PET with somatostatin receptor ligand [Ga]Ga-DOTA-D-Phe-Tyr-octreotide ([Ga]Ga-DOTA-TOC) is an established method in radiotherapy planning because of the improved detection and delineation of meningioma tissue. We investigated the diagnostic accuracy of supplementary [Ga]Ga-DOTA-TOC PET in patients with a 3-month postoperative MRI reporting gross-total resection (GTR).

Thirty-seven patients with a histologically proven meningioma and GTR on postoperative MRI were prospectively referred to [Ga]Ga-DOTA-TOC PET. Detection and volume measurements of [Ga]Ga-DOTA-TOC-avid lesions in relation to the primary tumor site were recorded. Residual tumor in suspicious lesions suggested by [Ga]Ga-DOTA-TOC PET was verified by (i) tumor recurrence/progression on subsequent MRI scans according to the Response Assessment of Neuro-Oncology criteria, (ii) subsequent histology, and (iii) follow-up [Ga]Ga-DOTA-TOC PET scan.

Twenty-three PET scans demonstrated [Ga]Ga-DOTA-TOC-avid lesions suspicious of residual meningioma, where 18 could be verified by (i) tumor progression on subsequent MRI scans ( = 6), (ii) histologic confirmation ( = 3), and (iii) follow-up [Ga]Ga-DOTA-TOC PET scans confirming the initial PET findings ( = 9) after an overall median follow-up time of 17 months (range, 9-35 months). In contrast, disease recurrence was seen in only 2 of 14 patients without [Ga]Ga-DOTA-TOC-avid lesions ( < 0.0001). The sensitivity, specificity, and diagnostic accuracy of [Ga]Ga-DOTA-TOC PET in detecting meningioma residue was 90% [95% confidence interval (CI), 67-99], 92% (95% CI, 62-100), and 90% (95% CI, 74-98; < 0.0001), respectively.

The majority of patients with GTR on 3-month postoperative MRI may have small unrecognized meningioma residues that can be detected using [Ga]Ga-DOTA-TOC PET.