68GA DOTATATE PET in Schwannomas: Distinct Avidity Pattern Supporting Noninvasive Diagnosis.

BACKGROUND AND PURPOSE: Schwannomas are a key diagnostic consideration in patients with enhancing extra-axial intracranial, skull base, and neck masses. While contrast-enhanced MRI is the diagnostic mainstay, its specificity can be limited, especially in small or atypical lesions. [68GA]DOTATATE PET/MRI and PET/CT, which target somatostatin receptor subtype 2 (SSTR2), represent an established tool in evaluating SSTR2-positive tumors, most notably meningiomas and paragangliomas, entities that can mimic schwannomas on conventional MRI. However, data on SSTR2 expression in schwannomas remain limited. We aimed to characterize [68GA]DOTATATE PET imaging features in patients with imaging-defined schwannomas.

MATERIALS AND

METHODS

We retrospectively identified patients who underwent [68GA]DOTATATE PET/MRI or PET/CT for evaluation of known or suspected SSTR2-positive tumors and had MRI features diagnostic of schwannoma. PET/CT or PET/MRI was performed as part of clinical evaluation according to previously published institutional protocols. Lesion maximum standardized uptake values (SUV), superior sagittal sinus (SSS) SUV (blood pool reference), and SUV ratios relative to the SSS (SUVRSSS) were measured.

RESULTS

Sixteen patients met the inclusion criteria (mean age 62.1 ± 13.4 years; 43.8% women). The cohort included 6 patients with isolated schwannomas and 10 with concurrent meningiomas. None had prior radiotherapy. All lesions demonstrated minimal [68GA]DOTATATE avidity; the mean maximum lesion SUV was 1.6 ± 0.7, and the mean SUVRSSS was 1.5 ± 0.7, values well below established thresholds for meningioma diagnosis.

CONCLUSIONS

Schwannomas exhibit minimal [68GA]DOTATATE avidity, in contrast to SSTR2-expressing tumors such as meningiomas. [68GA]DOTATATE PET may therefore aid in noninvasively differentiating schwannomas from SSTR2-expressing tumors with overlapping MRI features in diagnostically challenging cases.