Treatment Outcome of Gamma Knife Radiosurgery for Petroclival Meningiomas: Retrospective Analysis of a Single Institution Experience

Abstract

Background: Although Gamma Knife radiosurgery (GKRS) has been widely used for intracranial meningiomas as an alternative or adjuvant treatment, guidelines have not been established for the selection of patients with petroclival meningioma (PCM) for GKRS. In this study, we reported the factors related to tumor progression and postoperative complications in PCM patients treated by GKRS, with a review of the literatures.

Methods: Between 2004 and 2019, 64 patients (52 patients for alternative and 12 patients for adjuvant treatment) with PCM underwent GKRS in our institution. The clinical and radiological factors were retrospectively analyzed. The mean radiologic follow-up duration was 58.4 months (range, 6-164 months). The mean tumor volume and diameter before GKRS were 13.4 cm³ and 2.9 cm, respectively. The median marginal dose was 12 Gy (range, 10-14 Gy) with a 50% median isodose line. Fractionation was used in 19 cases (29%, two fractionations in 5 cases & three fractionations in 14 cases).

Results: Progression was noted in 7 cases (10.9%) and the progression-free survival rates were 91.1% at 5 years and 69.6% at 10 years. Although large in volume, moderate to severe peritumoral edema and male gender were somewhat related to progression, they did not reach statistical significance. Ten patients (15.6%) developed complications after GKRS. The most common complication was cranial nerve deficit (n=8), followed by hemiparesis, cognitive dysfunction, and hydrocephalus. Large size (maximal diameter ≥5 cm) [hazard ratio (HR) 0.091, 95% confidence interval (CI) 0.014-0.608; p=0.013] and multiplicity (HR 0.102, 95% CI 0.018-0.573; p=0.009) were independent factors for developing complications after GKRS.

Conclusion: GKRS can be considered an effective and safe treatment for large-volume PCM. However, for patients with large size or multiple masses, the treatment method should be determined with caution because the probability of complications after GKRS may increase.

Keywords: Bone, petrous; Clivus; Gamma knife radiosurgery; Intracranial meningioma; Postoperative complications; Treatment outcome.

Fig. 1. Kaplan-Meier curves showing the progression-free survival (PFS) and cumulative survival of the enrolled patients in this study (overall comparison was estimated using a log-rank test). The overall 5-year PFS rate was 91.1% and the 10-year PFS was 69.6%.

Fig. 2. Kaplan-Meier curves showing progression-free survival (PFS) according to different predictors (overall comparison was estimated using a log-rank test). The number on the right upper of each curve represents the p-value. A: sex, B: fractionation, C: T2 signal intensity (SI), D: perilesional edema, E: maximal diameter, F: tumor volume.

Fig. 3. Serial gadolinium-enhanced MRIs in a 38-year-old man with diplopia. Fractionated GKRS was performed for the tumor, gradually decreasing in the tumor volume from 48.9 cm³ to 28.9 cm³, without neurological complications. GKRS, Gamma Knife radiosurgery.

Fig. 4. Serial gadolinium-enhanced MRIs for a 58-year-old woman with 6th nerve palsy. Single-session GKRS was performed for the tumor, gradually decreasing in the tumor volume from 48.3 cm³ to 21.7 cm³. There was no neurological aggravation during the follow-up period. GKRS, Gamma Knife radiosurgery.

Fig. 5. Serial gadolinium-enhanced MRIs for an 82-year-old woman with incidentally detected petroclival meningioma. Fractionated GKRS was performed for the tumor. The tumor initially decreased in volume but eventually progressed despite a 2nd GKRS. GKRS, Gamma Knife radiosurgery.