2026 Proffered Presentations
S161: OLFACTORY NEUROBLASTOMA ASSESSMENTS BY MRI AND 68GA-DOTATATE PET/CT
Matheus Sewastjanow-Silva1; Maria Catalina Espinosa2; Alexander Khalaf1; Yoko Takahashi1; Ehab Hanna1; Shirley Y. Su1; 1The University of Texas MD Anderson Cancer Center; 2University of Colorado
Background: Olfactory Neuroblastoma (ONB), or esthesioneuroblastoma, is a rare sinonasal neuroectodermal tumor avid on somatostatin receptor-based molecular imaging that may exhibit distant metastases in 20% to 48% of the cases. Therefore, imaging plays an essential role throughout the prolonged monitoring of both locoregional and metastatic territories.
In the setting of ONB, magnetic resonance imaging (MRI) is favored over computed tomography (CT) due to its superior anatomic contrast and increased sensitivity in identifying perineural dissemination, intracranial extension, orbital involvement and intracranial tumoral cysts. Positron emission tomography (PET)/CT has been a useful complement when MRI findings are equivocal as well for the detection of distant metastases. As ONBs express a high level of somatostatin receptors (SSTR), functional SSTR imaging, specifically with Gallium-68 (68Ga)-DOTATATE PET/CT, is crucial.
Given the advantages and pitfalls of MRI and 68Ga-DOTATATE PET/CT we sought to evaluate the synergies and differences between the two techniques for the assessment of ONBs.
Methods: The medical records of patients with ONB seen at the University of Texas MD Anderson Cancer Center were retrospectively reviewed. Those who had both a 68Ga-DOTATATE PET/CT exam and a brain, facial or orbits magnetic resonance imaging scan within four weeks of each other, regardless of the order of the exams, were eligible for further analysis. Accuracy of the imaging exams was determined by subsequent results from further imaging or pathological assessment.
Results: Sixty-one patients met the inclusion criteria, yielding 298 pairs of consecutive MRI and 68Ga-DOTATATE PET/CT scans: a total of 596 exams performed between June 2020 and September 2025. Both imaging modalities had the same number of true negatives (n=140) and false positives (n=1); however, MRI had slightly lower rates of true positives (n=153, in comparison to 156 from 68Ga-DOTATATE PET/CT) due to a higher rate of false negatives, which were four in comparison to only one from 68Ga-DOTATATE PET/CT. Both techniques exhibited a high specificity (99.3%) and positive predictive value (99.4%), but 68Ga-DOTATATE PET/CT had better sensitivity (99.4% vs. 97.5%), negative predictive value (NPV, 99.3% vs. 97.2%), and accuracy (99.3% vs. 98.3%). When compared to MRI, the 68Ga-DOTATATE PET/CT exam showed a 75% relative improvement in avoiding missed (false negative) instances, with a number needed to test of 52. Nonetheless, PET’s numerical superiority was not statistically significant: NPV p = 0.205 (Fisher’s exact test) and sensitivity p = 0.091 (Z-test). Minimum malignant lesion sizes captured were 2 millimeters by MRI and 4 millimeters by PET. Furthermore, the 68Ga-DOTATATE PET/CT first captured seven occurrences of distant metastases that were not priorly seen by any other imaging exam.
Conclusions: In the context of diagnosis and follow-up of ONBs, where a false negative imaging result can be catastrophic, 68Ga-DOTATATE PET/CT presents as a valuable complement to MRI by diminishing the rates of missed cases as well as picking up distant metastases, thus better supporting clinical decision-making and cancer care.