Salivary toxicity from PSMA-targeted radiopharmaceuticals: What we have learned and where we are going

Clinical trials of prostate-specific membrane antigen (PSMA) targeted radiopharmaceuticals have shown encouraging results. Some agents, like lutetium-177 [177Lu]Lu-PSMA-617 ([177Lu]Lu-PSMA-617), are already approved for late line treatment of metastatic castration-resistant prostate cancer (mCRPC). Projections are for continued growth of this treatment modality; [177Lu]Lu-PSMA-617 is being studied both in earlier stages of disease and in combination with other anti-cancer therapies. Further, the drug development pipeline is deep with variations of PSMA-targeting radionuclides, including higher energy alpha particles conjugated to PSMA-honing vectors. It is safe to assume that an increasing number of patients will be exposed to PSMA-targeted radiopharmaceuticals during the course of their cancer treatment. In this setting, it is important to better understand and mitigate the most commonly encountered toxicities. One particularly vexing side effect is xerostomia. In this review, we discuss the scope of the problem, inventories to better characterize and monitor this troublesome side effect, and approaches to preserve salivary function and effectively palliate symptoms. This article aims to serve as a useful reference for prescribers of PSMA-targeted radiopharmaceuticals, while also commenting on areas of missing data and opportunities for future research.

Critical updates in neuroendocrine tumors: Version 9 American Joint Committee on Cancer staging system for gastroenteropancreatic neuroendocrine tumors

The American Joint Committee on Cancer (AJCC) staging system for all cancer sites, including gastroenteropancreatic neuroendocrine tumors (GEP-NETs), is meant to be dynamic, requiring periodic updates to optimize AJCC staging definitions. This entails the collaboration of experts charged with evaluating new evidence that supports changes to each staging system. GEP-NETs are the second most prevalent neoplasm of gastrointestinal origin after colorectal cancer. Since publication of the AJCC eighth edition, the World Health Organization has updated the classification and separates grade 3 GEP-NETs from poorly differentiated neuroendocrine carcinoma. In addition, because of major advancements in diagnostic and therapeutic technologies for GEP-NETs, AJCC version 9 advocates against the use of serum chromogranin A for the diagnosis and monitoring of GEP-NETs. Furthermore, AJCC version 9 recognizes the increasing role of endoscopy and endoscopic resection in the diagnosis and management of NETs, particularly in the stomach, duodenum, and colorectum. Finally, T1NXM0 has been added to stage I in these disease sites as well as in the appendix.

Targeted Alpha-Particle Therapy: A Review of Current Trials

Radiopharmaceuticals are rapidly developing as a field, with the successful use of targeted beta emitters in neuroendocrine tumors and prostate cancer serving as catalysts. Targeted alpha emitters are in current development for several potential oncologic indications. Herein, we review the three most prevalently studied conjugated/chelated alpha emitters (²²⁵actinium, ²¹²lead, and ²¹¹astatine) and focus on contemporary clinical trials in an effort to more fully appreciate the breadth of the current evaluation. Phase I trials targeting multiple diseases are now underway, and at least one phase III trial (in selected neuroendocrine cancers) is currently in the initial stages of recruitment. Combination trials are now also emerging as alpha emitters are integrated with other therapies in an effort to create solutions for those with advanced cancers. Despite the promise of targeted alpha therapies, many challenges remain. These challenges include the development of reliable supply chains, the need for a better understanding of the relationships between administered dose and absorbed dose in both tissue and tumor and how that predicts outcomes, and the incomplete understanding of potential long-term deleterious effects of the alpha emitters. Progress on multiple fronts is necessary to bring the potential of targeted alpha therapies into the clinic.

Clinical utility of somatostatin receptor positron emission tomography imaging biomarkers for characterization of meningioma among incidental central nervous system lesions

OBJECTIVES

Somatostatin receptor (SSTR) PET imaging is utilized with increasing frequency in the clinical management of neuroendocrine tumors. Incidental PET-avid CNS lesions are commonly noted and presumed to be meningiomas. However, SSTR PET lacks specificity for meningioma identification. This study aimed to clarify the role of SSTR-based imaging in the classification of incidental CNS lesions based on current clinical practice.

METHODS

Patients who underwent both Ga-68-DOTATATE PET and brain MRI and had an incidental CNS lesion identified with a radiographic prediction of meningioma via one (discordant prediction) or both (concordant prediction) imaging modalities were retrospectively analyzed. Imaging indication, semiquantitative measures, and clinical history were recorded.

RESULTS

Among 48 patients with a CNS lesion identified on both imaging modalities, most scans were performed for a history of neuroendocrine tumor (64.6%). Cases with concordant lesion-type prediction of meningioma between imaging modalities ( N = 24) displayed a significantly higher SUV max (median 7.9 vs. 4.0; P = 0.008) and Krenning score (median 3.0 vs. 2.0; P = 0.005) on Ga-68-DOTATATE PET compared with cases with a discordant prediction of meningioma ( N = 24). In cases with lower SUV max values, Ga-68-DOTATATE was more likely to discordantly predict meningioma without agreement by the corresponding MRI. Prior cranial radiation or use of somatostatin mimetics did not affect quantitative radiographic measures, and MRI-based tumor size was similar across groups.

CONCLUSION

Lesions with increased avidity may be more confidently predicted as meningioma in Ga-68-DOTATATE PET scans, whereas there is more discrepancy in prediction among low SUV cases.

Health-related quality of life and pain outcomes with [177Lu]Lu-PSMA-617 plus standard of care versus standard of care in patients with metastatic castration-resistant prostate cancer (VISION): a multicentre, open-label, randomised, phase 3 trial

BACKGROUND

In VISION, the prostate-specific membrane antigen (PSMA)-targeted radioligand therapy lutetium-177 [177Lu]Lu-PSMA-617 (vipivotide tetraxetan) improved radiographic progression-free survival and overall survival when added to protocol-permitted standard of care in patients with metastatic castration-resistant prostate cancer. Here, we report additional health-related quality of life (HRQOL), pain, and symptomatic skeletal event results.

METHODS

This multicentre, open-label, randomised, phase 3 trial was conducted at 84 cancer centres in nine countries in North America and Europe. Eligible patients were aged 18 years or older; had progressive PSMA-positive metastatic castration-resistant prostate cancer; an Eastern Cooperative Oncology Group (ECOG) performance status score of 0-2; and had previously received of at least one androgen receptor pathway inhibitor and one or two taxane-containing regimens. Patients were randomly assigned (2:1) to receive either [177Lu]Lu-PSMA-617 plus protocol-permitted standard of care ([177Lu]Lu-PSMA-617 group) or standard of care alone (control group) using permuted blocks. Randomisation was stratified by baseline lactate dehydrogenase concentration, liver metastases, ECOG performance status, and androgen receptor pathway inhibitor inclusion in standard of care. Patients in the [177Lu]Lu-PSMA-617 group received intravenous infusions of 7·4 gigabecquerel (GBq; 200 millicurie [mCi]) [177Lu]Lu-PSMA-617 every 6 weeks for four cycles plus two optional additional cycles. Standard of care included approved hormonal treatments, bisphosphonates, and radiotherapy. The alternate primary endpoints were radiographic progression-free survival and overall survival, which have been reported. Here we report the key secondary endpoint of time to first symptomatic skeletal event, and other secondary endpoints of HRQOL assessed with the Functional Assessment of Cancer Therapy-Prostate (FACT-P) and EQ-5D-5L, and pain assessed with the Brief Pain Inventory-Short Form (BPI-SF). Patient-reported outcomes and symptomatic skeletal events were analysed in all patients who were randomly assigned after implementation of measures designed to reduce the dropout rate in the control group (on or after March 5, 2019), and safety was analysed according to treatment received in all patients who received at least one dose of treatment. This trial is registered with ClinicalTrials.gov, NCT03511664, and is active but not recruiting.

FINDINGS

Between June 4, 2018, and Oct 23, 2019, 831 patients were enrolled, of whom 581 were randomly assigned to the [177Lu]Lu-PSMA-617 group (n=385) or control group (n=196) on or after March 5, 2019, and were included in analyses of HRQOL, pain, and time to first symptomatic skeletal event. The median age of patients was 71 years (IQR 65-75) in the [177Lu]Lu-PSMA-617 group and 72·0 years (66-76) in the control group. Median time to first symptomatic skeletal event or death was 11·5 months (95% CI 10·3-13·2) in the [177Lu]Lu-PSMA-617 group and 6·8 months (5·2-8·5) in the control group (hazard ratio [HR] 0·50, 95% CI 0·40-0·62). Time to worsening was delayed in the [177Lu]Lu-PSMA-617 group versus the control group for FACT-P score (HR 0·54, 0·45-0·66) and subdomains, BPI-SF pain intensity score (0·52, 0·42-0·63), and EQ-5D-5L utility score (0·65, 0·54-0·78). Grade 3 or 4 haematological adverse events included decreased haemoglobin (80 [15%] of 529 assessable patients who received [177Lu]Lu-PSMA-617 plus standard of care vs 13 [6%] of 205 who received standard of care only), lymphocyte concentrations (269 [51%] vs 39 [19%]), and platelet counts (49 [9%] vs five [2%]). Treatment-related adverse events leading to death occurred in five (1%) patients who received [177Lu]Lu-PSMA-617 plus standard of care (pancytopenia [n=2], bone marrow failure [n=1], subdural haematoma [n=1], and intracranial haemorrhage [n=1]) and no patients who received standard of care only.

INTERPRETATION

[177Lu]Lu-PSMA-617 plus standard of care delayed time to worsening in HRQOL and time to skeletal events compared with standard of care alone. These findings support the use of [177Lu]Lu-PSMA-617 in patients with metastatic castration-resistant prostate cancer who received previous androgen receptor pathway inhibitor and taxane treatment.

FUNDING

Advanced Accelerator Applications (Novartis).

A VISION Substudy of Reader Agreement on 68Ga-PSMA-11 PET/CT Scan Interpretation to Determine Patient Eligibility for 177Lu-PSMA-617 Radioligand Therapy

⁶⁸Ga-gozetotide (⁶⁸Ga-PSMA-11) is used to identify prostate-specific membrane antigen (PSMA)-positive tumors on PET scans. In the VISION study, ⁶⁸Ga-PSMA-11 was used to determine the eligibility of patients with metastatic castration-resistant prostate cancer for treatment with ¹⁷⁷Lu-vipivotide tetraxetan (¹⁷⁷Lu-PSMA-617), based on predefined read criteria. This substudy aimed to investigate the interreader variability and intrareader reproducibility of visual assessments of ⁶⁸Ga-PSMA-11 PET/CT scans using the VISION read criteria and evaluate the agreement between read results for this and the VISION study. Methods: In VISION, ⁶⁸Ga-PSMA-11 PET/CT scans were centrally read as inclusion cases if they had at least 1 PSMA-positive lesion and no PSMA-negative lesions that fulfilled the exclusion criteria. In this substudy, 125 PET/CT scans (75 inclusion and 50 exclusion cases) were randomly selected from VISION and retrospectively assessed by 3 independent central readers. A random subset of 20 cases (12 inclusion and 8 exclusion cases) was recoded for assessment of intrareader reproducibility. Classification of cases as inclusion or exclusion cases was based on the VISION read criteria. Overall interreader variability was assessed by Fleiss κ-statistics, and pairwise variability and intrareader reproducibility were assessed by Cohen κ-statistics. Results: For interreader variability, the readers agreed on 77% of cases (overall average agreement rate, 0.85; Fleiss κ, 0.60 [95% CI, 0.50-0.70]). The pairwise agreement rate was 0.82, 0.88, and 0.84, and the corresponding Cohen κ was 0.54 (95% CI, 0.38-0.71), 0.67 (95% CI, 0.52-0.83), and 0.59 (95% CI, 0.43-0.75), respectively. For intrareader reproducibility, the agreement rate was 0.90, 0.90, and 0.95, and the corresponding Cohen κ was 0.78 (95% CI, 0.49-0.99), 0.76 (95% CI, 0.46-0.99), and 0.89 (95% CI, 0.67-0.99), respectively. The number of actual VISION inclusion cases out of the total number of cases scored as inclusion in this substudy was 71 of 93 (agreement rate, 0.76; 95% CI, 0.66-0.85) for reader 1, 70 of 88 (0.80; 0.70-0.87) for reader 2, and 73 of 96 (0.76; 0.66-0.84) for reader 3. All readers agreed on 66 of 75 VISION inclusion cases. Conclusion: Moderate-to-substantial interreader agreement and substantial-to-almost perfect intrareader reproducibility for ⁶⁸Ga-PSMA-11 PET/CT scan assessment using the VISION read criteria were observed. The read rules applied in VISION can be readily learned and demonstrate good reproducibility.

Prognostic value of C-11 choline PET/CT scan in patients with metastatic castration resistant prostate cancer (m-CRPC) undergoing treatment with radium-223

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Background: Radium-223 (Ra-223) has been approved for the treatment of metastatic castration resistant prostate cancer (mCRPC) with predominantly osseous metastases. PSA flare phenomenon with Ra-223 limits the use of PSA as a prognostic tool to predict treatment response. Currently, there is a lack of diagnostic tools to predict treatment response to Ra-223. Therefore, we sought to investigate the role of mid-treatment C-11 choline PET/CT scan in predicting overall response to Ra-223. Methods: In a single institute retrospective study, we identified 32 patients who were treated with a full course of 4-6 cycles of Ra-223 and were evaluated with both PSA and C-11 choline PET scan before treatment, at mid-treatment, and after a complete course of Ra-223 between 2013 – 2018. Ra-223 was used as salvage therapy for their predominant bone disease after failing chemotherapy and 2nd generation hormone therapy. Blind repeat radiographic evaluation of patients’ scans was performed by a radiologist specialized in nuclear radiology. Favorable response was defined by achieving partial response or stable disease on imaging, while unfavorable response was defined by showing progressive disease on imaging. Results: Mean age (±SD) at starting Radium223 was 67.6 (±7.1) years, median (IQR) primary Gleason score was 9 (8-9), and median (IQR) pretreatment PSA was 13.5 (5.4-39.6) ng/ml. 78% of the patients (n=25) completed 6 cycles of Ra-223, 15% of the patients (n=5) completed 5 cycles, and 6% (n=2) received only 4 cycles. At mid-treatment scanning, 25% of the patients (n=8) showed favorable response (Group A), while 75% of the patients (n=24) showed unfavorable response (B). After a complete course of treatment, 62.5% of patients (n=5) in Group (A) continued to show favorable response, while only 8.3% of patients (n=2) in Group (B) showed favorable response (p-value= 0.0023). Conclusions: Mid-treatment evaluation with C-11 choline PET/CT scan can predict overall response to Radium 223. Patients with progressive disease at mid-treatment evaluation are very likely not going to respond to further treatment. Further studies and clinical trials are warranted.

Survival patterns based on site-specific visceral metastasis in patients with metastatic prostate cancer: Are outcomes of visceral metastases the same?

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Background: Metastatic visceral involvement in prostate cancer patients conveys a poor prognosis. Survival patterns of site-specific visceral metastasis are poorly understood. Here, we sought to investigate survival patterns in prostate cancer patients according to their first detected site of visceral metastasis. Methods: Retrospectively, we identified 200 patients with visceral metastatic prostate cancer. Patients were divided into three groups according to first site detected with visceral metastases; first-site lung metastases, first-site brain metastases, and first-site liver metastases. Visceral metastases were detected on either conventional imaging (CT/MRI), metabolic imaging (C-11 choline), or PSMA PET-CT scan. Follow up duration of our study was 80 months. Results: Clinicopathological variables are shown. The K-M curve of overall survival of the entire cohort suggests better survival patterns in patients with first-site lung metastases compared to patients with first-site brain or liver metastases (p<0.0001). In subset analysis of patients with CRPC, the K-M curve of overall survival, which demonstrates better survival outcomes in patients with first-site lung metastases in comparison with patients with first-site brain or liver metastases (p<0.0001). Conclusions: Our data suggests that prostate cancer patients with visceral metastatic disease have different survival patterns according to the first site detected with visceral metastasis. In our cohort, patients with first-site lung metastasis demonstrated better survival outcomes than patients with first-site brain or liver metastasis. Further studies are warranted. [Table: see text]

High-volume mCRPC is associated with decreased cancer specific survival in patients on second-generation hormone therapy in the post docetaxel setting

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Background: In the setting of disease progression of metastatic castrate resistant prostate cancer (mCRPC) on docetaxel, abiraterone acetate (AA) and enzalutamide are two commonly used second line therapies with data demonstrating survival benefits. Less is known about patient specific factors that contribute to success with these therapies. The objective of this study is to improve patient selection for post-docetaxel second generation hormone therapy (AA or enzalutamide) by evaluating whether overall metastatic burden is associated with treatment response in this setting. Methods: By retrospective chart review, patients with mCRPC treated with AA or enzalutamide following docetaxel failure (defined as PSA rise and radiographic progression) were identified. Patients were categorized into low volume and high volume metastatic disease based on the number of pre-treatment metastatic lesions; where low volume disease describes patients with ≤ 5 metastatic lesions (e.g. oligometastatic disease), and high volume disease represents patients with > 5 individual lesions. The primary endpoint was cancer-specific mortality and the secondary endpoint was radiographic progression free survival. Median follow-up time was 29.5 months. Results: 75 patients were identified and included in our analysis: 39 with high volume metastatic disease, and 36 with low volume metastatic disease. Baseline characteristics of age and pre-treatment ECOG were not statistically different between these groups. Pre-treatment high-volume disease burden was significantly associated with increased risk of radiographic disease progression (HR 4.21, 95%CI 1.97-8.99, p < 0.0001) and cancer specific mortality (HR 5.84, 95% CI 1.58-21.53, p = 0.0026) during treatment with second generation androgen deprivation therapy. Conclusions: High volume metastatic disease burden is associated with significantly increased cancer specific mortality and decreased progression free survival for patients on second line therapy with AA or enzalutamide following docetaxel treatment failure.

Factors associated with poor survival outcomes in patients with prostate cancer (PCa) with radiographic disease progression in the setting of low PSA

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Background: Recent studies, including a post-hoc analysis of the ARCHES trial, highlight radiographic disease progression (rDP) occurring without concordant rise in prostate specific antigen (PSA). In a previous study by our group, we reported that almost 40% of patients on 2nd generation hormone therapy experience rDP with non-rising PSA and have poor survival outcomes. The current analysis more specifically focuses on the subgroup of patients with rDP occurring at low PSA (<0.5 ng/dL) and describes factors associated with poorer survival outcomes in this patient population. Methods: In a single institution study, we reviewed the prospectively maintained Mayo Clinic C-11 Choline PET registry for patients treated between 2011 and 2021, who experienced rDP at low PSA (value < 0.5 ng/mL). Disease progression on C-11 choline PET was confirmed by either tissue biopsy or subsequent response to therapy. We investigated factors associated with poor cancer-specific survival outcomes in univariable and multivariable cox regression analyses. Results: In total, 220 (16%) patients experiencing rDP at low PSA were identified. Median (IQR) age at rDP was 67.91 (61.10 – 73.87) yrs., median (IQR) primary Gleason score was 9 (7-9), and median (IQR) PSA was 0.17 (0 – 0.32) ng/ml. 75% of the patients (n=166) had CRPC disease status at time of rDP. Prior systemic treatments included 2nd generation HT in 18% (n= 40) and chemotherapy in 31% (n=70). Sites of rDP were divided into 7% local (n=16), 42% lymph nodes (n=91), 43% bone (n=95), and 8% visceral metastases (n=18). Over a median follow-up duration of 55 months, 46% of patients (n=100) reported death. Factors associated with poor survival outcomes are demonstrated in the table and include age at rDP, CRPC status, and disease location (P-value <0.05). Conclusions: We found that radiographic disease progression commonly occurs at low PSA (<0.5 ng/mL). CRPC-disease status and the development of visceral metastases are associated with particularly poor survival outcomes. To identify early progression, monitoring with imaging may be warranted, even in the patients with low PSA. [Table: see text]

Effect of early PSA decline after starting second-generation hormone therapy in the post-docetaxel setting on cancer-specific survival in metastatic castrate-resistant prostate cancer

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Background: The objective of this study is to evaluate the prognostic value of early PSA decline following initiation of second-generation hormone therapy (2nd HT), namely abiraterone acetate or enzalutamide, in the post-chemotherapy setting in patients with metastatic castrate-resistant prostate cancer (mCRPC). Methods: We retrospectively identified 75 m-CRPC patients treated with 2nd HT following docetaxel failure (defined as PSA rise and radiographic progression). Patients were categorized into two groups based on first PSA within 3 months after initiation of therapy: PSA reduction ≥ 50% (Group A) and PSA reduction < 50% (Group B). The primary endpoint was cancer-specific mortality and the secondary endpoint was radiographic progression free survival. Results: There were 75 patients (52 in group A, 23 in group B) in the analytic cohort. Baseline clinical and demographic characteristics, including median age, primary Gleason score risk group, median pre-treatment PSA, disease burden, site of metastases, and pre-treatment ECOG score were not statistically different between the two groups. PSA reduction ≥50% was significantly associated with decreased risk of radiographic disease progression (HR 0.41, 95%CI 0.21-0.80, p = 0.0113) as well as decreased risk of cancer-specific mortality (HR 0.29, 95%CI 0.09-0.87, p = 0.0325). Conclusions: PSA reduction ≥50% within 3 months of starting 2nd HT for patients with mCRPC who have failed first-line docetaxel is associated with significantly improved 3-year cancer-specific mortality and progression free survival. Our data supports the use of PSA as an early prognosticating marker for patient outcomes on this second line therapy. [Table: see text]

Incorporating radioligand therapy in clinical practice in the United States for patients with prostate cancer

Prostate cancer (PC) is the second most commonly diagnosed cancer in the United States. Advanced PC evolves to metastatic castration-resistant PC (mCRPC). Theranostics combining prostate-specific membrane antigen-targeted positron emission tomography imaging and radioligand therapy (RLT) represents a precision medicine approach to PC treatment. With the recent approval of lutetium Lu 177 (¹⁷⁷Lu) vipivotide tetraxetan for men with mCRPC, the utilization of RLT will increase. In this review, we suggest a framework for incorporating RLT for PC into clinical practice. A search of PubMed and Google Scholar was performed using keywords related to PC, RLT, prostate-specific membrane antigen, and novel RLT centers. The authors also provided opinions based on their clinical experience. The setup and operation of an RLT center requires the diligence and cooperation of a well-trained multidisciplinary team committed to patient safety and clinical efficacy. Administrative systems should ensure that treatment scheduling, reimbursement, and patient monitoring are efficient. For optimal outcomes, the clinical care team must have an organizational plan that delineates the full range of required tasks. Establishing new RLT centers for treatment of PC is possible with appropriate multidisciplinary planning. We provide an overview of the key elements to consider when establishing a safe, efficient, and high-quality RLT center.

Characterizing bone metastases and skeletal-related events in patients with well-differentiated neuroendocrine neoplasms utilizing Ga68-DOTATE PET

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Background: Tumors of neuroendocrine origin are a rare, heterogenous group of neoplasms. Neuroendocrine neoplasms (NENs) are categorized by site of origin, differentiation status, and by grade (Ki-67 expression and/or mitotic rate), with prognostic variability accordingly. These tumors frequently metastasize to bone, with reported incidence between 6-12% by older SSTR imaging. Our study evaluates patients with well-differentiated tumors of neuroendocrine origin to determine the incidence of osseous metastases when evaluated with higher-sensitivity Ga68 DOTATATE PET scans. The study characterizes the clinical features. Methods: This study was performed at a single, 3-site, US tertiary-care institution. IRB approval was obtained. An automated data extraction tool was used to mine the electronic medical record by searching all positron emission tomography (PET) studies for keywords. Identified scans had to include a combination of the following keywords: “Dotatate” AND “met*” or “lesion” AND “bone” or “osse*” or “skel*”. The individual medical records from the generated report were reviewed to include only patients with 1) well-differentiated NETs of GI and pancreatic origin, lung carcinoid, paraganglioma/pheochromocytoma, or other/unknown primary site, and 2) patients with confirmed osseous metastatic disease. Patient data was entered into a database and evaluated in aggregate. Results: 1,948 PET scans of 1,473 patients were extracted from the EMR, from which 424 patients were identified for inclusion; scans were performed between 5/2018 and 5/2021. Calculated incidence of bone metastasis by Ga68 DOTATATE PET was 28.8%. Median age of included population was 61 years (range 14-92), 49.5% being male. Site of origin was 47.2% bowel NET, 18.9% pancreatic NET, 10.8% lung carcinoid, 10.6% paraganglioma/pheochromocytoma, 2.1% other site, and 10.4% unknown primary. Majority of patients were asymptomatic (64.0%), had sclerotic appearance (76.7%), Krenning 4 (71.4%), and >3 sites (68.3%) of osseous disease. 94.6% of the population had disease of the axial skeleton; 65.6% appendicular. Only 57 patients (13.4%) with osseous disease suffered a fracture, despite metastases at high-risk sites. Fracture occurred at disproportionately low rates in NETs originating in bowel (22.8% of fractures), with proportionately higher rates among pancreatic NETS and paragangliomas/pheochromocytomas (31.6% and 22.8%, respectively). Fractures occurred at proportionately higher rates in higher-grade disease compared to low-grade. Conclusions: Osseous metastatic disease in well-differentiated NENs is evident at much higher rates when imaging with Ga68 DOTATATE PET compared with previously reported data. Nevertheless, fracture occurred at a low rate, suggesting that these patients are at a relatively low risk for skeletal-related events.

Status of PSMA-targeted radioligand therapy in prostate cancer: current data and future trials

Metastatic prostate cancer continues to be an incurable disease. Despite all the novel therapies approved in the past two decades, overall patient outcomes remain relatively poor, and these patients die on a regular basis. Clearly, improvements in current therapies are needed. Prostate-specific membrane antigen (PSMA) is a target for prostate cancer given its increased expression on the surface of the prostate cancer cells. PSMA small molecule binders include PSMA-617 and PSMA-I&T and monoclonal antibodies such as J591. These agents have been linked to different radionuclides including beta-emitters such as lutetium-177 and alpha-emitters such as actinium-225. The only regulatory-approved PSMA-targeted radioligand therapy (PSMA-RLT) to date is lutetium-177-PSMA-617 in the setting of PSMA-positive metastatic castration-resistant prostate cancer that has failed androgen receptor pathway inhibitors and taxane chemotherapy. This approval was based on the phase III VISION trial. Many other clinical trials are evaluating PSMA-RLT in various settings. Both monotherapy and combination studies are underway. This article summarizes pertinent data from recent studies and provides an overview of human clinical trials in progress. The field of PSMA-RLT is rapidly evolving, and this therapeutic approach will likely play an increasingly important role in the years to come.

Radiographic paradoxical response in metastatic castrate-resistant prostate cancer (mCRPC) managed with new generation anti-androgens: a retrospective analysis

BACKGROUND

Prostatic specific antigen (PSA) has well-recognized limitations as a marker for treatment response and disease progression. Post hoc analysis of the PREVAIL trial reported 24.5% of chemotherapy naïve metastatic castration-resistant prostate cancer (mCRPC) patients on enzalutamide had radiographic progression on conventional imaging with nonrising PSA. In this study, we sought to study the discordance of imaging with PSA kinetics in mCRPC patients on second generation anti-androgens (SGA) post-chemotherapy using combined conventional imaging, and new generation imaging in the form of C-11 choline positron emission tomography/computed tomography (C[11] choline PET/CT) scan.

METHODS

We retrospectively reviewed the medical records of 123 patients with mCRPC treated with SGA (Abiraterone or Enzalutamide) after docetaxel between 2016 and 2019. Patients underwent PSA testing, and C[11] choline PET/CT scan at baseline level before starting treatment with SGA, then every 3-6 months as part of their follow up evaluation. Loss of response to SGA was defined by increase in corrected maximum standardized uptake value (SUVmax) of pretreatment lesions on C-11 Choline PET/CT, and/or development of new lesions. Suspicious new lesions were confirmed by biopsy and/or conventional imaging.

RESULTS

We identified 123 mCRPC patients who received SGA (Abiraterone, n = 106; Enzalutamide, n = 17) after docetaxel. Median duration of therapy was 13.9 months (interquartile range: 8.75-21.14). Approximately 43% (n = 53) of subjects in this study exhibited an increase in choline avidity while on SGA. Of this group, 60.4% of patients experienced a parallel rise in PSA (Group-A), whereas 39.6% displayed a paradoxical response (PR) (Group-B), defined as increased choline avidity combined with stable or down-trending PSA. Median PSA at time of increase in choline avidity was 3.1 ng/ml for Group-A, and 1.3 ng/ml for Group-B (p = 0.0176). Median SUVmax was similar in both groups (4.9 for Group-A, 4.6 for Group-B; p = 0.6072). The median time for increase in choline avidity was 9.5 versus 3.9 months for Group-A versus Group-B, respectively (Log-Rank = 0.0063).

CONCLUSION

Nearly 40% of mCRPC patients placed on SGA post docetaxel chemotherapy will exhibit paradoxical responses to therapy, therefore, warranting close follow up with imaging. C-11 choline PET/CT imaging is a useful tool that can help in early predication of disease progression or treatment failure.

The impact of genetic aberrations on response to radium-223 treatment for castration-resistant prostate cancer with bone metastases

BACKGROUND

Radium (Ra)-223 is an established treatment option for patients with metastatic castrate-resistant prostate cancer (mCRPC) who have symptomatic bone metastases without soft tissue disease. Studies have indicated genetic aberrations that regulate DNA damage response (DDR) in prostate cancer can increase susceptibility to treatments such as poly ADP-ribose polymerase inhibitors and platinum-based therapies. This study aims to evaluate mCRPC response to Ra-223 stratified by tumor genomics.

METHODS

This is a retrospective study of mCRPC patients who received Ra-223 and genetic testing within the Mayo Clinic database (Arizona, Florida, and Minnesota) and Tulane Cancer Center. Patient demographics, genetic aberrations, treatment responses in terms of alkaline phosphatase (ALP) and prostate-specific antigen (PSA), and survival were assessed. Primary end points were ALP and PSA response. Secondary end points were progression-free survival (PFS) and overall survival (OS) from time of first radium treatment.

RESULTS

One hundred and twenty-seven mCRPC patients treated with Ra-223 had germline and/or somatic genetic sequencing. The median age at time of diagnosis and Ra-223 treatment was 61.0 and 68.6 years, respectively. Seventy-nine (62.2%) had Gleason score ≥ 8 at time of diagnosis. 50.4% received prior docetaxel, and 12.6% received prior cabazitaxel. Notable alterations include TP53 (51.7%), BRCA 1/2 (15.0%), PTEN (13.4%), ATM (11.7%), TMPRSS2-ERG (8.2%), RB deletion (3.4%), and CDK12 (1.9%). There was no significant difference in ALP or PSA response among the different genetic aberrations. Patients with a TMPRSS2-ERG mutation exhibited a trend toward lower OS 15.4 months (95% confidence interval [CI] 10.0-NR) versus 26.8 months (95% CI 20.9-35.1). Patients with an RB deletion had a lower PFS 6.0 months (95% CI 1.28-NR) versus 9.0 months (95% CI 7.3-11.1) and a lower OS 13.9 months (95% CI 5.2-NR) versus 26.5 months (95% CI 19.8-33.8).

CONCLUSIONS

Among mCRPC patients treated with Ra-223 at Mayo Clinic and Tulane Cancer Center, we did not find any clear negative predictors of biochemical response or survival to treatment. TMPRSS2-ERG and RB mutations were associated with a worse OS. Prospective studies and larger sample sizes are needed to determine the impact of genetic aberrations in response to Ra-223.

[177Lu]Lu-PSMA-617 in PSMA-positive metastatic castration-resistant prostate cancer: Prior and concomitant treatment subgroup analyses of the VISION trial

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Background: In the phase 3 VISION trial, targeted radioligand therapy with lutetium (177Lu) vipivotide tetraxetan ([177Lu]Lu-PSMA-617; 177Lu-PSMA-617) significantly prolonged radiographic progression-free survival (rPFS) and overall survival (OS) when added to standard of care (SoC) in patients with advanced prostate-specific membrane antigen (PSMA) PET-positive metastatic castration-resistant prostate cancer. Benefits were consistent across most pre-specified subgroups. In this post hoc exploratory analysis, we examined rPFS and OS in the context of prior and concomitant cancer-directed treatments. Methods: In VISION, adult patients previously treated with at least 1 androgen receptor pathway inhibitor (ARPI) and 1–2 taxane regimens were randomized 2:1 to 177Lu-PSMA-617 (7.4 GBq Q6W, up to 6 cycles) + SoC or SoC alone. Protocol-permitted SoC excluded cytotoxic chemotherapy, systemic radioisotopes, immunotherapy, or other investigational drugs. Exploratory subgroup analyses of rPFS and OS were performed by: number of prior ARPIs; taxane regimens; non-taxane regimens and immunotherapies; prior treatment with bone-sparing agents; 223Ra and PARP inhibitors; and concomitant treatment with ARPIs, radiation therapy, and bone-sparing agents. Results: Prior and concomitant treatments were generally well balanced between study groups (Table). rPFS and OS benefits with 177Lu-PSMA-617 were consistent across all prior treatment subgroups. Notably, there were benefits in patients who had not received a second prior taxane. There were also consistent benefits regardless of concomitant systemic and radiation therapy as part of SoC. Conclusions: The clinical efficacy of 177Lu-PSMA-617 was observed regardless of prior treatment or SoC chosen, suggesting that disease biology rather than prior and concomitant treatment context drives outcomes. Small differences in outcomes between subgroups may warrant further study to understand better the predictors of improved clinical benefit. Clinical trial information: NCT03511664. [Table: see text]

[68Ga]Ga-PSMA-11 PET baseline imaging as a prognostic tool for clinical outcomes to [177Lu]Lu-PSMA-617 in patients with mCRPC: A VISION substudy

5002

Background: In the phase 3 VISION study, gallium (68Ga) gozetotide (68Ga-PSMA-11) PET/CT imaging was used to determine eligibility for lutetium (177Lu) vipivotide tetraxetan (177Lu-PSMA-617). Given that 177Lu-PSMA-617 targets PSMA, we assessed the association between quantitative PSMA imaging parameters and treatment outcomes. Methods: In VISION, adults with mCRPC with ≥ 1 PSMA-positive (+) and no PSMA-negative lesions meeting the exclusion criteria were enrolled. In this sub-study, the association between imaging data from pre-enrollment 68Ga-PSMA-11 PET/CT scans of pts in the 177Lu-PSMA-617 group and clinical outcomes was assessed. Imaging data meeting quality requirements were analyzed for 548/551 pts. PSMA expression was quantified by 5 PET parameters: PSMA+ lesions by region, mean standardized uptake value (SUVmean), maximum SUV (SUVmax), PSMA+ tumor volume, and tumor load (PSMA+ tumor volume × SUVmean). Parameters were extracted from the whole body and 4 regions. Association between PET parameters and radiographic progression-free survival (rPFS; primary objective), overall survival (OS), objective response rate (ORR), and prostate–specific antigen 50 (PSA50) response was assessed. Results: Most pts (92.7%) had PSMA uptake in bone. In both the whole-body and regional analyses, statistically significant associations of PSMA PET parameters to clinical outcomes were observed (whole-body data shown in Table). Higher whole-body SUVmean was associated with improved clinical outcomes; pts in the highest quartile (SUVmean: rPFS, ≥ 10.2; OS, ≥ 9.9) had a median rPFS and OS of 14.1 and 21.4 months, vs 5.8 and 14.5 months for those in the lowest quartile (< 6.0; < 5.7), respectively. Absence of PSMA+ lesions in bone, liver, and lymph node, and lower PSMA+ tumor load, were indicators of good prognosis. Conclusions: Higher SUVmean is strongly associated with improved outcomes with 177Lu-PSMA-617; clinical efficacy for different SUV levels vs the SoC arm is being assessed. Data support use of 68Ga-PSMA-11 PET/CT scan to identify pts who will benefit from PSMA-targeted radioligand therapy.[Table: see text]

Prognostic role of 11C-choline PET/CT scan in patients with metastatic castrate resistant prostate cancer undergoing primary docetaxel chemotherapy

BACKGROUND

We sought to assess the prognostic utility of 11C-choline positron emission tomography/computed tomography (PET/CT) in patients with metastatic castrate resistant prostate cancer (mCRPC) undergoing primary docetaxel chemotherapy.

METHODS

We performed a single institution retrospective analysis of 77 mCRPC patients who were treated with 6 cycles of docetaxel chemotherapy, and who also underwent 11C-choline PET/CT scans at baseline (before chemotherapy), mid-course (after 3 cycles), and posttherapy (after 6 cycles). We evaluated treatment response based on percent change in blood pool-corrected maximum standardized uptake value (SUVmax) of the target lesion on PET/CT, as well as percent change in serum prostate specific antigen (PSA). Logistic regression analysis was used to identify factors associated with complete treatment response. Progression free survival (PFS) analysis was performed using log-rank test and shown on Kaplan-Meier plot.

RESULTS

Percent change in blood pool-corrected SUVmax on mid-course scan was a significant predictor of complete response (odds ratio [OR]: 0.98, 95% confidence interval [CI]: 0.96-0.99, p = .0003), whereas percent change in PSA was not (OR: 0.99, 95% CI: 0.99-1.01, p = .6025). 57 of 77 patients (74%) achieved ≥20% reduction in blood pool-corrected SUVmax on mid-course; these patients were 3.6 times more likely to achieve complete response after full 6 cycles of docetaxel chemotherapy, compared to patients with <20% reduction in blood pool-corrected SUVmax (OR: 3.56, 95% CI: 1.04-16.52, p = .0420). Median PFS in the complete response group was 35.1 months (95% CI: 26.0-52.7 months), compared to 9.4 months (95% CI: 6.9-13.0 months) in the incomplete response group (p = .0005).

CONCLUSIONS

Our study showed that mid-course and posttherapy 11C-choline PET/CT evaluation for mCRPC patients undergoing primary docetaxel chemotherapy can predict full course treatment response and PFS, respectively. 11C-choline PET/CT imaging may provide valuable prognostic information to guide treatment choices for patients with mCRPC.

Rituximab for the Treatment of Refractory Cardiac Sarcoidosis-A Single Center Experience

OBJECTIVE

To examine the effect of anti-B cell therapy (rituximab) on cardiac inflammation and function in corticosteroid-refractory cardiac sarcoidosis.

BACKGROUND

Cardiac sarcoidosis (CS) is a rare cause of cardiomyopathy characterized by granulomatous inflammation involving the myocardium. While typically responsive to corticosteroid treatment, there is a critical need for identifying effective steroid-sparing agents for disease control. Despite growing evidence on the role of B-cells in the pathogenesis of sarcoidosis, there is limited data on the efficacy of anti-B cell therapy, specifically rituximab, for controlling CS.

METHODS

We reviewed the clinical experience at a tertiary care referral center of all patients with CS who received rituximab after failing to improve with initial immunosuppression therapy, which included corticosteroids. Fluorodeoxyglucose positron emission tomography (FDG-PET/CT) images before and after rituximab treatment were evaluated. All images were interpreted by 2 experienced nuclear medicine trained physicians.

RESULTS

We identified seven patients, (5 men, 2 women; mean age at diagnosis, 49.0±7.9 years) with active cardiac sarcoidosis who were treated with rituximab. The median length of follow-up was 5.1 years. All individuals, but 1, had received prior steroid-sparing agents in addition to corticosteroids. Rituximab was administered either as 1000 mg IV x 1 or x 2 doses, separated by 2 weeks. Repeat dosing, if appropriate, was considered after 6 months. All tolerated the infusions well.Inflammation as assessed by maximum SUV on cardiac FDG PET/CT uptake significantly decreased in 6 of 7 patients (median 6.0 to 4.5, Wilcoxon signed rank z: -1.8593, W: 3), whereas left ventricular ejection fraction improved or stabilized in 4 patients but decreased in 3. Mean left ventricular ejection fraction (LVEF) was 40.1% and 43.3% before and after treatment respectively (p=0.28). Three patients reported improved physical capacity, and 5 patients showed improved arrhythmic burden on Holter monitoring or ICD interrogation. One patient subsequently developed fungal catheter-associated infection and sepsis requiring discontinuation.

CONCLUSIONS

Rituximab was well tolerated and appeared to decrease inflammation, as assessed by cardiac FDG PET/CT scan, in all but 1 patient with active CS. These data suggest that rituximab may be a promising therapeutic option for CS, which deserves further study.

Treatment outcomes of well-differentiated high-grade (G3) neuroendocrine tumors

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Background: Recent WHO classification of NET has defined high-grade well-differentiated NET (NET G3) as a distinct entity that is clinically different from neuroendocrine carcinoma. The optimal treatment for NET G3 has not been well-described. This study aims to evaluate NET G3 response to different treatment regimens. Methods: This is a retrospective study of NET G3 patients within the Mayo Clinic database (Arizona, Florida, and Minnesota). Patient demographics along with treatment responses and survival were assessed. Primary end points were progression-free survival (PFS) and objective response rate (ORR) by RECIST 1.1 criteria. Results: 71 patients with NET G3 were identified. Systemic treatment data was available in 30 patients who had a median age of 59.5 years at time of diagnosis. The primary tumor was most commonly pancreatic (73.3%). Ki 67 index was ≥55% in 26.7% of cases. 56.7% of cases had > 1 metastatic site. Treatment regimens included: capecitabine+temozolomide (CAPTEM) (n = 20), somatostatin analog (SSA) (n = 14), carboplatin/cisplatin+etoposide (EP) (n = 7), everolimus (n = 2), FOLFOX (n = 7), and lutetium Lu 177 DOTATATE (PRRT) (n = 10). CAPTEM was the most commonly used regimen (10 first-line, and 10 second-line) with ORR of 35%, disease control rate (DCR) of 65%, and median PFS of 9.4 months. The table summarizes the treatment data and responses rates for the various therapies used. Conclusions: Among NET G3 patients treated at Mayo Clinic, CAPTEM was found to be the most commonly used treatment with reasonable efficacy and disease control. Other treatment options include SSA, PRRT, FOLFOX, and EP. Prospective studies evaluating different treatments effects in NET G3 patients are needed to determine an optimal treatment strategy. [Table: see text]

The impact of genetic mutations on response to radium-223 treatment for castration-resistant prostate cancer with bone metastases

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Background: Radium (Ra)-223 has become the cornerstone treatment in patients with metastatic castrate-resistant prostate cancer (mCRPC) with bone metastases. Ra-223 has been shown to suppress abnormal bone formation by inducing DNA double-strand breaks in tumor cells. This can reduce skeletal-related events, as well as improve survival and quality of life. Studies have indicated mutations that regulate DNA damage response in prostate cancer as susceptible to PARP inhibitors and platinum-based therapies. This study aims to evaluate mCRPC response to Ra-223 stratified by tumor genomics. Methods: This is a retrospective study of mCRPC patients who received Ra-223 and genetic testing within the Mayo Clinic database (Arizona, Florida, and Minnesota). Patient demographics, genetic mutations, treatment responses in terms of alkaline phosphatase (ALP) and prostate-specific antigen (PSA), and survival were assessed. Primary end points were progression-free survival (PFS) and overall survival (OS) from time of first radium treatment. Results: 239 mCRPC patients treated with Ra-223 were identified. Germline and/or somatic genetic sequencing was available in 50 patients, who had a median age of 61 years at time of diagnosis and 68 years at time of Ra-223 treatment. Median Gleason score at time of diagnosis was 8.0. 100% of patients received prior androgen deprivation therapy. 72% received prior docetaxel, and 18% received prior cabazitaxel. Notable mutations included TP53 (45.2%), TMPRSS2-ERG (28.6%), PTEN (26.2%), BRCA1/2 (14.3%), ATM (9.3%), CDK12 (7.1%), and Rb (4.9%). TMPRSS2-ERG was the second most commonly found mutation, with median OS 12.7 mo versus 15.4 mo in patients without TMPRSS2-ERG mutations (p = 0.099). In patients with CDK12 mutations (2 of 28 tested positive), PFS was 10.4 mo versus 5.6 mo in patients without CDK12 mutations (p = 0.157). The assessment of ALP and PSA response to radium treatment stratified by genetic mutation did not reach statistical significance. Conclusions: Among mCRPC patients treated with Ra-223 at Mayo Clinic, TMPRSS2-ERG was the second most commonly found genetic mutation and had observed worse survival outcomes that approached statistical significance. Prospective studies and increased sample sizes are needed to determine the impact of genetic mutations in response to Ra-223.

Radiographic paradoxical response in patients with metastatic castrate-resistant prostate cancer (mCRPC) undergoing treatment with second-generation hormone therapy (second-HT)

5577

Background: Prostate specific antigen (PSA) has well-recognized limitations as a marker for treatment response and disease progression. A post hoc analysis of the PREVAIL trial reported 24.5% of chemotherapy naïve mCRPC patients on enzalutamide had radiographic progression on conventional imaging with non-rising PSA. In this study, we sought to retrospectively compare PSA levels with C-11 choline positron emission tomography/ computed tomography (PET/CT) images in patients with m-CRPC on 2nd-HT with prior use of chemotherapy. Methods: We identified 123 patients with mCRPC on 2nd-HT following prior use of docetaxel chemotherapy (Abiraterone, n = 106; Enzalutamide, n = 17). Patients underwent serial PSA testing and C-11 choline PET/ CTs every 3–6 months. Disease progression was defined by the increase in blood pool corrected maximum standardized uptake value (SUVmax) of the index lesion on C-11 choline PET/CT scan. Suspicious lesions were confirmed by biopsy and/or conventional imaging. Results: Approximately 43% (n = 53) of patients had radiographic disease progression while on 2nd-HT. At time of radiographic progression, 60.4% of patients showed a parallel rise in PSA (Group-A), while 39.6% showed a paradoxical response; defined as radiographic progression with stable or down-trending PSA (Group-B). Median PSA at time of progression was 3.1 ng/ml for Group-A, and 1.3 ng/ml for Group-B (p-value = 0.0176). Median SUVmax was the same (4.9 Group-A, 4.6 Group-B; p-value = 0.6072). Bone-predominance progression was more significant in Group-B (90%) versus Group-A (65%) (p-value = 0.0309). The median time for radiographic progression was 9.5 months versus 3.9 months for Group-A and Group-B, respectively (Log-Rank = 0.0063). Conclusions: Metabolic imaging is a useful tool that should complement PSA in the evaluation of treatment response and disease progression in mCRPC patients on 2nd-HT, especially considering the paradoxical response observed in our data.

Role of metastases-directed therapy (MDT) in the management of solitary metastatic prostate cancer

143

Background: Systemic treatment in the management of metastatic prostate cancer is inevitable. However, there is a growing interest in metastases-directed therapy (MDT). We sought to investigate the efficacy of MDT in treating patients with solitary metastatic prostate cancer and hence, delaying initiation of systemic treatment (i.e., Androgen deprivation therapy or chemotherapy). Methods: We retrospectively identified 61 patients treated with targeted therapy in the form of surgery (n = 30), stereotactic body radiation therapy (SBRT) (n = 25), or cryotherapy (n = 7) for their solitary metastases prostate cancer. Complete response was defined by achieving a PSA value of ≤0.2 ng/ml plus resolution of the solitary metastatic lesion on C-11 choline PET choline scan, while incomplete response was defined by a residual PSA of > 0.2 ng/ml and/or radiographic evidence of disease following metastases-targeted therapy. Results: Mean (±SD) age was 68.4 (±7.8) yrs., median (IQR) primary Gleason Score was 7 (7-9) and median (IQR) pre-MDT PSA was 2 (1.3-3.8) ng/ml. Median (IQR) time from primary treatment of the prostate to MDT was 5.1 (2.7-10.1) years. None of the patients were on hormone therapy at the time of presentation with solitary metastases prostate cancer. 30 patients had bone metastases, 29 patients had lymph node metastases, 1 patient had soft tissue metastasis (pelvic metastatic mass), and another patient had visceral metastasis (to the lung). 42% of the patients (n = 26) achieved complete response to targeted therapy. Median time to initiation of 2nd line systemic treatment following MDT was 17.8 months for the complete responders versus 9.3 months for incomplete responders. 11% of the patients (n = 7) did not require 2nd line therapy after their MDT for a mean (±SD) time of 56.9 (±22.5) months. Conclusions: The use of targeted therapy in the management of patients with solitary metastatic disease or low-volume metastatic disease can provide comparable outcomes to those of systemic treatment. Further studies are warranted.

Non-rising PSA disease progression on C-11 choline PET/CT imaging in patients receiving second generation hormone therapies (2nd-HT)

144

Background: Despite having well-recognized limitations, urologists often rely on serial PSA testing as a marker for treatment response or disease progression. To determine if PSA was indeed a reliable marker for treatment response or disease progression, we compared PSA levels against C-11 choline PET/CT in the evaluation of patients with advanced prostate cancer treated with second generation hormonal therapy (2nd-HT). Methods: We retrospectively identified 239 patients who were undergoing treatment with 2nd-HT (enzalutamide or abiraterone) for advanced prostate cancer. While on treatment, patients underwent serial PSA testing and C-11 choline PET/ CTs every 3 – 6 months. Paradoxical response was defined as increasing blood pool-corrected SUVmax of known choline-avid lesions and/or identification of new choline-avid lesions, despite stable or down-trending PSA. Results: Median (IQR) age was 70.4(64.3 – 75.7) years and median (IQR) primary Gleason Score was 8 (7 – 9). In our study, 19% of patients (n = 46/239) who were receiving 2nd-HT exhibited paradoxical response. Median (IQR) PSA and corrected SUVmax at baseline evaluation were 1.3 ng/mL (0.3 – 12.8 ng/mL) and 3.5 (1.8 – 5.8), respectively. Median (IQR) PSA and corrected SUVmax at the time of paradoxical response were 0.4 ng/mL (0.1 – 5.4 ng/mL) and 4.5 (2.8 – 6.8), respectively. The median duration of 2nd-HT treatment prior to detection of paradoxical response was 4.8 months (2.9 – 10.1 months). No significant difference was noted between patients receiving enzalutamide versus abiraterone (p = 0.35). Independent predictors of paradoxical response were prior primary systemic treatment (i.e. hormonal/chemo-hormonal therapy versus local therapy) and patient’s age at time of 2nd-HT initiation on univariate and multivariate analysis. Conclusions: Our retrospective review demonstrated prostate cancer disease progression discordant with PSA down-trending in 19% of patients receiving 2nd-HT. We conclude that in this subset of patients with advanced prostate cancer, PSA may not be a reliable marker of treatment response of disease progression, and routine radiographic evaluation in these patients is warranted.

Efficacy of somatostatin analog (SSA) monotherapy for well-differentiated grade 3 (G3) gastroenteropancreatic neuroendocrine tumors (NETs)

617

Background: Currently, there is no published data on the efficacy of SSAs for well-differentiated G3 NETs. Randomized trials have demonstrated a progression-free survival (PFS) benefit and limited tumor response for lower grade 1-2 NETs, but the optimal systemic therapy for metastatic/unresectable G3 NETs is unknown. We sought to evaluate the efficacy of SSAs in G3 NETs. Methods: We performed a retrospective analysis of Mayo Clinic patients treated with SSAs for metastatic/unresectable G3 NETs, querying data from 1992 - present. Inclusion criteria were: centrally reviewed pathology confirming well-differentiated morphology, G3 based on WHO classification, SSA monotherapy, and radiological data available to assess response. Patients who had prior lines of treatment were included as long they subsequently were treated with single-agent SSA. Poorly-differentiated tumors were excluded. The primary endpoint was PFS. Best overall response was determined by radiographic regression, stabilization, or progression of tumor size. Results: Ninety patient records were reviewed, with 14 meeting inclusion criteria (diagnosed 2014 – 2018). Median Ki-67 proliferative index was 25%. Two patients (14%) had a partial response to SSA therapy, five (36%) had stable disease, and seven (50%) had progressive disease. The estimated median PFS was 4.4 months (95% CI 2.9 – 24). Of the 7 patients with stable disease or partial response, the median time to progression was 8.7 months. Three patients had stable disease for greater than 9 months (24, 29 and 42 months, respectively). Overall survival was not estimable. There was no association of Ki-67 index with PFS based on a proportional hazards model. Conclusions: This is the first report on the efficacy of SSAs for G3 NETs. Although half of the patients in our series had at least stable disease, the PFS was modest at only 4.4 months. Given their favorable side-effect profile compared to cytotoxic chemotherapy, SSAs may present an attractive option to be further explored in a prospective fashion. We are presently updating this data by reassessing response using RECIST criteria.

PET/CT in an 8-Year-Old Girl With Epstein-Barr Virus-Associated Smooth Muscle Tumor

Epstein-Barr virus-associated smooth muscle tumor is a rare indolent neoplasm, which can occur in unusual locations. It has been reported in immunosuppressed individuals in only 3 settings: posttransplant, human immunodeficiency virus infection, and primary immunodeficiency. Here, we present CT, MRI, and F-FDG PET/CT findings of Epstein-Barr virus-associated smooth muscle tumor in an 8-year-old girl with primary immunodeficiency and metachronous adrenal involvement.

Bone Scan in Evaluation of Bone Viability in Severe Frostbite of the Hand

A 39-year-old male presented to the emergency department (ED) with frostbite to the fingers of both hands. In the ED, he received warm baths, acetylsalicylic acid, clopidogrel, and heparin. A three-phase bone scintigraphy with technetium-99m-methylene diphosphonate revealed absent radiotracer uptake in distal phalanges of both hands. The patient received acetylsalicylic acid, clopidogrel and wound care for the next 5 days and made an excellent recovery with satisfactory wound healing in both hands. Early rapid rewarming and reperfusion can improve the prognosis significantly and therefore bone scan done within first 1–2 days may give spurious results.

Nested Stromal-epithelial Tumor of Liver with Recurrent Extrahepatic Metastasis: Role of Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography

Nested stromal-epithelial tumor (NSET) is a very rare nonhepatocytic and nonbiliary primary tumor of the liver. An 8-year-old boy was incidentally detected with hepatic lesions, involving both lobes of the liver for which he later underwent orthotopic liver transplant. The hepatic lesions were confirmed to be NSET following histopathological examination of explant liver specimen. He later developed recurrence with multiple metastatic lesions, including multi-station nodal and right talar bone involvement. We here present the case highlighting the importance of ¹⁸F-fludeoxyglucose positron emission tomography/computed tomography in the management of this rare tumor, in particular for monitoring disease progression and/or recurrence.

A case of granulomatous slack skin cutaneous T-cell lymphoma: PET/CT imaging findings

A 24-year-old female presented with granulomatous slack skin (GSS) cutaneous T-cell lymphoma. The patient underwent systemic chemotherapy. Owing to the development of several chemotherapy-related complications, therapy was discontinued. Subsequently, disease progression was noted clinically. Our patient’s disease progression was clearly demonstrated by 18F-fludeoxyglucose positron emission tomography (PET)/CT findings. PET/CT imaging findings of GSS have not yet previously been reported. In this report, we present PET/CT characteristics of a patient with GSS.