Application of a New Protocol for Extent of Resection of Meningiomas

Background: Patients with meningiomas are at high risk of tumor progression and recurrence regardless of initial management. After surgery, up to 50% of meningiomas regrow and recurrences as well as living with a chronic disease affect disease-specific survival and health negatively. One obstacle to optimal disease management is poor knowledge of which patients may be cured by initial surgery and hence at no risk of recurrence; a traceable definition and operationalization of complete removal is needed. We have proposed a novel grading of extent of resection as a means to identify patients with bona fide complete removal of a meningioma.

Methods: We have prospectively attempted to describe all patients operated for meningiomas according to the protocol since April 1, 2021. At surgery, four biopsies are obtained from resection margins and additionally from tissue where uncertainty prevails. These are analyzed microscopically after histological and immunohistochemical staining. At 3 to 6 months after surgery, regular MRI scanning is supplemented with Dotatoc-PET to identify tissue with Somatostatin type 2 receptor (SST2R) expression. The protocol next assigns 0 for negative and 1 for positive margins (0 or 1/×) and 0 or 1 for the presence of tumor suspicious tissue with the expression of SST2R (×/0 or 1) for a combined score of 0/1, 1/0, 0/1, or 1/1.

Results: Of 418 patients operated until December 31, 2023, a total of 264 patients were enrolled in the protocol.

Dotatoc PET at follow-up was available from 212 consecutive patients. Three were omitted in cases of logistical difficulties and the rest had not yet been scanned. Of 212 patients, 168 patients had residual tumor after resection at 3 months of follow-up. In 33% (55/168) of the cases, DOTATOC-PET showed residual tumor where MRI was uncertain. In 28% (47/168) of the cases, DOTATOC-PET showed residual tumor not seen on MRI.

Biopsies were obtained from 90 patients; failure to obtain biopsies occurred because it was considered futile as macroscopic tumor was left, technical difficulties or oversight. Twenty patients were negative in biopsies and scanning, 13 were positive in biopsies and negative in scanning, 15 were negative in biopsies and positive in scanning, 23 were positive in biopsies and scanning.

Conclusion: The combination of microscopic evaluation of resection margins and Dotatoc-PET scanning provided a feasible definition and operationalization of extent of resection with better potential reproducibility and traceability than previous definitions, although logistics provided a challenges precluding complete inclusion. Dotatoc-PET and histopathology were complementary since 13 (14%) or 15/90 (17%) patients with residual tumor were detectable only with one method and 23 were detectable with both (26%). Complete removal was unexpectedly rare in this cohort of meningioma patients.

 

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No conflict of interest has been declared by the author(s).

Publication History

Article published online:
07 February 2025