Zagzag, David

Abstract BACKGROUND [68Ga]Ga-DOTA-TATE (68Ga-Dotatate) PET is a promising imaging modality for post-operative meningioma delineation and outcome assessments following stereotactic radiosurgery. However, its utility for response assessment following other meningioma therapies, including somatostatin receptor 2 (SSTR2) targeting [177Lu]Lu-DOTA-TATE (177Lu-Dotatate) therapy is insufficiently understood. Here we report the 68Ga-Dotatate PET results, prospectively obtained in patients with treatment-refractory meningioma who enrolled in a phase 2, open-label clinical trial (NCT03971461) evaluating the radiopharmaceutical 177Lu-Dotatate. METHODS Patients underwent 68Ga-Dotatate PET during screening and 24±2 weeks following treatment with 177Lu-Dotatate at 7.4 GBq (200 mCi) every 8 weeks for 4 doses. Up to 5 meningioma lesions per patient were assessed by gadolinium-enhanced T1 MRI and 68Ga-Dotatate PET using lesional Krenning score and lesional to superior sagittal sinus (SSS) maximum standardized uptake value (SUVmax) ratio (SUVR (lesion/SSS)). RESULTS Eight patients with 16 lesions were assessed. By RANO criteria, the best radiographic response was stable disease (SD) in 7 patients (14 lesions) and partial response (PR) in 1 patient (2 lesions). Krenning score was assessed in 14 lesions (Krenning 4/3/2/1 in 3/4/5/2 lesions). Following 177Lu-Dotatate, Krenning score was reduced by ≥1 point in 9 and remained stable in 5 lesions. SUVR (lesion/SSS) was evaluated in 16 lesions. Compared to baseline, SUVR (lesion/SSS) at 6 months was partially reduced (PR, ≥50%) in 2 lesions, minimally reduced (MR, <50% and ≥25%) in 3 lesions, and stable (SD, <25% reduction and <25% increase) in 11 lesions. CONCLUSIONS 68Ga-Dotatate PET is a promising imaging biomarker in patients with advanced meningioma. Treatment with 177Lu-Dotatate led to substantial reduction in SUVR (lesion/SSS) in a subset of patients. In contrast to other reports, 68Ga-Dotatate assessments were generally concordant with post-gad T1 based MRI assessments per RANO. Updated results in an expanded group of patients will be presented.

Abstract BACKGROUND Most meningiomas are considered benign tumors, however, a subset of meningiomas are characterized by a more aggressive clinical course and require multimodal treatment. Beyond surgery and radiation, there are no effective medical treatments available. Somatostatin receptor 2 (SSTR2) is expressed by the majority of meningiomas. [177Lu]Lu-DOTA-TATE (177Lu-Dotatate) is a SSTR2-targeting radioligand therapeutic agent that has been successful in other oncological entities, including neuroendocrine tumors. Here we report the results of a phase 2 clinical trial (NCT03971461) evaluating 177Lu-Dotatate in patients with advanced and treatment-refractory intracranial meningiomas. METHODS In this multicenter, open-label, phase 2 study, adults with advanced intracranial meningiomas received 177Lu-Dotatate at 7.4 GBq (200 mCi) every eight weeks for four doses. [68Ga]Ga-DOTA-TATE (68Ga-Dotatate) PET was performed before and at the end of treatment. 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, and 68Ga-Dotatate uptake on PET. RESULTS Thirty-two patients (F=21, M=11) with progressive meningiomas (WHO 1=7, WHO 2=24, WHO 3=1) were enrolled. Median age was 65.5 (range 41-78) years. All patients previously underwent tumor resection and at least one course of radiation. Three patients (9%) had received medical therapy. Treatment with 177Lu-Dotatate was well tolerated, no treatment-limiting toxicities were observed. Of 29 evaluable patients at the data cutoff, 19 patients (66%) had achieved PFS-6 (WHO 1=4, WHO 2=15). Radiographically, the best response was partial response (PR) in 2 patients (6%) and stable disease (SD) in 20 patients (63%). CONCLUSIONS Treatment with SSTR2-targeting 177Lu-Dotatate is well tolerated and 66% of patients achieved PFS-6, comparing favorably to historical benchmarks, 177Lu-Dotatate therefore may be a useful new therapeutic modality for patients with advanced meningiomas and will be further explored in MOMENTUM-1 (NCT#06955169), an open-label, randomized, phase 2 trial.