• ACR-ARS Practice Parameter for the Performance of Stereotactic Body Radiation Therapy
• Sacral fracture risk after stereotactic spinal radiosurgery: a multi-institution, retrospective analysis
• Long term outcomes following upfront stereotactic body radiotherapy alone for spinal metastases
• Histological Classifier of Radiosensitivity to Spine Stereotactic Body Radiation Therapy
• Local Control and Toxicity Outcomes After Stereotactic Body Radiation Therapy for Metastatic Osteosarcoma in Pediatric Patients
• Comprehensive end-to-end dosimetry audit for stereotactic body radiotherapy in spine, lung, and soft tissue
• Evaluation of the Accuracy of Patent Fixation System Using a Bi-directional X-ray Image Matching System during Spine Stereotactic Body Radiation Therapy
• Same-Day Magnetic Resonance-Guided Single-Fraction Stereotactic Body Radiation Therapy for Painful Non-Spine Bone Metastases - A Single-Center Study ("BONE SHOT")

Also known as stereotactic ablative radiotherapy (SABR) when referring to high-dose, image-guided treatment of spinal tumors.

Definition: Spine SBRT is a high-precision form of external beam radiation therapy that delivers high doses of radiation to spinal metastases or primary tumors in 1 to 5 fractions, using advanced image guidance and immobilization techniques.

It is designed to:

• Maximize tumor control (local control rates >80%)
• Spare the spinal cord and surrounding healthy tissues
• Minimize treatment time and patient burden

Key features:

• Submillimeter precision with image-guided radiation delivery
• Dose escalation without increasing toxicity
• Often used as an alternative to surgery or after separation surgery

Indications:

• Oligometastatic spinal disease
• Radioresistant tumors (e.g., RCC, melanoma)
• Re-irradiation of previously treated spine levels
• Pain control and spinal cord compression management

Contraindications:

• Severe spinal instability without surgical stabilization
• Extensive epidural compression (ESCC 3) unless surgery is performed first

SBRT requires detailed planning, including MRI/CT fusion, spinal cord contouring, and strict dose constraints.

In a Retrospective Cohort Study Jackson et al. ¹⁾ from the Memorial Sloan Kettering Cancer Center, New York, concluded that 30 Gy in 3 fractions is the preferred SBRT regimen for spinal metastases, even in radiosensitive tumors, because it offers better local control than 27 Gy with a similar risk of vertebral fracture requiring treatment.

Additionally:

Tumor histology strongly influences radiosensitivity — prostate and breast (Class A) respond best; GI and liver tumors (Class C) have higher failure rates.

For high-grade epidural compression (ESCC 2–3) in Class B–C tumors, separation surgery + SBRT may improve outcomes over SBRT alone.

* The study assigns biological significance to histology classes (A–C) without molecular stratification or genomic profiling — a gross simplification that ignores intratumoral heterogeneity and microenvironmental factors. * Retrospective design with non-randomized treatment allocation allows substantial selection bias (e.g., healthier patients might be more likely to receive 30 Gy). * No formal validation cohort — the classifier is proposed based on internal data, without prospective or external validation.

* “Histological classifier of radiosensitivity” suggests a predictive tool, yet the study lacks any predictive modeling or decision support framework. The term is more rhetorical than scientific. * The study mixes observational epidemiology with causal language, implying therapeutic superiority without proper adjustment for confounders.

* Treatment practices evolved over the 9-year window. Earlier patients may have been treated with less advanced planning, different immobilization, or different imaging standards — contaminating outcome comparisons.

* No adjustment for institutional learning curve, planning margins, spinal cord tolerance constraints, or radiologist/radiation oncologist variability. * The impact of systemic therapy (e.g., concurrent immunotherapy, targeted therapy) is not accounted for — a major omission in modern oncologic outcomes.

* Vertebral Compression Fracture rates are reported, but the distinction between radiologic and clinically significant fractures is vague. Moreover, attributing cause solely to dose without biomechanical modeling is speculative. * The apparent increase in overall VCF with 30 Gy, though dismissed as statistically irrelevant, raises safety concerns insufficiently explored.

* The “benefit” of separation surgery in Epidural Spinal Cord Compression (ESCC) 2–3 lesions is statistically non-significant (p = 0.051) and based on a small subgroup (n=261) — yet it is discussed as if near-clinical truth.

This study sells the illusion of a refined, histology-based SBRT dosing paradigm, but offers little more than retrospective rebranding of known practice patterns. It overpromises biological insight while underdelivering methodological rigor.

Until prospectively validated, the so-called “histological classifier” remains an observational artifact, not a clinical decision tool.

* Treat this study as exploratory, not directive. * Avoid reshaping clinical protocols solely based on its conclusions. * Demand prospective validation with molecular data and standardized planning before adopting these thresholds.