Gamma Knife Radiosurgery as a Primary Treatment for Nonfunctioning Pituitary Adenoma Invading the Cavernous Sinus

Surgical resection of nonfunctioning pituitary adenoma (NFPA) invading the cavernous sinus (CS) remains a challenging and significant factor associated with incomplete resection. The residual tumor in CS is usually treated with adjuvant stereotactic radiosurgery (SRS), but there is little information concerning SRS as an initial treatment for CS-invading NFPA. In this study, we investigated the tumor control rate and clinical outcomes of the patients who received primary gamma knife radiosurgery (GKRS) for CS-invading NFPA.

This was a single-institute retrospective analysis of 11 patients. CS invasion of tumor was categorized using the modified Knosp grading system. The median tumor volume and maximal diameter were 1.6 cm3 (range 0.4-6.5) and 17.2 mm (range 11.6-23.3), respectively. The median clinical follow-up period was 48.5 months (range 16.4-177.8). The median prescription dose at tumor margin was 15 Gy (range 11-25) and median prescription isodose was 50% (range 45-50). The maximum radiation dose to optic chiasm and optic nerve were 7.2 Gy (range 3.4-9.2) and 7.5 Gy (range 4.5-11.5), respectively.

Tumor control was achieved in all patients. The median tumor volume and maximal diameter at last follow-up were 0.4 cm3 (range 0.1-2.3) and 11.4 mm (range 4.7-19.5), respectively. The median volume reduction rate was 52% (range 33-88). Six patients showed downgrading of modified Knosp grade after GKRS. No patients developed GKRS-related complications such as hypopituitarism or visual disturbance.

SRS may be an alternative primary treatment option for CS-invading NFPA if there is no urgent and absolute indication for surgery such as optic apparatus compression.