Study of Combined Decompressive Spine Radiosurgery and Pembrolizumab

Inclusion Criteria : * Pathologic diagnosis of cancer, confirmed by review of pathology report. * Epidural disease seen on MRI at 1 vertebral level or 2 contiguous vertebral level. * Synchronous and metachronous sites of disease allowed. * Patient with expected life span of ≥ 3 months. * Deemed eligible for stereotactic body radiation therapy and pembrolizumab after multi-disciplinary review. The multi-disciplinary review will be conducted virtually via our Spinal Oncology Group (SPOG) Wake Forest e-mail listserv. Members of the distribution list include neurosurgeons, orthopedic surgeons, interventional radiologists, radiologists, and radiation oncologists. This group meets monthly via Webex and in the interim, cases are routinely reviewed using encrypted emails via the listserv. Because we will not be able to wait for a month meeting to enroll patients on study, we anticipate needing to review these patients via the listserv. The electronic review will serve as documentation of multi-disciplinary review. * Patients currently being treated with pembrolizumab or anticipated to receive at least one dose of pembrolizumab within six weeks after finishing stereotactic body radiation therapy. * Patients who have received prior immunotherapy are allowed. * Age equal or greater than 18. * Ability to understand and the willingness to sign an IRB-approved informed consent document (either directly or via a legally authorized representative). Exclusion Criteria: * Prior radiation therapy or surgery to index lesion. * Patients with lymphoma, multiple myeloma, germinomas, seminomas, Wilm's tumors, and Ewing's sarcomas will be excluded. * Muscle strength of ≤ 3 out of 5 on neurologic exam that correlates with level of the involved spinal cord. * Retropulsed compression fracture. * Patients with a contraindication to pembrolizumab. * Patients may not be receiving any other investigational agents. * Patients with symptomatic, brain metastases, as determined by the study PI, that could confound the neurologic exam, should be excluded. * Uncontrolled intercurrent illness including, but not limited to ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements. * Pregnant women are excluded from this study because both radiation and pembrolizumab can be harmful to the developing fetus. Because there is an unknown but potential risk for adverse events, pregnant women are not allowed to participate in this study, in nursing infants secondary to treatment of the mother with pembrolizumab, breastfeeding should be discontinued.