The rate of vertebral compression fracture (VCF) is determined by the number of participants who develop VCF possibly, probably, or definitely related to the protocol therapy, as opposed to tumor progression. This is assessed and determined by the treating physician by reviewing the initial MRI done prior to starting protocol therapy compared to MRI scans done at follow up visits after receiving protocol therapy.

The number of treatment-related adverse events during the study will be assessed by the NCI Common Terminology Criteria for Adverse Events (CTCAE) version 5 within 3 months of completing the protocol therapy that are determined to be grades 2 or higher (acute toxicity) by the treating physician.

The local control (LC) is defined as the absence of progression of the disease at the treated spinal area. The LC rate is assessed by comparing two separate MRI scans - the initial MRI done prior to starting therapy compared to the MRI done one month after completing protocol therapy. The rate is determined by assessing progression of disease between the two MRI scans.

The local progression (LP) is defined as the unequivocal increase in tumor volume or linear dimension, any new or progressive tumor within the treated area; or neurological deterioration attributable to pre-existing epidural disease with equivocal increased epidural disease dimensions. The LP rate is assessed by comparing two separate MRI scans - the initial MRI done prior to starting therapy compared to the MRI done one month after completing protocol therapy.

The mean relative epidural tumor reduction measures the tumor size assessed on the initial MRI scan done prior to starting protocol therapy compared to the tumor size assessed on MRI scan done one month after completing protocol therapy.

The overall epidural tumor response rate is determined by the objective response rate (ORR) which is defined by the number of participants with objective response to protocol therapy compared to overall number of study participants. This rate is determined based on review of two MRI scans - the initial MRI scan done prior to starting protocol therapy compared to the MRI scan done one month after completing protocol therapy.

The change in mean relative thecal sac patency is defined as [(postradiosurgery thecal sac area minus preradiosurgery thecal sac area) divided by pre radiosurgery thecal sac area].

The change in thecal sac decompression rate is defined as the number of study participants who experienced a relative improvement of thecal sac patency at 1 month post-radiotherapy (post-RT) MRI divided by the total number of study participants.

The in-field progression (IFP) rate is defined as the proportion of patients with in-field progression, where IFP is defined as the increase in tumor size, any new or progressive tumor within the treatment area, or neurological deterioration attributable to preexisting disease in treatment area. This is determined based on review of two MRI scans - the initial MRI scan done prior to starting protocol therapy compared to the MRI done one month after completing protocol therapy.

The distant progression (DP) rate is defined as the proportion of patients who experience DP, where DP is defined as the increase in tumor size or any new or progressive tumor outside of the treatment area.

The failure-free survival (FFS) is defined as the time from study enrollment to the first documented clinical failure or death from any cause, whichever occurs first.

The overall survival (OS) is defined as the time from study enrollment to the time of first documented death from any cause.

The EQ-5D-5L represents a global quality of life measure that includes multiple components. The EQ-5D-5L score includes questions on mobility, self-care, usual activities, anxiety/depression, and pain/discomfort on a 5-point scale: 1=No Problem, 2=Slight Problem, 3=Moderate Problem, 4=Severe Problem, 5=Extreme Problem or Inability. 0, 1, and negative values correspond to death, full health, and health states worse than death, respectively. Higher scores indicate greater levels of problems across each of the five dimensions.

Defined by the Functional Assessment of Cancer Therapy General (FACT-G), a 27-item questionnaire designed to measure four domains of health-related QOL in cancer participants. Items are rated on a 5-item Likert scale. Scores range from 0-108. Higher scores indicate better quality of life.

The BPI measures pain intensity and the functional interference caused by pain via four items assessing average, worse, least, and immediate pain intensity in the last 24 hours. Pain intensity is measured using an 11-point numeric rating scale (0=no pain; 10=worst you can imagine). Higher scores indicate greater pain.

The ambulation status is evaluated on a 4 level scale where normal = 0, walking with 1 cane = 1, walking with a walker frame = 2, and walking not possible = 3. Scores of 3 at interval follow-up indicate loss of independent ambulation. The rate of preservation is the proportion of patients with preservation divided by the total number of patients on study. Preservation is determined by comparing baseline ambulatory score to interval follow up score.

The planning target volume (PTV) maximum dose (Dmax) is the max dose that is planned for study participants to receive. PTV Dmax will be measured in cubic centimeters.

The PTV Dose mean (DMean) is the average dose planned to received by participants. PTV DMean will be measured in grays (Gy).

PTV D80 is the dose received by 80% of the targeted area. This is recorded for initial and subsequent radiotherapy plans to verify the advantages of planning and modifying dose levels as needed. PTV D80 will be measured in grays (Gy).

PTV D95 is the dose received by 95% of the treated area. This is recorded for initial and subsequent radiotherapy plans to verify the advantages of planning and modifying dose levels as needed. PTV D95 will be measured in grays (Gy).

The spinal cord maximum dose is recorded for initial and subsequent radiotherapy plans to verify the advantages of planning and modifying dose levels as needed. Spinal cord Dmax will be measured in cubic centimeters.

The spinal cord (SC) D0.03 is recorded for initial and subsequent radiotherapy plans to verify the advantages of planning and modifying dose levels as needed. D0.03 is measured in cubic centimeters.

The spinal cord (SC) D0.1 is recorded for initial and subsequent radiotherapy plans to verify the advantages of planning and modifying dose levels as needed. D0.1 is measured in cubic centimeters.

The spinal cord (SC) D1 is recorded for initial and subsequent radiotherapy plans to verify the advantages of planning and modifying dose levels as needed. D1 is measured in cubic centimeters.

The spinal cord D50% is the half maximal inhibitory dose recorded for initial and subsequent radiotherapy plans to verify the advantages of planning and modifying dose levels as needed. D50% is measured in grays (Gy).

The area under the curve (AUC) is used for receiving operating characteristic analysis to build models predictive of clinical outcomes, incorporating baseline demographics, clinical and laboratory data and radionics features. The target AUC is greater than or equal to 0.80.

Dice's coefficient is use to train machine learning algorithm using MRIdian images to automatically segment tumor, spinal cord, and normal structures in order to improve workflow efficiency of MRI-linac adaptive planning for treatment of protocol disease. The target coefficient is greater than or equal to 0.80.