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Introduction/Justification: Adenoid cystic carcinoma (ACC) is a tumor of the salivary glands, characterized by insidious growth, recurrences, and distant metastases. Objectives: This study aimed to describe the findings of PET/CT images performed with 18 F-FDG (FDG PET/CT) and 18 F-PSMA-1007 (PSMA PET/CT) in patients with relapsed ACC to verify whether any of these studies are more suitable for identifying local recurrence and distant metastases. Materials and Methods: Patients were submitted to restaging PET/CT studies with 18 F-FDG and 18 F- PSMA-1007 with a 24-hour interval between exams before treatment. Two nuclear medicine physicians compared imaging findings. Results: Patient 1. P.A.C., a 29-year-old female, was diagnosed with ACC of the parotid in 2016. She underwent total parotidectomy and RT. In 2021, a chest computed tomography (CT) identified lung nodules, and the patient underwent resection of the largest lesions. In 2024, the patient was submitted to restaging images with FDG PET/CT that were negative for metastases, but PSMA PET/CT images identified mild PSMA uptake in two pulmonary nodules (0.8 cm, SUV = 2.2; 0.9 cm, SUV = 3.4) suspicious for ACC metastases. The patient remains asymptomatic under supervised follow-up. Patient 2. L.C.O., a 49-year-old male with newly diagnosed ACC in the salivary gland, underwent tumor resection and RT in 2010. The patient recurred in lungs and skull and was submitted to resection of the lung nodules and total skull radiotherapy (RT). In 2022, the patient underwent RT to a metastasis in the 5th lumbar vertebrae. In 2023, FDG PET/CT revealed hypermetabolism in multiple pulmonary nodules (the largest measuring 1.8 cm, SUV = 13.4) and in the L5 vertebrae (SUV = 8.5), consistent with metastases. The PSMA PET/CT showed only mild PSMA uptake in the pulmonary nodules (the largest nodule had a SUV = 4.7) and similar PSMA uptake (as FDG) in L5 vertebrae (SUV = 8.7). The patient is currently asymptomatic. Patient 3. P.C.S., a 46- year-old male, was diagnosed with ACC in the parapharyngeal space and underwent surgical resection followed by RT in 2008. In 2022, a chest CT identified lung metastases, the largest nodule with 3.8 cm. In 2023, a FDG PET/CT demonstrated hypermetabolic lung nodule metastases (the largest measuring 3.0 and 3.8 cm; SUV = 12.3 and SUV = 6.1, respectively). The FDG PET/CT also demonstrated multiple liver nodules (the largest measuring 2.7 cm) without FDG uptake, suspicious for metastases. A PSMA PET/CT showed PSMA uptake in the same lung nodules, however incongruent when compared to FDG uptake: the two nodules measuring 3.0 and 3.8 cm had SUVs of 5.2 and 8.8, respectively). The patient currently reports dyspnea during moderate-intensity physical activity. Conclusion: The data show heterogeneity in FDG PET/CT and PSMA PET/CT findings in relapsed ACC. Combining both PET/CT radiotracers can provide additional information for monitoring patients. PSMA PET/CT has the advantage of the possibility of a theranostic approach. Acknowledgements: The study was supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Fundação de Apoio ao Ensino e à Pesquisa do Estado de São Paulo (Cancer Theranostics Innovation Center, CEPID FAPESP #2021/10265-8), and International Atomic Energy Agency (IAEA) technical cooperation projects for development of Latin American Countries (IAEA/TCLAC: EX-BRA6033-2401375).

Introduction/Justification: Recently, the tracer Prostate Specific Membrane Antigen (PSMA), which can be labeled with the radioisotopes 68Ga or 18F, has been commercially introduced. Theoretically, as the name suggests, it is a substance specific to the membrane of prostate cells and prostate cancer. However, several studies have shown that it is also a marker of neoangiogenesis, leading to its uptake in various other neoplasms and benign diseases. Objectives: This study aims to evaluate the utility of radiolabeled PSMA in detecting desmoid tumors, comparing it to 18F-luorodeoxyglucose (FDG). Materials and Methods: Three participants with a confirmed diagnosis of desmoid tumor underwent PET/CT examinations with 18F-PSMA and 18F-FDG, with a maximum interval of 3 days between examinations. Images were visually compared lesion by lesion and the maximum standardized uptake value (SUV) was calculated for each lesion and each radiopharmaceutical. Results: All lesions presented uptake of both 68Ga-PSMA and 18F-FDG. In the first patient, 3 lesions were identified: a mass adjacent to the pancreas measuring 5.4 cm (FDG: SUV = 2.0) (PSMA: SUV = 8.2), a mass in the right iliac fossa measuring 7.7 cm (FDG: SUV = 3.8) (PSMA: SUV = 5.7), and another involving the duodenojejunal transition measuring 4.1 cm (FDG: SUV = 1.9) (PSMA: SUV = 3.7). In the second patient, a mass was identified adjacent to the head and uncinate process of the pancreas measuring 9.2 cm (FDG: SUV = 9.8) (PSMA: SUV = 6.1). In the third patient, an irregular retroperitoneal mass was identified at the level of the aortic bifurcation (FDG: SUV = 2.3) (PSMA: SUV = 2.4). Conclusion: Desmoid tumors can demonstrate uptake of both 68Ga-PSMA and 18F-FDG. The intensity of tracer uptake in the lesions is variable, with some showing greater uptake of FDG, others of PSMA, suggesting a potential complementary role for these radiotracers in desmoid tumors.

Introduction/Justification: Lung cancer remains a major global cause of mortality. While 18F-FDG PET/CT is widely utilized for detection, staging, and monitoring, detecting increased glucose metabolism in tumor cells, it lacks theranostic potential. The prostate-specific membrane antigen (PSMA) tracer, initially linked to prostate cancer, is also recognized as a marker of neoangiogenesis, accumulating in various neoplasms and showing promising theranostic capabilities. Objectives: This study aims to compare the uptake patterns of 18F-FDG and 18F-PSMA in primary and metastatic lesions of non-small cell lung cancer. Materials and Methods: Four male patients diagnosed with non-small cell lung cancer (including two adenocarcinomas, one squamous cell carcinoma, and one unspecified type), aged between 58 and 71 years, underwent PET/CT imaging. 18F-FDG PET/CT scans were performed 60 minutes after intravenous administration of 0.1 mCi/kg of 18F-FDG, while 18F-PSMA PET/CT scans were obtained 90 minutes after intravenous injection of 0.1 mCi/kg of 18F-PSMA. Imaging data were analyzed by two nuclear medicine physicians and one radiologist. The maximum standardized uptake value (SUVmax) of each lesion was measured for both radiotracers in the primary tumor, lymph nodes, and metastatic sites identified through visual analysis, considering values obtained above the cardiac blood pool measured in the left atrium. Results: A total of 100 lesions were detected, with 82 identified using 18F-FDG and 92 using 18F-PSMA. Eight lesions were exclusively detected by 18F-FDG, while 14 were only identified by 18F-PSMA. The median SUVmax of lesions in 18F-FDG and 18F-PSMA images was 5.3 (1.7 – 25.0) and 3.7 (0.7 - 12.4), respectively. Brain lesions were more readily identified on 18F-PSMA images, whereas liver lesions were more notable on 18F-FDG images due to the intense physiological uptake of 18F-FDG and 18F-PSMA in the brain and liver, respectively. Conclusion: Both 18F-FDG-PET/CT and 18F-PSMA-PET/CT have the ability to identify most lesions of non-small cell lung cancer. Although 18F-PSMA images detected a greater number of lesions, the uptake intensity is generally higher with 18F-FDG. These findings suggest that the two radiopharmaceuticals may have complementary roles in lung cancer by independently detecting lesions with higher glycolytic activity or greater neoangiogenesis, or both simultaneously, which could contribute to a more personalized approach in managing these patients. The results also suggest a possible theranostic approach in selected patients with high uptake of PSMA. Further investigations involving a larger patient cohort are essential to validate these findings.

Introduction/Justification: Head and neck squamous cell carcinoma (HNSCC) is a health problem worldwide. Most patients with HNSCC have locally advanced disease, and progression or relapse of the tumor after treatment are common events. Imaging exams to assess the existence and/or extent of the tumor play a crucial role in managing these patients. 18 F-FDG and 18 F-PSMA-1007 are markers of glycolytic activity and neo angiogenesis, respectively. The PET/CT images performed with 18 F-FDG (FDG PET/CT) have unequivocal contribution in HNSCC, but the importance of the images with 18 F-PSMA- 1007 (PSMA PET/CT) in tumor is still unclear. Objectives: The aim of this study was to describe the findings of FDG PET/CT and PSMA PET/CT in patients with advanced locoregional HNSCC at diagnosis or relapse with the purpose of verifying whether any of these exams is more suitable for detecting the tumor. Materials and Methods: Patients with advanced locoregional HNSCC at diagnosis or relapse of HNSCC were enrolled in study. Patients who underwent surgical resection of the tumor or treatment with radio chemotherapy in the last six months were excluded from the study. All patients were submitted to FDG PET/CT and PSMA PET/CT with a 24-hour interval between exams. Two nuclear medicine physicians and one radiologist analyzed the images. Comparisons between groups were analyzed by t-test, and differences were significant when p-values were < 0.05. Results: Five patients (three patients at diagnosis and one relapsed patient) were analyzed by both PET/CT images. The median age of patients was 60 years old (variation: 52-75), four were males and 1 was female. Most patients were smokers/ex- smokers and/or drinkers/ex-drinkers, had good performance status (ECOG 0), and presented tumors at stage IV. The primary tumor was localized in oropharynx/larynx (with lymph node isease), and relapses were seen mainly in lungs, liver, and bone. The HNSCC lesions were typically characterized by FDG uptake, but most lesions also exhibited varying degrees of PSMA uptake. In primary tumors and lymph node disease, mean ± SD and median (min-max) values of SUV found with FDG PET/CT scan at 1 hour were 21.1 ± 7.6 and 21.0 (14.0-33.1) and 9.0 ± 6.1 and 7.2 (2.7-18.8), respectively. For PSMA PET/CT scan, mean ± SD and median (min-max) values of SUV at 1 hour in primary tumors and lymph nodal disease were 4.0 ± 1.0 and 3.7 (2.9-5.3) and 9.0 ± 6.1 and 7.2 (2.7-18.8), respectively. The values of FDG uptake were higher than values of PSMA uptake in both primary tumors (p = 0.001) and lymph nodes (p = 0.02). Conclusion: HNSCC lesions were better detected by PET/CT images with 18F-FDG than with 18 F-PSMA-1007. The uptake of both markers in most tumors indicates that glycolytic activity and neoangiogenesis occur in HNSCC, enabling a more personalized approach in patient management. Nevertheless, the current study's sample size was small to draw conclusive results. Acknowledgements: The study was supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Fundação de Apoio ao Ensino e à Pesquisa do Estado de São Paulo (Cancer Theranostics Innovation Center, CancerThera, CEPID FAPESP #2021/10265-8), nd International Atomic Energy Agency (IAEA) technical cooperation projects for development of Latin American Countries (IAEA/TCLAC: EX-BRA6033-2401375).

Introduction/Justification: We have recently demonstrated a 18F-FDG PET/CT image pattern of brain metabolic redistribution from the neocortex to evolutionary ancient brain structures during the acute phase of COVID-19 respiratory syndrome (1). We report here a patient with extensive lesions caused by Hodgkin's lymphoma whose PET/CT demonstrated changes in the cerebral distribution of FDG, with reduced uptake in the neocortex and a relative increase in the basal ganglia, similar to that observed in acute COVID-19 (1). Report: A 57-year-old female patient with a history of hypertension and hypothyroidism, presented with weight loss and generalized lymphadenopathy. Biopsy revealed nodular sclerosis classical Hodgkin's lymphoma subtype. 18F-FDG PET/CT was requested for staging. The images showed marked hypermetabolism in lymphadenopathy below and above the diaphragm, spleen, and bone marrow, consistent with lymphoma infiltration. Reduced radiotracer uptake was also observed in the cerebral neocortex and relatively increased uptake in the basal ganglia. Semiquantitative analysis of FDG uptake in multiple brain regions was conducted using dedicated software, and the standard deviation (SD) of brain uptake in each region was calculated compared to a normal database, using the whole brain as the reference region for normalization. Quantification revealed marked increased relative uptake in lenticular nuclei (13.7 SD), thalamus (4.6) and brainstem (3.7), and reduced uptake in the frontal, parietal, and temporal lobes (-3,9 to -0,1 SD). Before starting chemotherapy, the patient experienced weakness, multiple episodes of diarrhea, and decreased level of consciousness. She developed hemophagocytic syndrome, septic shock, and died 19 days after PET/CT. Aggressive lymphomas exhibit intense FDG uptake, often with a high tumor burden. This can elevate blood lactate levels, which would become an alternative energy substrate for the brain and, by competition, reduce FDG uptake, as suggested by Yi HK et al (2). This is also described in individuals engaged in intense exercise, where decreased FDG uptake may be attributed to potential lactate utilization by the brain (3). The relatively preserved FDG uptake in the basal ganglia could be viewed as a physiological protective mechanism in response to reduced glucose availability for the brain. The oldest parts of the brain are vital for survival and must be preserved to maintain essential life functions. Despite being an organ with one of the highest glucose demands, the brain lacks the ability to store metabolic products for later use. Therefore, during competition with neoplastic cells for the available energy substrate, metabolic redistribution could contribute to preserving essential brain functions. Conclusion: Patients with high tumor burden due to Hodgkin's lymphoma may exhibit not only a global reduction in cerebral glucose uptake but also a redistribution of glucose consumption from the neocortex to older brain structures which are essential for survival.

Introduction/Justification: Myelofibrosis, a clonal disorder of hematopoietic stem cells, is characterized by chronic bone marrow inflammation and progressive fibrosis, resulting in hypocellularity and the displacement of neoplastic cells to extramedullary organs such as the spleen and liver, leading to splenomegaly and hepatomegaly. Hematopoietic stem cell transplantation is currently the only curative treatment, with five-year survival rates ranging between 51% and 61%, underscoring the need for novel diagnostic and therapeutic strategies. In recent years, positron emission tomography combined with computed tomography (PET/CT) using 18F-fluorodeoxyglucose (18F-FDG) has emerged as a valuable tool for assessing the glycolytic activity of various neoplasms, although there are limited reports on its utility in myelofibrosis. Concurrently, interest has grown in using the prostate-specific membrane antigen (PSMA) tracer to evaluate the neoangiogenic activity of diverse neoplasms. This study aims to compare glycolytic activity and neoangiogenic activity, assessed through 18F-FDG and 18F-PSMA PET/CT imaging, respectively, in patients with myelofibrosis. Report: Three patients diagnosed with myelofibrosis, aged 69, 71, and 74 years, underwent PET/CT scans on consecutive days, acquired 60 minutes after intravenous administration of 0.1 mCi/kg of 18F-FDG and 90 minutes after intravenous injection of 0.1 mCi/kg of 18F-PSMA. The images were analyzed by two nuclear medicine physicians and a radiologist. The maximum standardized uptake value (SUV) of the bone marrow, as well as the SUV and dimensions of the liver and spleen, were measured. Two patients exhibited mild to moderate diffuse increased uptake of both 18F-FDG and 18F-PSMA in the bone marrow (SUV-FDG: 6.4 and 3.5; SUV-PSMA: 3.5 and 1.7). One of them displayed mild hepatomegaly (18.7 cm), and both had marked splenomegaly (21.5 and 30.3 cm). Liver and spleen uptake of 18F-FDG was close to normal in both patients (SUV-FDG: 2.4 to 3.1), while moderate uptake of 18F-PSMA was observed in these organs (SUV-PSMA: 5.6 to 8.4), at least partially physiological and expected for this radiopharmaceutical. The third patient, who had undergone splenectomy, did not exhibit significant uptake of either tracer in the bone marrow but displayed marked uptake of 18F-PSMA in the liver (SUV-PSMA = 14.8), possibly physiological, with normal 18F-FDG uptake (SUV-FDG = 3.9). Conclusion: Patients with myelofibrosis appear to exhibit variable degrees of glycolytic activity and neoangiogenesis in the bone marrow, as detected by PET/CT imaging with 18F-FDG and 18F-PSMA. The moderate to marked uptake of 18F-PSMA in the liver and spleen, at least partly physiological, along with the uptake in the bone marrow in some cases, may suggest a theranostic potential of this radiopharmaceutical in myelofibrosis.