Inclusion Criteria:  Age > 18 years old. (The indication for this technique is controversial in skeletally immature patients.) Histologic diagnosis of solid malignant tumor (not one of the more radiosensitive histologic subtypes, see Exclusion Criteria), including but not limited to non-small cell lung cancer, breast, prostate, renal cell, melanoma, gastrointestinal, sarcoma, thyroid, head and neck primary, and unknown primary tumors. Quantification of the degree of epidural spinal cord compression as grade 1C, 2, or 3 by MRI, with and without contrast sequences. Axial T2 sequence is encouraged but not required. The vertebral body site to be treated must be located from T2 to L1 No more than 3 contiguous or dis-contiguous vertebral levels involved with metastasis in the spine to be irradiated in a single session or 3 sessions. Motor strength ≥4 out of 5 in extremity or extremities affected by the level of the spinal cord compression (see section 4 for grading method). ECOG performance status <2 or Karnofsky performance status (KPS) >50 Life expectancy >3 months. Inoperable disease because of patient refusal, neurosurgical evaluation, or any other medical reasons. Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) before study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she should inform her treating physician immediately. Prior conventional radiation to the same site is allowed as long as there is a greater than 3 months interval. Signed informed consent.  Exclusion Criteria:  Requires open spinal procedure or a percutaneous procedure without the use of image guidance. Primary tumors of radiosensitive histology (lymphoma, multiple myeloma, small cell carcinoma, germ cell tumors), as conventional radiation is likely to be effective in such cases. Unable to tolerate general anesthesia and prone position. Unable to undergo MRI scan of the spine. Inability to lie flat on a treatment table for >60 minutes. Pregnant. (Urine testing must be done no more than 10 days prior to surgery.) Prior conventional irradiation of the spine site and level to be treated with an interval shorter than 3 months. Frank cord compression or cord compression from bone components or configuration and acute neurological deficits (defined as motor strength <4/5 in extremity or extremities affected by the level of the spinal cord compression)