IMG-72. [68Ga]Ga-DOTA-TATE PET as imaging biomarker for response assessment and monitoring in patients receiving [177Lu]Lu-DOTA-TATE for advanced intracranial meningioma

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.