Diagnostic Utility of 68-Gallium DOTATATE PET in the Diagnosis and Management of Somatostatin Receptor Positive Skull Base Tumors

There is a strong need for the development of highly sensitive and specific imaging techniques in the diagnosis and management of skull base tumors, particularly in guiding surgical treatment planning and differentiating postoperative recurrence from treatment related change. Sensitivity and specificity of F-18-FDG PET is limited, especially in the postoperative setting. Ga-68-DOTATATE is a highly sensitive and specific PET radiotracer targeting somatostatin receptor 2 (SSTR2), and has entered clinical practice for the management of gastrointestinal neuroendocrine tumors. Several tumors involving the skull base express SSTR2 and are thus promising targets for Ga-68-DOTATATE PET; however, the clinical utility has to date not been explored. We present three cases in which Ga-68-DOTATATE PET demonstrated significant diagnostic utility.

A 68-year-old female presented with hyposmia. MRI demonstrated an infiltrative mass in the superior nasal cavity with intracranial extension through the cribriform plate. The patient underwent resection with pathology yielding esthesioneuroblastoma, Hyams grade II, KADISH Stage C. The patient received postoperative chemoradiation with VP16/cisplatin. Follow-up 18-FDG PET/CT 30 months of postresection demonstrated bilateral multilevel FDG-avid lymph nodes, suspicious for metastatic disease. Patient underwent bilateral neck dissections demonstrating metastatic esthesioneuroblastoma. Two-month postoperative follow-up CT demonstrated a new small left level IV cervical node, concerning for metastasis. Ga-68-DOTATATE PET/CT (5.07 mCi Ga-68-DOTATATE dose, imaged 45 minutes postinjection) was performed demonstrating intensely DOTATATE-avid bilateral level IV nodes (SUVmax 18.1), consistent with bilateral nodal metastases ([Fig. 1]).

A 50-year-old female presented with history of multiple glomus tumors, initially diagnosed during work up of left arm hemiparesis and pulsatile tinnitus. Patient underwent treatment to a left glomus jugulare tumor with fractionated stereotactic radiosurgery (SRS), 39.6 cGy in 22 fractions. Follow-up serial MRIs were performed, demonstrating slow growth over time. Ga-68-DOTATATE PET/CT (3.67 mCi Ga-68-DOTATATE dose, imaged 44 minutes post injection) was performed demonstrating multiple bilateral intensely DOTATATE avid foci in the skull base and neck (SUVmax 188.8), consistent with paragangliomas ([Fig. 2]), some of which had never been identified on prior imaging, including a right glomus faciale (SUVmax 11.7) and aortic body paraganglioma (SUVmax 40.1).

An 86-year-old male presented with an incidentally detected left frontal mass. Patient underwent resection with pathology yielding atypical meningioma, WHO grade II. Patient received fractionated SRS, 27 Gy in 3 fractions of 9 Gy each. Follow-up MRI demonstrated enlarging masses involving the anterior falx, right petrous apex and left temporal lobe, suspected to reflect recurrent tumor versus possible radiation necrosis. Ga-68-DOTATATE PET/MRI (4.19 mCi Ga-68-DOTATATE dose, imaged 17 minutes postinjection, 3T PET/MRI scanner) was performed demonstrating intense DOTATATE avidity in all masses, compatible with recurrence. Notably, a mass within the cerebellopontine angle cistern demonstrated markedly intense DOTATATE avidity (SUVmax 111.8), extending homogeneously to include the petrous apex, confirming osseous invasion ([Fig. 3]).

In conclusion, these cases highlight the potential utility of Ga-68-DOTATATE PET in patients with skull base tumors by providing noninvasive confirmation of metastatic disease, recurrence, and osseous invasion, thereby guiding treatment planning.