Role of peripheral blood MRD and 18F-FDG PET in the post-CAR relapse setting: a case study of discordant peripheral blood and bone marrow MRD.

BACKGROUND: Chimeric antigen receptor (CAR) T cell therapy is an effective salvage therapy for pediatric relapsed B-cell acute lymphoblastic leukemia (B-ALL), yet is challenged by high rates of post-CAR relapse. Literature describing specific relapse patterns and extramedullary (EM) sites of involvement in the post-CAR setting remains limited, and a clinical standard for post-CAR disease surveillance has yet to be established. We highlight the importance of integrating peripheral blood minimal residual disease (MRD) testing and radiologic imaging into surveillance strategies, to effectively characterize and capture post-CAR relapse. MAIN BODY: Here, we describe the case of a child with multiply relapsed B-ALL who relapsed in the post-CAR setting with gross non-contiguous medullary and EM disease. Interestingly, her relapse was identified first from peripheral blood flow cytometry MRD surveillance, in context of a negative bone marrow aspirate (MRD <0.01%). Positron emission tomography with 18F-fluorodeoxyglucose revealed diffuse leukemia with innumerable bone and lymph node lesions, interestingly sparing her sacrum, the site of her bone marrow aspirate sampling. CONCLUSIONS: We highlight this case as both peripheral blood MRD and 18F-fluorodeoxyglucose positron emission tomography imaging were more sensitive than standard bone marrow aspirate testing in detecting this patient's post-CAR relapse. Clinical/Biologic Insight: In the multiply relapsed B-ALL setting, where relapse patterns may include patchy medullary and/or EM disease, peripheral blood MRD and/or whole body imaging, may carry increased sensitivity at detecting relapse in patient subsets, as compared with standard bone marrow sampling.

Management of Differentiated Thyroid Cancer: The Standard of Care.

In the past decade, the management of differentiated thyroid cancer (DTC) underwent a paradigm shift toward the use of risk stratification with the goal of maximizing the benefit and minimizing the morbidity of radioiodine (131I) therapy. 131I therapy is guided by information derived from surgical histopathology, molecular markers, postoperative diagnostic radioiodine scintigraphy, and thyroglobulin levels. 131I is used for diagnostic imaging and therapy of DTC based on physiologic sodium-iodine symporter expression in normal and neoplastic thyroid tissue. We summarize the essential information at the core of multidisciplinary DTC management, which emphasizes individualization of 131I therapy according to the patient's risk for tumor recurrence.

Pediatric Esophageal Squamous Cell Carcinoma Staged With 18F-FDG PET/CT.

A 15-year-old boy with autism and swallowing dysfunction presented with a 6-month history of fatigue, intermittent abdominal pain, and weight loss. He later became febrile and had multiple episodes of coffee ground emesis and melena stools. An upper endoscopy showed an esophageal mass, and a subsequent F-FDG PET/CT scan confirmed this finding. PET/CT also revealed metastatic disease in local lymph nodes, thus upstaging the patient and indicating poor prognosis. Consideration of these severe results and the patient's quality of life helped guide decision making in patient management, with the ultimate decision to pursue palliative care.

18F-FDG PET/CT With Diffusely High FDG Uptake Throughout Subcutaneous Adipose Tissues.

A 9-year-old girl presented with facial rash, angioedema, fevers, and night sweats. She was diagnosed with chronic active Epstein-Barr virus infection and placed on chronic steroid treatment. F-FDG PET/CT performed 3 weeks following presentation revealed diffuse subcutaneous soft tissue FDG activation throughout the entire body, with likely localization to white subcutaneous adipose tissue. This highly unusual appearance may have been due to the patient being treated with corticosteroids at the time of the scan.