The goal of this clinical trial is to learn if a higher dose of Stereotactic Spine Radiosurgery (SSRS), an advanced radiation technique, is better for treating cancer that has spread to the spine (spinal metastases). The study will also learn about the safety of using a higher dose.

The main questions it aims to answer are:

Does a higher radiation dose lead to fewer treatment failures (meaning the tumor growing back or causing serious side effects) one year after treatment? What are the side effects associated with the high dose compared to the standard dose? How does each radiation dose affect a patient's pain and quality of life?

Researchers will randomly assign participants (like a coin toss) to one of two groups to compare the outcomes:

The Standard Dose Group: Will receive a single radiation treatment of 16 Gy. The High Dose Group: Will receive a single, more powerful radiation treatment of 20 Gy.

Participants in this study will:

Receive a single, one-time, highly-focused radiation treatment (SSRS) to the spinal tumor.

Attend regular follow-up visits at the clinic for checkups and imaging scans (like MRI).

Complete questionnaires about their pain levels and quality of life during these visits.

Study Rationale and Background:

Metastatic cancer to the spine is a significant clinical challenge that can lead to severe pain, neurological compromise, and a diminished quality of life. Stereotactic Spine Radiosurgery (SSRS), also known as Stereotactic Ablative Radiotherapy (SABR), has emerged as a paradigm-shifting treatment. This advanced, non-invasive technique allows for the delivery of a single, highly ablative dose of radiation with unprecedented precision, which has shown excellent rates of pain control and tumor response while minimizing dose to the adjacent, critical spinal cord.

Despite the widespread adoption and promising results of SSRS, the optimal dose-fractionation schedule remains an area of active investigation. Previous research, including the landmark RTOG 0631 trial, has established single-fraction 16 Gy as an effective regimen. However, other evidence suggests that a higher radiation dose may lead to more durable local tumor control. This prospective, randomized phase II study, known as the SHINE trial, is designed to formally compare the efficacy and safety of a higher single-fraction dose against the current standard dose.

Study Design and Procedures:

This is a two-arm, parallel-group, randomized, open-label, multi-center study. After providing informed consent and confirming eligibility, participants will be randomly assigned on a 1:1 basis to receive either the standard dose or the high dose of SSRS. The randomization process will incorporate a minimization procedure to ensure balance between the two arms for the key prognostic factor of epidural or paraspinal tumor extension.

The core intervention for all participants is a single session of SSRS. The treatment will be meticulously planned using fused CT and MRI scans to accurately delineate the tumor (Gross Tumor Volume, GTV) and the area at potential microscopic risk (Clinical Target Volume, CTV), following international consensus guidelines from the International Spine Radiosurgery Consortium (ISRC). Radiation will be delivered using state-of-the-art techniques (IMRT or VMAT/RapidArc) with rigorous on-board image guidance to ensure accuracy. Strict dose constraints will be applied to protect the spinal cord and other nearby organs at risk.

Follow-up and Data Collection:

Following treatment, all participants will enter a comprehensive follow-up phase lasting up to two years. The schedule includes regular clinical evaluations, neurological assessments, and serial imaging (MRI and/or CT) to monitor treatment response and detect any potential late toxicities. Additionally, participants will complete validated questionnaires to assess changes in pain and health-related quality of life. Blood samples will be collected at baseline for correlative science studies to investigate potential genetic biomarkers (such as DDR2) and circulating factors that may predict treatment response or risk of skeletal side effects. This robust data collection will allow for a thorough comparison of the two treatment regimens.

Inclusion Criteria:

1. Patients with a histologic diagnosis of non-hematopoietic malignancy
2. Radiographic evidence of localized spine metastases without leptomeningeal involvement or intramedullary lesion
3. Maximum four separate sites with a maximal involvement of two continuous vertebral levels
4. Patients do not have prior radiotherapy to the index spine(s)
5. Age ≥ 18 years
6. Karnofsky performance status (KPS) ≥ 60%.
7. Life expectancy ≥ 12 months.
8. Women of childbearing potential and male participants must practice adequate contraception
9. Patients must be able to comply with the study protocol and follow-up schedules and provide study-specific informed consent

Exclusion Criteria:

1. Prior radiotherapy or radiosurgery to the index spine(s)

2. Serum creatinine > 2.0 mg/dL within 90 days prior registration

3. Contraindication to MR imaging such as implanted metal devices or foreign bodies, severe claustrophobia

4. Patients with metastatict epidural spinal cord compression (≥ grade 2) at the index spine(s) indicative of upfront spine surgery

5. Inability to tolerate treatment procedure

6. Severe, active comorbidities which, in the judgment of the investigator, would make the patient inappropriate for entry into this study or interfere significantly with the proper assessment of safety and adverse events of the protocol, or limit compliance with study requirements, defined as follows:

   1. Uncontrolled active infection requiring intravenous antibiotics at the time of registration
   2. Transmural myocardial infarction ≤ 6 months prior to registration
   3. Unstable angina or congestive heart failure requiring hospitalization ≤ 6 months prior to registration
   4. Life-threatening uncontrolled clinically significant cardiac arrhythmias
   5. Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects
   6. Chronic obstructive pulmonary disease exacerbation or other respiratory illness requiring hospitalization or precluding study therapy at the time of registration
   7. Uncontrolled psychiatric disorder

7. Will receive any other investigational agent or chemotherapy and/or target therapies during treatment

8. Women of childbearing potential and male participants who are sexually active and not willing/able to use medically acceptable forms of contraception; this exclusion is necessary because the radiation treatment involved in this study may be significantly teratogenic

9. Pregnant or breast-feeding women