Response assessment of somatostatin receptor targeted radioligand therapies for progressive intracranial meningioma.

Background:  In somatostatin receptor (SSTR) expressing progressive meningioma, peptide receptor radionuclide therapy (PRRT) has shown effect in small clinical series. However, standardized treatment and response assessment protocols are lacking. We present our experience on PPRT with Lu-DOTATATE in progressive meningioma with a special emphasis on state-of-the-art response assessment.

Methods:  Retrospective analysis on PRRT with Lu-DOTATATE from 2015 to 2019. Pre- and post-therapy imaging was performed using MRI and Ga-DOTATATE-PET for standard bidimensional and volumetric analyses, respectively, following novel RANO guidelines.

Results:  Seven patients with progressive intracranial meningioma (median age 73 years, interquartile range 60-76; 5 WHO II, 2 WHO I; 5 multifocal) received a median of 4 cycles 2 3 4 of PRRT with Lu-DOTATATE in eight-week intervals. Three patients did not undergo post-therapy Ga-DOTATATE-PET due to early symptomatic progression and subsequent cessation of PRRT. After completion of 4 PRRT cycles volumetric PET imaging showed stable disease in two of four patients. According to bidimensional MRI response assessment, only one patient was stable. Progression free survival at six months was 42.9 %.

Conclusion:  In this heterogeneous collective of seven patients with progressive meningioma, 177Lu-DOTATATE therapies showed heterogeneous effectiveness. PET-based volumetric assessment should be used for response assessment in PRRT additionally to bidimensional imaging.