Background: our aim was to assess the diagnostic performance and clinical impact of ¹⁸F-FDG PET/CT in patients with differentiated thyroid carcinoma (DTC), previously treated with surgery and radioiodine therapy (RAI). Methods: patients subjected to ¹⁸F-FDG PET/CT for suspected DTC recurrence in three Italian nuclear medicine units were evaluated. Two different clinical settings were identified: clinical setting 1 included patients (n = 40) that were enrolled according to the American Thyroid Association guidelines (i.e., negative ¹³¹1-WBS and Tg level > 10 ng/mL); and clinical setting 2, that encompassed subjects (n = 26) with serum Tg ≤ 10 ng/mL but morphological findings suspected of relapse. PET/CT’s impact was scored as significant if it provided an indication for surgery, or led to a novel therapeutic decision. Results: In total, 51/66 patients (77.3%) were ¹⁸F-FDG positive, while 15 (22.7%) were negative. PET/CT showed an overall sensitivity and specificity of 84.4% and 75%, respectively. Sensitivity was higher in clinical setting 1 (89.1%) as compared to clinical setting 2 (76.1%), although this difference was not statistically significant (p = 0.83). PET/CT influenced clinical management in 28 cases (42.4%), without a significant difference between the 2 groups of patients (p = 0.6). Conclusions: our preliminary data, although limited by the retrospective nature of the study and possible selection bias, suggest that ¹⁸F-FDG PET/CT may be utilized for the detection of DTC recurrence in different clinical settings, with a meaningful impact on clinical management.

A 76-year-old woman affected by pancreatic neuroendocrine tumor previously subjected to surgery with progressive liver disease and a concomitant mild symptomatic meningioma of the left pontocerebellar angle underwent 4 cycles of peptide receptor radionuclide therapy with ¹⁷⁷Lu-DOTATATE. A prophylactic therapy with corticosteroids was carried out before each treatment cycle, and the neurosurgery unit was alerted in case of cerebral edema and related neurologic symptoms. A ⁶⁸Ga-DOTATOC PET/CT scan performed after the completion of the 4 cycles’ treatment documented a hepatic partial response and a substantial stability of the brain mass. No neurological complications occurred during treatment and follow-up.

The aim of this study was to develop a baseline [¹⁸F]FDG PET/CT model to predict immunotherapy response in advanced cutaneous squamous cell carcinoma (cSCC) and noninvasively determine tumor grade, thereby enhancing early patient stratification. We retrospectively analyzed 59 patients with histologically confirmed advanced cSCC submitted to immunotherapy with cemiplimab. All underwent [¹⁸F]FDG PET/CT at baseline and after approximately 12 weeks. Clinical response was assessed through PET findings integrated with clinical and dermatological evaluation, and patients were classified as responders (complete/partial metabolic response or stable disease) or non-responders (progression or toxicity-related discontinuation). Tumors were also classified as low to intermediate (G1–G2) or poorly differentiated (G3). Machine learning models (Random Forest and Extreme Gradient Boosting) were trained to predict treatment response and tumor grade. Clinical benefit was observed in 46/59 patients (77.9%), while 13 (22.1%) were non-responders. Histology showed 64.4% (n = 38) G1–G2 and 35.6% (n = 21) G3 tumors. The PET-based model best predicted clinical benefit (AUC = 0.96, accuracy = 91% cross-validation; AUC = 0.88, accuracy = 82% internal validation). For tumor grade prediction, the CT-based model achieved a higher AUC of 0.80 (accuracy 73%), whereas the PET-based model reached an AUC of 0.78 but demonstrated a slightly higher accuracy of 77%. Radiomic analysis of baseline [¹⁸F]FDG PET enables the discriminative prediction of immunotherapy response and tumor grade in advanced cSCC, with PET-based models outperforming CT-based ones.

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder characterized by extreme ultraviolet (UV) sensitivity, predisposing patients to multiple cutaneous malignancies. We present the case of a 26-year-old male with XP diagnosed with three distinct skin cancers: superficial spreading melanoma (SSM), basal cell carcinoma (BCC), and squamous cell carcinoma (SCC). Among these, the melanoma had metastasized. A computed tomography (CT) scan revealed a suspicious pulmonary nodule, prompting further metabolic characterization via positron emission tomography/computed tomography (PET/CT) with ¹⁸F-fluorodeoxyglucose ([¹⁸F]FDG). The scan detected significant hypermetabolism not only in the lung lesion but also in an unsuspected right parotid gland lesion, refining disease staging and guiding treatment decisions. The patient underwent immunotherapy with nivolumab, achieving a complete metabolic response in both metastatic lesions, as confirmed by follow-up PET/CT. This case underscores the critical role of [¹⁸F]FDG PET/CT in staging and treatment monitoring for selected patients with XP, a population in which advanced imaging is rarely employed. Moreover, the patient’s remarkable response to immunotherapy suggests a potential link between XP-related DNA repair defects and increased sensitivity to PD-1 blockade. These findings highlight the importance of integrating metabolic imaging into XP management and warrant further investigation into the immunogenicity of XP-associated malignancies.

Xeroderma Pigmentosum (XP) is a rare autosomal recessive disorder characterized by extreme ultraviolet (UV) sensitivity, predisposing patients to multiple cutaneous malignancies. We present the case of a 26-year-old male with XP diagnosed with three distinct skin cancers: Superficial Spreading Melanoma (SSM), Basal Cell Carcinoma (BCC), and Squamous Cell Carcinoma (SCC). Among these, the melanoma had metastasized. A CT scan revealed a suspicious pulmonary nodule, prompting further metabolic characterization via [18F]FDG PET/CT. The scan detected significant hypermetabolism not only in the lung lesion but also in an unsuspected right parotid gland lesion, refining disease staging and guiding treatment decisions. The patient underwent immunotherapy with nivolumab, achieving a complete metabolic response in both metastatic lesions, as confirmed by follow-up PET/CT. This case underscores the critical role of [18F]FDG PET/CT in staging and treatment monitoring for selected XP patients, a population in which advanced imaging is rarely employed. Moreover, the patient’s remarkable response to immunotherapy suggests a potential link between XP-related DNA repair defects and increased sensitivity to PD-1 blockade. These findings highlight the importance of integrating metabolic imaging into XP management and warrant further investigation into the immunogenicity of XP-associated malignancies.