SBRTSRS

SBRTSRS is a term used to describe an integrated approach to applying stereotactic radiotherapy techniques to both intracranial and extracranial targets, combining elements of stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS). Proponents view SBRTSRS as a unified framework that emphasizes precise, image-guided dose delivery in a small number of treatment fractions regardless of target location, enabled by advances in immobilization, image guidance, and motion management.

In practice, the distinction between brain-focused SRS and body-focused SBRT is narrowing under this concept, with similar planning and delivery workflows, dose constraints, and evaluation of local control and toxicity.

Techniques involve immobilization with frameless or frame-based systems, CT/MRI fusion for target delineation, meticulous treatment planning to minimize dose to normal tissue, and image-guided radiotherapy delivery on modern linear accelerators.

Indications include oligometastatic disease, small primary tumors, and select benign or malignant lesions amenable to ablative doses, with applications described for brain metastases, spinal metastases, and lung, liver, pancreas, and kidney lesions.

Dosing regimens vary; head targets may receive single-fraction SRS (for small lesions) or hypofractionated schedules, while extracranial SBRT commonly uses 3-5 fractions totaling 24-60 Gy depending on site and tolerance. Risks include radiation necrosis, edema, fatigue, and organ-specific toxicity; careful patient selection and QA are essential.

Status and terminology: SBRTSRS is an emerging concept and not universally standardized; most evidence remains separate for SBRT and SRS, with ongoing research aimed at harmonizing protocols and assessing comparative outcomes.