Stereotactic radiosurgery for pancreatic neuroendocrine tumor brain Metastases: Systematic review and Illustrative case presentation

•Systematic review of brain metastases (BM) from neuroendocrine tumors (NETs) highlights their heterogeneity.•Most reported cases are of pulmonary NET BM, with limited data on BM originating from other NETs.•First reported case of stereotactic radiosurgery for pancreatic neuroendocrine tumor BM.•Pancreatic NET BM are exceedingly rare and associated with poor prognosis. Neuroendocrine tumor (NET) brain metastases (BM) are rare malignancies which frequently bear a poor prognosis and have the potential to secrete hormones. The optimal treatment approach for these metastases remains unclear, with significant heterogeneity occurring both across and within primary tumor types, and outcome data are limited. Pancreatic neuroendocrine tumor (pNET) BM may be particularly aggressive. While stereotactic radiosurgery (SRS) for other NET BM has previously been described, no report has specifically investigated SRS for management of pNET BM. A comprehensive literature search was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Search terms included (“neuroendocrine tumor” OR “neuroendocrine neoplasm” OR “neuroendocrine carcinoma” OR “NET”) AND (“brain metastasis” OR “brain metastases” OR “intracranial metastases”) AND (“stereotactic radiosurgery” OR “stereotactic body” OR “CyberKnife” OR “GammaKnife”). Our search strategy yielded 230 articles. After screening, a total of 16 articles with 256 patients were identified. Number of patients per study cohort ranged from 1 to 101 (mean = 16). Ten articles were single case reports. The most commonly investigated primary site was lung (5 studies), followed by skin (2 case reports), and uterine cervix (2 case reports). Median survival post-SRS ranged from 5 to 42 months. Median tumor volume ranged from 0.08 cm3 to 33.62 cm3. Local control rate was provided in 3 of 6 of the reviewed retrospective analyses. A pulmonary cohort of 101 patients reported a recurrence rate of 13.8 % at 12 months. A pulmonary case series similarly reported local progression in only 1 of 8 patients. The mixed primary cohort (33 patients) had a long-term local failure rate of 16.7 %. In addition, we describe a first reported individual case of pNET BM treated with SRS. Nearly 6-years after initial pNET diagnosis, multiple intracranial enhancing lesions were found, which were subsequently treated with SRS. Follow-up imaging demonstrated a statistically significant decrease in lesion diameter (p