-rank [Mantel-Cox] P = 0.0042). Second, using BLI, a significant difference in the integrated BLI signal area to 98 d was noted between controls and treated groups (P = 0.0354). Of a total of 8 mice from the 2-cycle treatment group (74 kBq total) that were evaluated by necropsy, kidney radiotoxicity was mild and did not manifest itself clinically (normal serum blood urea nitrogen and creatinine). Dosimetry estimates (relative biological effectiveness-weighted dose, where relative biological effectiveness = 5) per 37 kBq administered for tumors and kidneys were 56.9 and 16.1 Gy, respectively. One-cycle and 2-cycle treatments were equally effective. With immunohistology, mild tubular changes attributable to α-toxicity were observed in both therapeutic groups. Conclusion: Treatment of EOC PC-tumor-bearing mice with anti-HER2 225Ac-PRIT resulted in histologic cures and prolonged survival with minimal toxicity. Targeted α-therapy using the anti-HER2 225Ac-PRIT system is a potential treatment for otherwise incurable EOC.

Peritoneal Carcinomatosis From Metastatic Prostate Cancer Identified on 68 Ga-Prostate-Specific Membrane Antigen PET/CT.

ABSTRACT: A 69-year-old man with locally advanced prostate adenocarcinoma (Gleason score 9), who had completed hormone therapy and definitive radiotherapy, presented to hospital with abdominal pain and distension. A CT scan of the abdomen and pelvis revealed ascites and extensive peritoneal/omental nodules. Serum prostate-specific antigen was not raised (0.07 µg/L). 68 Ga-prostate-specific membrane antigen (PSMA) PET/CT demonstrated PSMA-avid disease in the prostate and widespread PSMA-avid peritoneal/omental and liver metastases but with no PSMA-avid bony metastases. Peritoneal nodule biopsy confirmed metastatic prostate cancer.