Areas Of Radiotracer Uptake Research Articles

Advancements and future directions in positron emission tomography-guided radiotherapy: a narrative review.

Positron emission tomography (PET) imaging has been useful in delineating tumor volumes and allowing for improved radiation treatment. The field of PET-guided radiotherapy is rapidly growing and will have significant impact on radiotherapy delivery in the future. This narrative review provides an overview of the current state of PET-guided radiotherapy as well as the future directions of the field. For this narrative review, PubMed was searched for articles from 2010-2023. A total of 18 keywords or phrases were searched to provide an overview of PET-guided radiotherapy, radiotracers, the role of PET-guided radiotherapy in oligometastatic disease, and biology-guided radiotherapy (BgRT). The first 300 results for each keyword were searched and relevant articles were extracted. The references of these articles were also reviewed for relevant articles. In radiotherapy, 18F-2-fluoro-2-deoxy-D-glucose (F-FDG or FDG) is the major radiotracer for PET and when combined with computed tomography (CT) scan allows for anatomic visualization of metabolically active malignancy. Novel radiotracers are being explored to delineate certain cell types and numerous tumor metrics including metabolism, hypoxia, vascularity, and cellular proliferation. This molecular and functional imaging will provide improved tumor characterization. Through these radiotracers, radiation plans can employ dose painting by creating different dose levels based upon specific risk factors of the target volume. Additionally, biologic imaging during radiotherapy can allow for adaptation of the radiation plan based on response to treatment. Dose painting and adaptive radiotherapy should improve the therapeutic ratio through more selective dose delivery. The novel PET-linear accelerator hopes to combine these techniques and more by using radiotracers to deliver BgRT. The areas of radiotracer uptake will serve as fiducials to guide radiotherapy to themselves. This technique may prove promising in the growing area of oligometastatic radiation treatment. Significant challenges exist for the future of PET-guided radiotherapy. However, with the advancements being made, PET imaging is set to change the delivery of radiotherapy.

SAT534 A Rare Case of Poorly Differentiated Thyroid Cancer With Extraordinary Limitations to Treatment

Abstract Disclosure: N. Shahid: None. L. Rudman: None. H. Maldonado Rivera: None. J. Chambi-Torres: None. J.A. Gonzalez: None. S. Valepu: None. A. Barco: None. N.H. Shaaban: None. E. Angueira: None. Background: Poorly differentiated thyroid cancer (PDTC) is a rare and aggressive form of follicular epithelial cell derived thyroid carcinoma, representing 3-5% of all thyroid cancers. As a subtype, PDTC is in a category that is between well differentiated thyrocyte malignancies and undifferentiated (anaplastic) thyroid carcinomas. Current guidelines for treatment of PDTC are not well defined. Case presentation: A 56-year-old male with a history of PDTC was admitted to the hospital directly from a correctional facility due to concern for metastasis. Patient had a total thyroidectomy performed just two months ago that revealed PDTC on surgical pathology. Recommendations at that time were to complete a full body PET-CT and follow up with radiation oncology for radiation and chemotherapy. Patient was also discharged on Synthroid 175 mcg daily for TSH suppression. However, the patient did not have any follow up appointments scheduled while at the facility. PET-CT showed stable FDG avid 2.4 cm lower right neck mass and 2 cm focus of mildly increased activity in the right lobe of the liver. On admission, a triple phase MRI liver protocol was ordered and showed a 15 mm hepatic lesion that was arterially enhancing with persistent enhancement in venous and delayed phase without dropping signal on T2 fat and additional hyperintensity on T2. Bilateral 1.7 cm adrenal nodule was also identified with relative hypointensity on T2. FNA of right neck mass was performed but did not yield sufficient tissue for pathology. Subsequent right neck exploration and skin biopsies were obtained and revealed benign fibroadipose tissue with focal fat necrosis in the thyroid and lobular capillary hemangioma in right back, left chest, and right abdomen. Patient’s status as an inmate continued to delay radiation and chemotherapy for PDTC with possible metastasis. The decision was made with the hematology/oncology inpatient consult team to perform RAI treatment with 138 mCI of I-131. Synthroid was held in anticipation of the RAI and whole body scan was ordered for 1 week after administration of I-131. Post ablation whole body scan showed intense radiotracer uptake over the region of the left and right thyroid glands and normal uptake in the stomach, small bowel, and urinary bladder. No other areas of radiotracer uptake were found. Conclusion: Diagnosis and treatment of PDTC is challenging and the social constraints as an inmate make it even more difficult to initiate appropriate therapy with radiation oncology follow up. Our case illustrates the implications of RAI ablation after total thyroidectomy in staging and therapy of PDTC. Given the intermediate histologic characteristics of PDTC, further investigation is required in the setting of metastasis and exploration of the benefits of early aggressive therapy, such as external beam radiotherapy. Presentation Date: Saturday, June 17, 2023

Study of PSMA-targeted 18F-DCFPyL PET/CT in the evaluation of men with an elevated PSA following radical prostatectomy.

299 Background: Positron emission tomography/x−ray computed tomography (PET/CT) utilizing radiotracers targeting prostate membrane specific antigen (PSMA) offer the promise of improved sensitivity for visualizing low volume sites of prostate cancer. In this study we evaluated the sensitivity of PET/CT using 18F-DCFPyL, a novel small molecule ligand of PSMA, for imaging sites of disease in men with an elevated PSA following radical prostatectomy. Methods: Patients with an elevated PSA following radical prostatectomy (defined as ≥ 0.2 ng/mL) were imaged with CT or magnetic resonance imaging (MRI) of the abdomen and pelvis, 99mTc-methylene diphosphonate bone scan and 18F-DCFPyL PET/CT. Conventional imaging studies (CT, MRI and boen scan) were clinically reviewed by readers blinded to the PET/CT scan results. Similarly, PET/CT scans were blindly reviewed and then the sensitivity of this novel imaging test was compared to that of conventional imaging. Results: In total, 12 men with a median PSA of 0.34 ng/mL (range 0.2 to 11) were imaged as part of this study. 2 (16.7%) patients had persistently elevated PSA values after surgery and 10 (83.3%) had values which were initially undetectable but then rose to ≥ 0.2 ng/mL. On conventional imaging, only 4 (25.0%) patients had at least 1 detectable site of disease. This included 1 patient with a local recurrence detected on MRI and 3 patients with bony lesions detected on bone scan. In contrast, 9 (75.0%) patients had areas of detectable disease on PET/CT. This included 3 (25.0%) patients with a local recurrence, 3 (25.0%) with lymph node metastases, 2 (16.7%) with bony lesions and 1 (8.3%) with both lymph node and bone findings. All lesions detected on conventional imaging had corresponding areas of radiotracer uptake on PET/CT. Conclusions: 18F-DCFPyL PET/CT appears to be more sensitive for detecting areas of prostate cancer recurrence in patients with an elevated PSA following radical prostatectomy. Future work aims to more precisely define the sensitivity of this imaging test in a larger patient cohort. Clinical trial information: NCT02523924.