Citations

Abstract Disclosure: P. Hopmann: None. S. Lund: None. T. Foster: None. B. Dy: None. T. McKenzie: None. G. Johnson: None. R.A. Wermers: None. M. Lyden: None. Background: Previous studies have demonstrated that C11 choline positron emission tomography/computed tomography (Choline-PET/CT) can localize abnormal parathyroid glands in the re-operative setting. This study assesses a large volume of patients with primary hyperparathyroidism (1HPT) who underwent Choline-PET/CT to confirm its utility in the setting of negative or equivocal conventional imaging. Methods: All patients who underwent Choline-PET/CT for evaluation of 1HPT from July 2017 to July 2024 at a single institution were reviewed. Inclusion criteria were patients who underwent parathyroidectomy and had lab testing to assess for cure (defined as >50% drop from baseline PTH and into normal range, or resolution of hypercalcemia at follow-up). Sensitivity, positive predictive value (PPV), false negative rate (FNR), and accuracy were compared to conventional imaging (neck ultrasound, parathyroid scan, and parathyroid four-dimensional CT (4D-CT)). Subgroup analysis was conducted comparing sensitivity of modalities among index operations, and separately in re-operations. Results: 176 patients were identified. 85 underwent parathyroidectomy, 1 patient was excluded due to lacking data to evaluate for cure. Of 91 patients who did not undergo parathyroidectomy, 45 were non-localizing on all imaging, and 46 had positive Choline-PET/CT findings but opted against surgery due to mild disease or prohibitive re-operative risk. Of the included 84 parathyroidectomy patients, 61 failed to localize on at least one conventional modality, and 15 failed to localize on all conventional studies. 67 patients (80%) achieved cure, of whom 53 were re-operations (range of 1-4 prior operations, average 1.5). Choline-PET/CT outperformed conventional modalities across sensitivity, PPV, FNR, and accuracy. Among index operations, Choline-PET/CT had significantly higher sensitivity than conventional modalities (100% vs 27% for ultrasound, 30% for parathyroid scan, 29% for 4D-CT; p values ≤0.01). This was also true in re-operations (95% for Choline-PET/CT vs 13% for ultrasound, 30% for parathyroid scan, 32% for 4D-CT; p values <0.01). Conclusion: C11 choline-PET/CT is a valuable imaging modality in the re-operative setting and demonstrates utility for index operations. It provides localization when other modalities fail and allows for a high surgical cure rate. Further investigation into its utility as a primary imaging modality is warranted. Presentation: Monday, July 14, 2025

TPS5125 Background: Prostate cancer (PC) is common and despite recent advances in treatment options, patients with metastatic disease still have poor outcomes. The double PSMA binding moiety of SAR-bisPSMA in 64 Cu-SAR-bisPSMA (imaging) and 67 Cu-SAR-bisPSMA (therapy) may offer advantages compared to currently used single-target PSMA agents. Clinical evidence demonstrated 2-3 times higher uptake of 64 Cu-SAR-bisPSMA compared to the single-target PSMA agent, 68 Ga-PSMA-11. Pre-clinical efficacy data of 67 Cu-SAR-bisPSMA in mice showed statistically significant tumor growth inhibition and increased survival in a PC xenograft study. These results led to the development of the SECuRE trial, which aims to assess the safety and anti-tumor efficacy of 67 Cu-SAR-bisPSMA in patients with metastatic castrate resistant PC (mCRPC). Methods: SECuRE is a Phase I/IIa multi-center, open-label, non-randomized, dose-escalation and cohort expansion study of 64 Cu-SAR-bisPSMA and 67 Cu-SAR-bisPSMA in patients with mCRPC. The target population is patients who have progressed despite having at least one androgen receptor pathway inhibitor and demonstrate positivity on 64 Cu-SAR-bisPSMA PET. The study comprises 3 phases: Dosimetry (N=6), Dose Escalation (N~24) and Cohort Expansion (N=24). The 67 Cu-SAR-bisPSMA dose levels investigated in the Dose Escalation Phase are: 4 GBq (cohort 1, single dose), 8 GBq (cohort 2, single dose), 12 GBq (cohort 3, single dose) and 24 GBq across two doses (cohort 4, two doses at the maximum tolerated dose or maximum feasible dose [MTD/MFD] established in cohorts 1-3; two additional doses may be offered in case of radiological non-progression). In the Cohort Expansion phase, participants will receive 2 doses of 67 Cu-SAR-bisPSMA at the recommended dose determined in the Dose Escalation Phase (those with radiological non-progression may be offered up to 2 additional doses). A recent protocol amendment increased the number of participants from 14 to 24 in the Cohort Expansion phase, in which 8 will receive combination therapy of 67 Cu-SAR-bisPSMA with enzalutamide. The primary and key secondary objectives include assessment of 64 Cu- and 67 Cu-SAR-bisPSMA’s safety and dosimetry and determining the anti-tumor efficacy of 67 Cu-SAR-bisPSMA. Response to 67 Cu-SAR-bisPSMA will be assessed biochemically (≥50% decline in prostate-specific antigen) and radiographically (by RECIST V1.1 and PCWG3). Clinical trial information: NCT04868604 .

e15046 Background: BRAF V600 is the most common driver mutation in melanoma, seen in ≈50% of patients. Recently, the use of liquid biopsy assays that are based on circulating tumor DNA (ctDNA) has become widespread for diagnosis and residual disease monitoring. We have previously reported on our droplet digital PCR (ddPCR) test as a liquid biopsy for BRAF mutant (BRAFm) melanoma. Here we report the correlation between clinical and radiological parameters and ddPCR test results. Methods: Using the department of laboratory medicine archives, we have identified all biopsy proven BRAFm melanoma patients that were tested with the BRAF V600 ddPCR assay at our institution over the years 2018-2024. All patients had blood samples collected, and cell free DNA (cfDNA) was extracted from plasma using the Qiagen QIAamp Circulating Nucleic Acid Kit. cfDNA was evaluated with a BioRad QX200 droplet digital PCR platform assessing for BRAF V600E/K mutations. Clinical and demographic data were collected from medical records. Radiometabolic features including volumetric data and FDG PET SUV values were collected and analyzed using the MIM software (MIM Software Inc., Beachwood, OH, USA). Univariate and multivariate analyses were used to assess correlations between baseline variables and test results. Results: 71 patients were identified. The median age was 59 (26-85), 54% were males. 46 patients (65%) had a positive test result which was based on a cut-off of ≥4 mutant copies per ml. 65 patients (92%) had active disease on imaging studies, of which those with a positive test result were younger (p = 0.047), had a higher proportion of osseous metastases (p = 0.02) and had a higher number of lesions (p = 0.006). There was no difference in the median overall survival between the groups (11 months vs. 33 months for positive and negative result respectively, log-rank test; p = 0.15). Total tumor volume on PET-CT (in ml) was predictive of the quantitative ddPCR test result (in copies per ml), with every increase in 10 ml of tumor leading to an expected increase of 370 copies per ml (p < 0.001). Multivariate models have failed to show a correlation between baseline parameters and the quantitative ddPCR test result. When performing the analyses using logistic regression models with the binary ddPCR test result as the outcome, osseous metastases were predictive in a univariate model (OR = 4.3, 95% CI 1.4-15.4). The best fit multivariate model showed that higher burden of disease with ≥6 lesions (OR = 6.57, 95% CI 1.24-44.3) and elevated LDH (OR = 8.8, 95% CI 1.83-56.91) were associated with an increased risk for a positive result, while younger age was associated with decreased risk for a positive result (OR = 0.92, 95% CI 0.86-0.97). Conclusions: The results of ddPCR testing for BRAF mutation are correlated with the radiological and volumetric extent of the disease. This test could be useful in patients presenting with high-burden disease when a fast turnaround time is needed.

Abstract Background: Fibroblast activation protein (FAP) is a type II integral membrane glycoprotein, highly expressed on the cell surface of cancer-associated fibroblasts (CAFs) present in the tumor microenvironment of most epithelial cancers and showing limited expression in normal tissues. Given this expression profile, FAP appears to be a promising target for radioligand therapy that has pan-cancer potential. [177Lu]Lu-NNS309 is a FAP-targeted radiopharmaceutical that shows improved tumor retention and demonstrates promising anti-tumor activity in translationally relevant preclinical models (e.g., PDAC, NSCLC) where FAP is expressed on CAFs. Methods: CFXX489A12101 (NCT06562192) is a first-in-human phase I, open-label, multi-center study of [177Lu]Lu-NNS309 in patients with pancreatic ductal adenocarcinoma (PDAC), non-small cell lung cancer (NSCLC), breast cancer (BC), and colorectal cancer (CRC). The study includes a dose escalation part followed by a dose expansion part. Key eligibility criteria include prior treatment for locally advanced unresectable or metastatic disease and having all measurable lesions (per RECIST 1.1) showing [68Ga]Ga-NNS309 uptake on positron emission tomography/computed tomography (PET/CT). Patients who are eligible for treatment receive one dose of [177Lu]Lu-NNS309 on day 1 of each cycle. A 6-week and a 4-week dosing schedule will be explored. Dosimetry data will be obtained from patients in the dose escalation part after the first dose and will be used to calculate the cumulative radiation exposure. Dose escalation will be guided by a Bayesian hierarchical logistic regression model with overdose control (EWOC) principle, and assessment of all relevant data available from all dose levels including safety, tolerability, clinical dosimetry, pharmacodynamics, and preliminary efficacy. Once the recommended dose(s) (RD) and schedule(s) of [177Lu]Lu-NNS309 are determined, the expansion part may open and will include patients with locally advanced or metastatic PDAC (n∼20), locally advanced or metastatic NSCLC (n∼20), HR+/HER2- ductal BC (n∼15), HR+/HER2- lobular BC (n∼15), and triple negative BC (; n∼24).The primary objectives of the study are to evaluate the safety and tolerability of [177Lu]Lu-NNS309 and to identify the RD(s) and regimen(s) of [177Lu]Lu-NNS309 for further clinical evaluation. Secondary objectives of the study are to evaluate the preliminary anti-tumor activity of [177Lu]Lu-NNS309, characterize the pharmacokinetics of [177Lu]Lu-NNS309 in blood and urine, the radiation dosimetry for organs and tumor lesions, and to evaluate the safety and imaging properties of [68Ga]Ga-NNS309. Conclusion: The study is currently enrolling in the dose escalation part. Citation Format: Ravit Geva, Daniel Juneau, Shadi Abdar Esfahani, Cristiano Ferrario, Farshad Moradi, Amir Iravani, Jordi Ahnert, Ivan Manuel Victoria Ruiz, Thibaud Koessler, Aitana Calvo Ferrandiz, Bernard Doger de Speville, Patrick Flamen, Albiruni Razak, Desiree Deandreis, Laure Al-Mansour, Niklaus Schaefer, James Nagarajah, Hilde Nienhuis, Marco Maccauro, Angelina Filice, Jonathan Goldman, Ken Herrmann, Matthias Eiber, Alexander Drzezga, Martin Heuschkel, Jonathan McConathy, Johnson Geoffrey, Ephraim Parent, Yasutoshi Kuboki, Shizuka Origuchi, Xuan Mai Couillebault, Elisa Garcia Garayoa, Jayarama Naidu Roopa, Christopher Straub, Dominik Hainzl, Xinyu Chen, Fang Yang, Eirini Pectasides, Brandon Mancini. Phase I open-label, multi-center study to evaluate the safety, tolerability, dosimetry, and preliminary activity of FXX489 ([177Lu]Lu-NNS309) in patients with pancreatic, lung, breast and colorectal cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr CT112.

114 Background: Oncologists have traditionally relied upon serial assessments of PSA and periodic imaging (i.e., every 2 to 3 cycles) to monitor treatment response. Early identification of disease progression allows for faster transitions to alternative therapies that might be more effective. In this study, we evaluated the utility of post-treatment SPECT/CT for earlier detection of treatment failure in patients receiving Lutetium-177–PSMA-617 (LuPSMA). Methods: We queried an IRB-approved registry including all patients starting LuPSMA at Mayo Clinic, MN, in the interval of March 2022 to March 2023. Those receiving fewer than 2 cycles of treatment and missing SPECT/CT data were excluded. We reviewed clinical notes to document the date and reason(s) for treatment discontinuation. The assembled cohort consists of patients stopping LuPSMA for progressive disease ([PD], categorized as biochemical, radiographic, or both). Results of the prior SPECT/CT imaging reports were reviewed. At our institution SPECT/CT images are typically acquired on the day after each infusion. Metrics collected from the radiology reports included: new foci of PSMA localization since the prior PSMA PET or SPECT/CT, suspicion for new non-PSMA avid disease, and a visual determination of PSMA-avid tumor volume. Results: A total of 256 patients received an initial cycle of LuPSMA. SPECT/CT imaging data for at least 2 consecutive treatment cycles was available for 68 patients who developed PD after a median (IQR) of 3 (2-4) cycles. There were 55 patients (81%) with both biochemical and radiographic evidence of PD, 7 (10%) with biochemical only progression, and 6 (9%) with radiographic only progression. The most used imaging modality for response assessment was PSMA PET/CT (n=46, 67%), followed by conventional imaging (n=9, 13%), and choline PET/CT (n=5, 7%). The median time between most recent post-therapy SPECT/CT and determination of PD was 39 days. The prior SPECT/CT had detected new foci of PSMA avid disease in 12 (18%) cases and new non-PSMA avid disease in 5 (7%) cases. Two patients had both new PSMA-avid and non-PSMA avid lesions. The most common sites of new PSMA-avid disease on SPECT/CT were bone (n=10) and liver (n=2). A total of 20 (29%) patients had visually increased tumor volume on SPECT/CT, 9 (45%) of which had no new lesions. In total, 24 of 68 patients (35%) had early detection of treatment futility detected by SPECT/CT. At a median (IQR) follow-up time of 8 (6.4-12) mo, the median OS [95% CI] was similar for patients with PD detected on SPECT/CT (7.8 [6.6 – 9] mo) compared to those without clear evidence of PD on SPECT/CT(8.4 [6.4-10.3] mo, p=0.885). Conclusions: Post-treatment SPECT/CT imaging may complement traditional forms of response assessment and provide an earlier warning of treatment failure through identification of new PSMA-avid lesions, non-PSMA avid disease, and increased tumor volume.

112 Background: We now have more than a decade of experience using Androgen Receptor Pathway Inhibitors (ARPIs) across various disease states of prostate cancer, and the safety of their combination with Lutetium-177–PSMA-617 has been demonstrated in VISION and other large randomized clinical trials. However, real-world data on treatment patterns and outcomes involving combination therapies with 177 Lu-PSMA-617 remain limited. Methods: For this analysis, we utilized the Mayo Clinic Rochester radiopharmaceutical database, a prospectively maintained retrospective database containing all patients who received 177 Lu-PSMA-617 at our institution. We focused on patients who started treatment from March 2022 to March 2023. Patients receiving an ARPI (abiraterone acetate, enzalutamide, apalutamide, or darolutamide) during the course of 177 Lu-PSMA-617 treatment were identified, inclusive of patients who continued using an ARPI prescribed as a prior line of treatment and those who started (i.e., switched) to a new ARPI. Baseline clinicopathologic and imaging characteristics were abstracted and compared using the Mann-Whitney U and Chi-square tests. Best PSA response during treatment was reported as a percent decline from baseline. Survival was calculated from the date of the first cycle of 177 Lu-PSMA-617. PSA50 response and overall survival (OS) outcomes for the two groups (concurrent use of ARPI vs. 177 Lu-PSMA-617 alone) were compared using the Chi-square test and Kaplan-Meier method, respectively. A multivariate Cox regression analysis was performed, including established prognostic factors. Results: An ARPI was prescribed to 106 of the 256 patients (41.4%) starting 177 Lu-PSMA-617 in the interval of March 2022 to March 2023. With regards to baseline characteristics, those receiving an ARPI concurrently with 177 Lu-PSMA-617 had a lower PSA (3.4 vs 29.7 ng/mL, p < 0.001) and a lower frequency of bone (77.4% vs. 87.4%, p = 0.035) and visceral metastases (18.9 vs 34%, p = 0.008) at start of treatment. Median follow-up for the overall cohort (IQR) was 19.1 months (8.7 – 23.6). Patients receiving an ARPI plus 177 Lu-PSMA-617, as compared to 177 Lu-PSMA-617 alone, were more likely to complete all 6 planned doses of treatment (63.2% vs. 48.7%, p < 0.001), though the PSA50 response rate was similar (49.1% vs 47.3%, p = 0.786). Median OS [95% CI] for the overall cohort was 21.3 [16.7 – 25.9] months and significantly longer for those receiving ARPI with 177 Lu-PSMA-617 (NR [NE – NE]) as compared to 177 Lu-PSMA-617 alone (15.3 mo [11.6 – 19.1], p < 0.001). However, on multivariate analysis including known prognostic variables, use of ARPI was not independently associated with improved survival (HR = 1.03 [CI: 0.68 to 1.55], p = 0.891). Conclusions: Patients receiving an ARPI with 177 Lu-PSMA-617 were more likely to complete all 6 cycles of treatment, but no clear differences in survival were observed on multivariate analysis.

129 Background: Few studies have explored the use of focal therapies to address select sites of resistant disease in men receiving 177-Lu-PSMA-617 for metastatic castrate resistant prostate cancer (mCRPC). Our institutional practice is to offer SBRT for patients with up to 5 sites of oligoprogression or non-responding lesions while undergoing 177Lu-PSMA-617 (every 6 weeks for 6 cycles total). This is determined by PSMA or choline PET imaging during the course of 177Lu-PSMA-617. Herein, we evaluated the safety of adding target SBRT during treatment with 177Lu-PSMA-617. Methods: This retrospective single institution analysis was conducted via systematic chart review to evaluate for adverse events during or after treatment. Grading of treatment-related adverse events was conducted using Common Terminology Criteria for Adverse Events Version 5.0 (CTCAE v5). Results: Thirty-one patients receiving 177Lu-PSMA-617 with 51 sites of oligoprogressive or non-responding metastatic disease were treated with SBRT. The median number of sites treated was 1 (range 1-4). Most patients received SBRT immediately after cycle 6 (32%) or after cycle 3 or 4 (42%). Bone was the most commonly treated site of disease (90%) with the majority (54%) of bone sites being spine or sacrum, followed by lymph nodes (10%). Ultimately, 84% of patients completed all 6 cycles of 177Lu-PSMA-617 (range 4-6). The median follow-up time was 19.1 months (IQR 15.5-22.4) after 177Lu-PSMA-617 therapy start. A total of 2 patients experienced a pathologic fracture within the SBRT treatment field that could possibly be related to radiotherapy. One patient experienced a grade 2 neuropathy which may have been related to radiation therapy. Other potential adverse events are listed (Table). Conclusions: Our data demonstrates a low rate of significant toxicity with the use SBRT during treatment with 177Lu-PSMA-617. Further study is indicated to determine the oncologic efficacy and potential late side effects of this treatment strategy. Adverse events. Event All Grades Grade > 3 Any Adverse Event 104 2 Anemia 29 (94%) 0 Low Platelets 11 (35.5%) 1 (3.2%) Any Pathologic Fracture 7 (22.5%) 1 (3.2%) Possible SBRT-related Pathologic Fracture 2 (6.5%) 1 (3.2%) Bone Pain Flare 3 (9.6%) 0 Neuropathy 1 (3.2%) 0

Objective To define the natural history, patterns of recurrence and treatment modalities for local prostate cancer (PCa) recurrence following radical prostatectomy (RP) and radiation therapy (RT), and to investigate factors that could predict metastasis‐free survival (MFS) in this unique patient population. Methods We queried a prospectively maintained PCa registry to identify men developing in‐field recurrence (IFR) following RP and RT from 2008 to 2021 at a single institution. IFR was defined as biopsy‐proven recurrent PCa or the presence of persistent positron emission tomography‐avid lesions in the prior radiation field without evidence of metastasis. Cox regression was conducted to determine predictors of MFS. Kaplan–Meier methods were used to calculate MFS, cancer‐specific survival (CSS) and overall survival (OS) for patients in three primary therapy categories: cryoablation, androgen deprivation therapy (ADT) alone, and surveillance. Results Of 4575 patients from our registry, 108 (2.3%) with IFR were identified. The median (interquartile range [IQR]) time to IFR from salvage treatment was 78 (50–126) months. A total of 29 patients (26%) were managed with cryoablation, 23 (21%) with ADT, and 28 (25%) with surveillance. The median (IQR) follow‐up was 76 (48–100) months. There were no statistically significant differences in MFS ( P = 0.67) or OS ( P = 0.07) among the three primary treatment cohorts. Patients treated with ADT or cryoablation had longer CSS compared to patients managed with surveillance ( P = 0.047). Conclusions We found that IFR may present years after completion of primary treatment for PCa. While curative management strategies may be attempted, local and distant metastatic recurrence is common and often requires systemic therapy.

Purpose: The purpose was to evaluate the pathological nature of focal thyroid uptake seen in 11C-Choline PET/CT performed for prostate cancer. Material and methods: The study was IRB-approved. All 11C-Choline PET/CT exam reports for studies performed between January 01, 2018, and July 30, 2021, in male patients with prostate cancer in our institution were retrospectively reviewed. Exams with “focal thyroid uptake” on their final report were selected. Patients with surgery or ablation in the thyroid prior to the PET/CT, proven parathyroid adenomas or absent thyroid ultrasound were excluded. Repeated PET/CT exams of same patient were excluded. PET images were analyzed visually and semi-quantitatively by measuring the maximum standardized uptake value (SUVmax) of the focal thyroid uptake. Available thyroid ultrasound images, cytology and pathology reports were reviewed. Statistical analyses were performed. Results: Out of 10,047 sequential 11C-Choline PET/CT studies, 318 reports included “focal thyroid uptake.” About 128 of these studies were repeat exams and were excluded. Additional 87 patients were excluded, because the uptake was determined to be adjacent, rather than confined to the thyroid gland. Out of the remaining 103 patients, 74 patients had focal thyroid uptake and concurrent thyroid sonographic evaluation. Out of the 74 focal uptakes evaluated with ultrasound, 21 were presumed benign thyroid nodules based on the ultrasound and 53 had further evaluation with biopsy. Sixty three nodules were benign (21 presumed benign on ultrasound and 42 cytology or surgical pathology-proven), 9 nodules were malignant and 2 remained indeterminate. There was no significant difference between the SUVs of the benign and malignant groups (P > .3). Conclusion: In this retrospective study of patients with prostate cancer who underwent 11C-Choline PET/CT, we identified a group of patients who underwent thyroid ultrasound for incidental finding of focal 11C-Choline thyroid uptake. Incidence of malignancy in this group was 12%. Therefore, further investigation with ultrasound and possibly ultrasound-guided biopsy may be warranted when a choline avid thyroid nodule is found incidentally on choline PET.

Abstract Rationale Fibrosing mediastinitis (FM) is an uncommon fibroinflammatory condition without established or effective medical therapies. Infiltrating B lymphocytes are commonly present, and progressive fibrosis compromises mediastinal structures, including blood vessels and airways, resulting in significant morbidity and mortality. Objective To evaluate the benefits and side effects of rituximab in patients with progressive and symptomatic FM. Methods We treated 22 patients (median age, 35 yr; range, 15–68 yr; 45% female) with metabolically active, progressive FM with rituximab on an off-label basis. Additionally, patients were administered pneumocystis and antifungal prophylaxis when immunosuppressed with rituximab. Modeling of longitudinal treatment response based on changes in relative lesion volume from baseline was performed retrospectively using functional data analysis, and time-to-event modeling was performed to estimate treatment response rates based on a &gt;30% reduction in pretreatment volume. The primary endpoints were lack of disease progression and change in mediastinal lesion volume on computed tomography (evaluated retrospectively). Results No patient experienced disease progression after rituximab therapy. Median clinical follow-up was 42 months (range, 7–94 mo) and imaging follow-up 21 months (range, 7–62 mo). A total of 82% of patients had confirmed histoplasmosis-associated FM. After rituximab treatment, a 49.6% (95% confidence interval, 17.5–64.4%) mean estimated decrease in pretreatment lesion volume was observed at 24 months. The estimated objective treatment response rate was 47.9% (95% confidence interval, 26.7–70.3%). Conclusions This observational study suggests that rituximab is a well tolerated and potentially effective therapy in a cohort of patients with symptomatic and progressive FM.