Sinonasal cancers are uncommon malignancies with a generally unfavorable prognosis, often presenting at an advanced stage. Their high rate of recurrence supports close imaging surveillance and the utilization of functional imaging techniques. Whole-body ¹⁸F-FDG PET/CT has very high sensitivity for the diagnosis of sinonasal malignancies and can also be used as a “metabolic biopsy” in the characterization of some of the more common subgroups of these tumors, though due to overlap in uptake, histological confirmation is still needed. For certain tumor types, radiotracers, such as ¹¹C-choline, and radiolabeled somatostatin analogs, including ⁶⁸Ga-DOTATATE/DOTATOC, have proven useful in treatment planning and surveillance. Although serial scans for posttreatment surveillance allow the detection of subclinical lesions, the optimal schedule and efficacy in terms of survival are yet to be determined. Pitfalls of ¹⁸F-FDG, such as post-surgical and post-radiotherapy crusting and inflammation, may cause false-positive hypermetabolism in the absence of relapse.

Background: Indices of tumor heterogeneity on somatostatin receptor PET/CT scans may potentially serve as predictive biomarkers of treatment efficacy in neuroendocrine tumor (NET) patients undergoing [¹⁷⁷Lu]Lu-DOTA-TATE PRRT. Methods: NET patients who underwent [¹⁷⁷Lu]Lu-DOTA-TATE therapy at the University of Iowa from August 2018 to February 2021 were retrospectively evaluated. Radiomic features on the pre-PRRT somatostatin receptor PET/CT were evaluated using a custom MIM Software® LesionID workflow. Conventional PET/CT metrics of tumor burden, such as somatostatin receptor expression and tumor volume, were calculated in addition to the indices of tumor heterogeneity for each lesion (intra-lesional) and then summarized across all lesions throughout the body (inter-lesional). Endpoints included post-PRRT 24-month time to progression (TTP) and overall survival (OS). Cox regression models were used to assess the predictive ability of the imaging factors on post-PRRT 24-month TTP and OS. LASSO-penalized Cox regression was used to build a multivariable model for each outcome. Results: Eighty patients with a mean age of 65.1 years were included, with most (71.3%) completing 4 cycles of PRRT. Median TTP was 19.1 months, and OS at 60 months was 50%. A large degree of variability between patients was evidenced for imaging features related to somatostatin receptor expression. On multivariable analysis, total receptor expression and mean liver-corrected SUVmean were selected for 24-month TTP. The model was not able to significantly predict progression (C-statistic = 0.58, 95% CI 0.50–0.62). Total receptor expression and mean skewness were selected for OS. The resulting model was able to significantly predict death (C-statistic = 0.62, 95% CI 0.53–0.67), but the predictive ability was limited, as evidenced by the low C-statistic. Conclusions: Our exploratory analysis provides preliminary results showing that imaging indices of inter- and intra-tumor heterogeneity from pretreatment PET/CT images may potentially predict treatment efficacy in NET patients undergoing [¹⁷⁷Lu]Lu-DOTA-TATE therapy. However, prospective evaluation in a larger cohort is needed to further assess whether a comprehensive characterization of tumor heterogeneity within a patient can help guide treatment decisions.

Radium-223 dichloride (Ra-223) is now frequently used to treat prostate cancer that has metastasized to bone, although patient selection continues to be suboptimal for determining who will benefit most from this novel treatment modality. Seventy-nine patients with metastatic castration-resistant prostate cancer (mCRPC) were treated with Ra-223 from 2012 to 2016. The burden of skeletal metastasis was determined for each using the Bone Scan Index (BSI) as a ratio of diseased to normal bone. Clinical, laboratory, and survival data were collected and examined for associations with BSI, and treatment tolerability was assessed. Chemotherapy-naïve patients were significantly more likely to complete the full course of treatment. Median follow-up was 31 months (range 0.7-38.8 months) and median overall survival was 15.4 months (range 9.5-20.6 months). Overall survival was significantly associated with findings on bone scans (P < .05). Patients with higher BSI tended toward poorer outcomes. Nearly half the patients with low baseline BSI survived 3 years or more following Ra-223 treatment. By contrast, only 20% of the patients with high baseline BSI lived for 1 year, and none lived for an additional 3. Baseline BSI was significantly associated with decreased hemoglobin, higher serum PSA and alkaline phosphatase levels, and treatment-associated reductions in platelet and absolute neutrophil counts. Our results suggest better outcomes to Ra-223 therapy for patients who are chemotherapy-naïve and who undergo treatment earlier in the course of their disease as reflected by low BSI and concordant laboratory parameters.

Paraneoplastic syndromes (PNSs) are pathologic conditions produced by neoplasms not attributable to tumor invasion or metastasis. The clinical manifestations of PNSs can precede the diagnosis; these symptoms may serve as early indicators of underlying malignancy. Standard imaging modalities, such as computed tomography (CT) and magnetic resonance imaging (MRI), have limited sensitivity in detecting small or early-stage PNS-associated tumors. FDG PET/CT identifies hypermetabolic lesions suggestive of malignancy and, therefore, facilitates early diagnosis, refined treatment planning, and potentially prolonged patient survival. This review evaluates the diagnostic accuracy, clinical utility, and emerging role of FDG PET/CT in detecting occult malignancies. Syndrome-targeted applications discussed include limbic encephalitis, cerebellar degeneration, Lambert-Eaton myasthenic syndrome, Cushing’s syndrome, hypercalcemia of malignancy, dermatomyositis, and tumor-induced osteomalacia. In addition, the limitations of FDG PET/CT, including false-positive or false-negative findings, are reviewed, while newer PET tracers, like ⁶⁸Ga-DOTATATE, are also highlighted. Ultimately, FDG PET/CT has transformed clinical decision-making, enabling more timely interventions and improved patient management in the context of PNSs. Future directions in imaging, including PET/MRI and ongoing refinements in tracer design, promise to further enhance diagnostic precision, and therapeutic outcomes are also discussed.

Meckel's scan can be positive in cases of enteric duplication cyst and reveals a focus of progressively intense radiotracer uptake in the abdomen, coinciding with the appearance of activity in the stomach, suggesting ectopic gastric mucosa within the loops of bowel.