LAUSR

Meningiomas are the most common primary intracranial neoplasm. Once surgical and radiotherapeutic options are exhausted, there are no effective medical treatments available. A majority of meningiomas express somatostatin receptor 2 (SSTR2), representing a promising treatment target. 177Lu-DOTATATE is a SSTR2-targeting radionuclide that has been successful in SSTR2-expressing neuroendocrine tumors. Here we hypothesize that 177Lu-DOTATATE is effective in treating progressive intracranial meningiomas. In this ongoing phase II study (NCT03971461), adults with advanced intracranial meningiomas received 177Lu-DOTATATE 7.4 GBq (200 mCi) every 8 weeks for 4 doses. 68Ga-DOTATATE PET-MRI was obtained before and at the end of treatment (EOT). The primary endpoint was progression-free survival at 6 months (PFS-6). Correlative studies evaluated the association of PFS-6, objective response rate, progression-free survival, overall survival with radiographic tumor measurements, 68Ga-DOTATATE uptake on PET-MRI, SSTR2 expression in tumor, and meningioma methylation subclass. Nine patients (F = 7, M = 2) with progressive meningiomas (WHO I = 2, II = 6, III = 1) have been enrolled. Median age was 63 (range 49–78) years. All patients previously underwent tumor resection and at least one course of radiation. Treatment with 177Lu-DOTATATE was well tolerated, although CTCAE grade 3/4 electrolyte derangements and cytopenias were observed. Six patients reached PFS-6, three patients experienced progressive disease. Four patients had EOT 68Ga-DOTATATE PET-MRI evaluations in which anatomic measurements and 68Ga-DOTATATE standardized uptake values (SUV) pre- and post-treatment were assessed: one patient had reduced SUV measurements in all target lesions indicating altered SSTR2 expression and functional treatment response, one patient had stable disease, one patient had a mixed treatment response, and one patient experienced progressive disease. SSTR2-targeting 177Lu-DOTATATE represents a promising treatment option for patients with progressive intracranial meningiomas. Treatment is well tolerated and can lead to functional alteration of tumoral SSTR2 expression by 68Ga-DOTATATE PET-MR imaging.