The Role of 18-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (18F-FDG PET/CT) in the Diagnosis and Evaluation of Spondylodiscitis.

Spondylodiscitis, characterized by inflammation of the intervertebral disc and adjacent vertebral bodies, presents a diagnostic challenge due to its nonspecific clinical manifestations and variable imaging findings. This review examines the role of PET-CT with FDG, in the evaluation of spondylodiscitis, focusing on its utility in diagnosis, assessment of disease extent, treatment response monitoring, and prognostication. FDG PET-CT, by combining metabolic and anatomical imaging modalities, offers superior sensitivity and specificity compared to conventional imaging techniques in detecting infectious foci, distinguishing between infection and post-treatment changes, and identifying occult sources of infection. Additionally, FDG PET-CT facilitates the localization of infection, aiding in targeted biopsy and guiding surgical intervention. Moreover, quantitative PET parameters, such as standardized uptake values (SUVs), hold promise for predicting treatment response and prognosis. Despite its advantages, FDG PET-CT has limitations, including false-positive results in the setting of inflammation and limited availability in resource-constrained settings. Collaborative efforts between radiologists, nuclear medicine specialists, infectious disease specialists, and spine surgeons are essential to optimize the role of FDG PET-CT in the multidisciplinary management of spondylodiscitis. Further research is warranted to elucidate the cost-effectiveness and clinical impact of FDG PET-CT in this challenging clinical entity.

99mTc-Labeled Cyclic Peptide Targeting PD-L1 as a Novel Nuclear Imaging Probe.

Recent cancer therapies have focused on reducing immune suppression in the tumor microenvironment to prevent cancer progression and metastasis. PD-1 is a checkpoint protein that stops the immune response and is expressed on immune T cells. Cancer cells express a PD-1 ligand (PD-L1) to bind to the T-cell surface and activate immunosuppressive pathways. This study aimed to design, synthesize, and evaluate a 99mTc-labeled PD-L1-targeting cyclic peptide inhibitor (99mTc-iPD-L1) as a novel SPECT radiopharmaceutical for PD-L1 expression imaging. AutoDock software (version 1.5) was used to perform molecular docking for affinity calculations. The chemical synthesis was based on the coupling reaction of 6-hydrazinylpyridine-3-carboxylic acid with a 14-amino-acid cyclic peptide. iPD-L1 was prepared for 99mTc labeling. Radio-HPLC was used to verify radiochemical purity. The stability of the radiopeptide in human serum was evaluated by HPLC. iPD-L1 specificity was assessed by SDS-PAGE. [99mTc]Tc-iPD-L1 cellular uptake in PD-L1-positive cancer cells (HCC827 and HCT116) and biodistribution in mice with induced tumors were also performed. One patient with advanced plantar malignant melanoma received [99mTc]Tc-iPD-L1. The iPD-L1 ligand (AutoDock affinity: -6.7 kcal/mol), characterized by UPLC mass, FT-IR, and UV-Vis spectroscopy, was obtained with a chemical purity of 97%. The [99mTc]Tc-iPD-L1 was prepared with a radiochemical purity of >90%. In vitro and in vivo analyses demonstrated [99mTc]Tc-iPD-L1 stability (>90% at 24 h) in human serum, specific recognition for PD-L1, high uptake by the tumor (6.98 ± 0.89% ID/g at 1 h), and rapid hepatobiliary and kidney elimination. [99mTc]Tc-iPD-L1 successfully detected PD-L1-positive lesions in a patient with plantar malignant melanoma. The results obtained in this study warrant further dosimetric and clinical studies to determine the sensitivity and specificity of [99mTc]Tc-iPD-L1/SPECT for PD-L1 expression imaging.

Improving Overall Survival and Quality of Life in Patients with Prostate Cancer and Neuroendocrine Tumors Using 177Lu-iPSMA and 177Lu-DOTATOC: Experience after 905 Treatment Doses.

177Lu-iPSMA is a novel radioligand developed at ININ-Mexico with a high affinity for the PSMA protein heavily expressed in cancer cells of approximately 95% of patients with metastatic castration-resistant prostate cancer (mCRPC). 177Lu-DOTATOC is a patent-free radioligand, molecularly recognized by somatostatin receptors (SSTR-2) overexpressed in cancer cells of about 80% of patients with metastatic gastroenteropancreatic neuroendocrine tumors (GEP-NET). This translational research aimed to determine the efficacy and safety of 177Lu-iPSMA and 177Lu-DOTATOC developed as GMP pharmaceutical formulations for treating progressive and advanced mCRPC and NET. One hundred and forty-five patients with mCRPC and one hundred and eighty-seven subjects with progressive NET (83% GEP-NET and 17% other NET), treated with 177Lu-iPSMA and 177Lu-DOTATOC, respectively, were evaluated. Patients received a mean dose of 7.4 GBq per administration of 177Lu-iPSMA (range 1-5 administrations; 394 treatment doses) or 177Lu-DOTATOC (range 2-8 administrations; 511 treatment doses) at intervals of 1.5-2.5 months. Efficacy was assessed by SPECT/CT or PET/CT. Results were stratified by primary tumor origin and number of doses administered. Patients with mCRPC showed overall survival (OS) of 21.7 months with decreased radiotracer tumor uptake (SUV) and PSA level in 80% and 73% of patients, respectively. In addition, a significant reduction in pain (numerical scale from 10-7 to 3-1) was observed in 88% of patients with bone metastases between one and two weeks after the second injection. In the GEP-NET population, the median progression-free survival was 34.7 months, with an OS of >44.2 months. The treatments were well tolerated. Only ten patients experienced grade ≥ 3 myelosuppression (3% of all patients). The observed safety profiles and favorable therapeutic responses demonstrated the potential of 177Lu-iPSMA and 177Lu-DOTATOC to improve overall survival and quality of life in patients with progressive and advanced mCRPC and NET.

18F-FDG-PET/CT in Canine Mammary Gland Tumors.

Medical imaging techniques play a central role in clinical oncology, helping to obtain important information about the extent of disease, and plan treatment. Advanced imaging modalities such as Positron Emission Tomography-Computed Tomography (PET/CT), may help in the whole-body staging in a single procedure, although the lesions should be carefully interpreted. PET/CT is becoming commonly used in canine cancer patients, but there is still limited information available on specific tumors such as mammary cancer. We evaluated the utility of fluorine-18 fluorodeoxyglucose (18F-FDG)-PET/CT to detect malignant lesions in eight female dogs with naturally occurring mammary tumors. A whole-body scan was performed prior to surgery, and mammary and non-mammary lesions detected either on PET/CT or during pre-surgical physical exam were resected when possible and submitted for histopathological examination. Multiple mammary lesions involving different mammary glands were detected in 5/8 dogs, for a total of 23 lesions; there were 11 non-mammary-located lesions in 6/8 dogs, three of these were lung or lymph node metastasis. A total of 34 lesions were analyzed: 22 malignant (19 mammary tumors and three metastatic lesions), and 12 benign (four mammary lesions and eight of non-mammary tissues). Glucose uptake by maximum standardized uptake value (SUVmax) was analyzed and correlated with tumor size, and benign vs. malignant pathology. We found that the minimum tumor size needed to distinguish malignant lesions according to the SUVmax was 1.5 cm; benign and malignant lesions <1.5 cm did not differ in glucose uptake (mean SUVmax = 1.1). In addition, a SUVmax value >2 was 100% sensitive for malignancy. Combining these data, lesions >1.5 cm with a SUVmax >2 had a positive predictive value of 100%. Finally, we did not find an association between SUVmax and histologic subtype or grade, which may be present in a larger sample. Thus, 18F-FDG PET/CT is useful for distinguishing malignant from benign lesion but further imaging of dogs with diverse tumors, should establish characteristic SUV value cutoffs for detecting primary and metastatic disease, and distinguishing them from benign lesions.

Molecular imaging in musculoskeletal infections with 99mTc-UBI 29-41 SPECT/CT.

OBJECTIVE: To determine the added value of CT over planar and SPECT-only imaging in the diagnosis of musculoskeletal infection using 99mTc-UBI 29-4. MATERIALS AND METHODS: 184 patients with suspected musculoskeletal infection who underwent planar and SPECT/CT imaging with 99mTc-UBI 29-41 were included. Planar, SPECT-only and SPECT/CT images were reviewed by two independent analysts for presence of bone or soft tissue infection. Final diagnosis was confirmed with tissue cultures, surgery/histology or clinical follow-up. RESULTS: 99mTc-UBI 29-41 was true positive in 105/184 patients and true negative in 65/184 patients. When differentiating between soft tissue and bone infection, planar + SPECT-only imaging had a sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 95.0, 74.3, 84.8, 91.3 and 86.9%, respectively, versus 99.0, 94.5, 92.5, 98.5 and 94.5% for SPECT/CT. SPECT/CT resulted in a change in reviewers' confidence in the final diagnosis in 91/184 patients. Inter-observer agreement was better with SPECT/CT compared with planar + SPECT imaging (kappa 0.87, 95% CI 0.71-0.85 versus kappa 0.81, 95% CI 0.58-0.75). CONCLUSION: Addition of CT to planar and SPECT-only imaging led to an increase in diagnostic performance and an improvement in reviewers' confidence and inter-observer agreement in differentiating bone from soft tissue infection.

Metabolic tumor volume changes assessed by interval 18fluorodeoxyglucose positron emission tomography-computed tomography for the prediction of complete response and survival in patients with diffuse large B-cell lymphoma.

An early discrimination of survival probability is required for patients with diffuse large B cell lymphoma (DLBCL), which may identify patients that require other treatment options, for example clinical trials. To the best of our knowledge, the impact of interim evaluation with 18fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) has not yet been determined in this type of neoplasia. The aim of the present study was to determine the role of changes in metabolic tumor volume (MTV) between baseline and interim 18F-FDG PET/CT scans, following three courses of chemotherapy in order to predict complete response (CR) and overall survival (OS) in patients with DLBCL. Patients with previously untreated DLBCL who had received the standard 6-8 cycles of rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone were included in the present study. A predictive model was constructed using changes in MTV and other clinical factors including age, gender, East Cooperative Oncology Group (ECOG) status, clinical stage, B symptoms, the presence of bulky disease and elevated lactate dehydrogenase levels, and data were analyzed using logistic regression analysis. In total, 50 patients with DLBCL were included in the present study. The majority of patients presented with stage III/IV disease (64%), B symptoms (72%) and bulky disease (58%). According to the International Prognostic Index score, 44% of patients were in the intermediate-high or high-risk categories for risk of relapse, and therefore considered to have poor prognosis. In total, ≥94% of patients achieving a decrease in total MTV had a 2-year OS rate of 95%, compared with the 58% OS rate of those with a suboptimal response. A multivariate model, including a change in MTV (a decrease of ≥94%), the ECOG performance status ≥2, a change in leukocyte counts and age, was used to predict CR. This model was used to define two groups according to the predicted probability of recurrence (cutoff, 0.69). The 2-year survival rates of the two groups were 95 and 59%, respectively. Analysis of changes in MTV in the interim 18F-FDG PET/CT revealed significant prognostic value for the prediction of CR and OS in patients with DLBCL.

Comparison of Three Chemotherapy Regimens in Elderly Patients with Diffuse Large B Cell Lymphoma: Experience at a Single National Reference Center in Mexico.

Background. Although chemotherapy added to rituximab is a standard of care for diffuse large B cell lymphoma (DLBCL), treatment of patients ≥65 years of age remains controversial due to comorbidities. Methods. This is a retrospective, comparative, nonrandomized study of patients ≥65 years of age, who were diagnosed with DLBCL but not previously treated. Demographic characteristics and comorbidities were analyzed. Three rituximab-containing treatment regimens (standard RCHOP, anthracycline dose-reduced RChOP, and RCOP) were compared. Descriptive analyses were conducted. Survival was calculated with the Kaplan-Meier method, and differences were compared with the log-rank test. Results. In total, 141 patients with a median age of 73.9 years were studied. The three treatment groups had comparable demographic characteristics. The overall response was 77%, 72.5%, and 59% in groups treated with RCHOP, RChOP, and RCOP, respectively. After multivariate analysis, the factors influencing the overall survival were the presence of B symptoms, poor performance status (ECOG ≥ 3), and febrile neutropenia. Factors influencing disease-free survival were febrile neutropenia, high-intermediate and high-risk IPI scores, and treatment without anthracycline. Conclusion. A higher ORR (overall response rate) was achieved with standard RCHOP, which influenced DFS and OS, although it was not statistically significant compared with the other groups. Interventional phase 3 trials testing new molecules in patients aged 70 to 80 years and older are required to improve the prognosis within this growing population.