Stereotactic radiosurgery for pineal gland metastases: results from the international radiosurgery research foundation

Purpose: Metastases to the pineal gland are rare. Surgical excision can be associated with high rates of morbidity. Alternatively, stereotactic radiosurgery (SRS) for brain metastases in the pineal region has not been vigorously studied. Methods: We performed a multi-institutional retrospective study for patients treated with SRS for pineal region metastases at treatment centers that comprise the International Radiosurgery Research Foundation (IRRF). Demographics, tumor characteristics, treatment parameters, and clinical outcomes were collected. The primary endpoint was local tumor control (LC). Secondary endpoints included: Overall survival (OS), distant tumor control (DC), and adverse radiation events (AREs). Kaplan-Meier and Cox regression analyses were performed to evaluate time to event endpoints and prognostic factors respectively. Results: Twenty-six patients (16 female, 62% median age 60 years (range: 16–87) with 26 pineal metastases were managed with SRS. Primary tumor histology was lung (46.2%), breast (26.9%), melanoma (7.7%), and other (19.2%). SRS treatment was up-front in the majority of cases (61.5%), adjuvant (19.2%) or salvage therapy (19.2%). The median prescription dose was 18 Gy in a single fraction. Median follow-up was 9 months (range 3–101). LC at 3-,6-,12-, and 24-months was 100%, 94.4%, 87.7%, and 87.7% respectively. DC at the same intervals were 79.2%, 73.9%, 52.8%, and 35.2%. Median OS was 32 months (range: 6–52). No evaluated prognostic factors were significantly associated with LC, DC, or OS. Among the 13 patients with symptoms related to their pineal tumor at baseline, 7 improved and 6 remained stable following SRS. Leptomeningeal spread occurred in 7.7% of patients and no cases of post-SRS hydrocephalus were observed. Overall AREs occurred in 14 (53.8%) patients, with a median time to onset of 4 months. Conclusion: SRS offers excellent local tumor control of pineal metastases with high rates of symptomatic improvement, minimal leptomeningeal spread, and limited post-SRS complications. Despite this, distant tumor control is limited in this setting and may be improved by improved systemic disease management.