Gamma knife radiosurgery as primary treatment for pineal tumors. Clinical, radiological, and survival evaluation with targeted analysis of prognostic factors in a single-center original series

Background: Pineal region tumors (PTs) are a heterogeneous group of lesions whose management strategy remains controversial. Available data highlight the importance of the initial presumptive diagnosis for a therapeutic strategy which may comprise surgery for intrinsic lesions and chemo/radiotherapy for germ cell tumors. Surgical treatment, however, has been traditionally burdened by the extremely high rates of neurological de cits and perioperative mortality, thus Gamma Knife radiosurgery (GKRS) has gained popularity as an effective alter- native in treating PTs. To date, given the rarity of the disease, literature reports on the topic are limited to small clinical series and single case reports. Only about 200 cases of primary GKRS treatments have been reported to date. Methods: This is a single-center retrospective analysis of 12 patients receiving primary GKSR for pineal tumor region tumors. Patients were excluded if gross total or subtotal resection was attempted. The diagnosis was presumed based on neuroimaging and biological markers. Only biopsy (n¼1) and CSF shunting (n¼8) interventions were allowed. Included lesions were meningioma (n¼1), low-grade glioma (n¼1), germ-cell tumor (n¼1), intrinsic pineal low-grade (n¼3), or unclear (n¼6). The mean lesional volume was 5.2 4 cc, mean mar- ginal dose (50% isodose) was 15 2.2 Gy. Results: At a median 30mo follow-up, local control was achieved in 74.9% of cases with a sustained reduction in tumor volume (5.2 4 to 3.4 4.1 cc; p¼0.07). Three patients showed progression (25%) with a median time of 32.6 months and died. The median OS was 53.5 months. Clinical stability/improve- ment was recorded in 60% of patients. Seven patients experienced TRICs, among which 33.3% presented symptomatic radionecrosis (RN) with only transient symptoms. Clinical improvement was associated with lower doses to the brain- stem (p¼0.08), while the onset of new symptoms was associated with the amount of thalamic edema (p¼0.01) as well as the degree of dose decay (p¼0.03). Cystic degeneration was related to lower doses (p¼0.04). Conclusions: These encouraging results support the growing role of GKSR as a primary treatment for pineal region tumors, demonstrating the need for further studies aimed at validating its ef cacy and safety.