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Dostarlimab is an immune checkpoint inhibitor (ICI) targeting the Programmed-Death-1 (PD-1) co-receptor, recently approved by the European Medicines Agency (EMA) and the Food and Drug Administration (FDA) as a novel therapy for recurrent or advanced endometrial cancer. We report the case of a 64-year-old woman, experiencing vaginal recurrence with microsatellite instability high/hypermutated of a FIGO stage IA grade 2 endometrial endometrioid adenocarcinoma. She received preoperative chemotherapy with four cycles of carboplatin plus paclitaxel, with stable disease on pelvic magnetic resonance imaging (MRI) and fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG PET/CT). Dostarlimab (500 mg intravenously every 3 weeks) was then introduced. The subsequent evaluation after three perfusions demonstrated a complete metabolic response on 18F-FDG PET/CT according to immunotherapy-modified PET response criteria in solid tumors (imPERCIST) criteria, then confirmed by MRI according to immune response evaluation criteria in solid tumors (iRECIST). This clinical description suggests that 18F-FDG PET/CT might take place among available tools for guiding the preoperative management for recurrent endometrial cancer patients receiving dostarlimab immunotherapy that should be further explored through clinical trials.

Worldwide deployment of COVID-19 vaccines is in progress. Recent immune activation following vaccination can sometimes be seen in fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography ([18F]-FDG PET/CT). As previously evidenced, FDG-avid axillary lymph node(s) are common in patients receiving vaccines against SARS-CoV-2, influenza virus, or human papillomavirus, and reflect a regional immune response. In addition, these findings may also be accompanied by an increased spleen glucose metabolism after the COVID-19 vaccine, which captures a systemic immune response. Hence, we provide here a clinical example demonstrating that immune response could be associated with increased glucose metabolism in lymphoid organs such as lymph nodes and the spleen, which are critical modulators of T cell immunity. We believe that it is of paramount importance that nuclear physicians should be able to recognize clinical and imaging features of such immune responses upon vaccination for COVID-19 and beyond.

Early detection of immune-related adverse events (irAEs) with immune checkpoint inhibitors (ICIs) is crucial, particularly when these are likely to mimic tumor progression, as well as sarcoid-like reactions. Here, we report the case of a 68-year woman, with a history of four primary cutaneous melanomas (thickest lesion with BRAF mutation removed from the left axilla 2 years before), who was diagnosed with BRAF V600E-mutant metastatic melanoma and treated by ICI targeting the PD-1 receptor. Follow-up whole-body positron emission tomography/computed tomography (PET/CT) using 18F-fluorodeoxyglucose ([18F]-FDG) was performed at 15 months, and FDG-avid subcutaneous nodules on her legs were detected. A biopsy from a lesion on her right leg was obtained, and histology strongly suggested erythema nodosum. Given the isolated nature of these lesions, the normal serum Angiotensin-Converting Enzyme and the context of ICI, an immune-related sarcoid-like reaction was retained as the most likely diagnosis. Recent literature in immune-oncology suggests that erythema nodosum could be directly related to ICI(s). Although erythema nodosum is a rare occurrence with imaging features overlapping with malignancy, it should be considered in the differential diagnosis of suspicious in-transit metastasis, especially when the patient is treated with ICIs and when lesions follow a bilateral distribution. In conclusion, nuclear medicine physicians should keep in mind this irAE when interpreting PET/CT scans in clinical practice in order to avoid false-positive findings.