Stereotactic Body Radiation Therapy (SBRT)
Overview
Stereotactic body radiation therapy (SBRT) is an image-guided, conformal radiation technique that delivers high doses of radiation to an extracranial target in 1–5 fractions, using tight margins and rigorous patient immobilisation. In oncology it is used for locally advanced or oligometastatic disease where high doses per fraction are tolerable and local tumour control is the goal. Key technical components include 4D-CT simulation for motion management, fiducial-guided tracking, cone-beam CT (CBCT) image guidance (IGRT), and IMRT/VMAT planning. Delivery platforms include linac-based SBRT, CyberKnife, and proton beam systems.
Used by
- Synthesized across nine prospective trials in locally advanced pancreatic adenocarcinoma (PAAD); the multi-fraction reference regimen (33 Gy / 5 fx, Herman et al.) achieved 79% 1-year local control and 13.9-month median OS with 2% acute and 6% late grade 3+ GI toxicity when combined with gemcitabine. Single-fraction regimens (15–25 Gy) achieved 100% local control but universal distant progression. PMID:27826200
Notes
- Current reference regimen for unresectable locally advanced PAAD: 33 Gy in 5 fractions with sequential gemcitabine (Herman et al. multi-institutional trial, n=49).
- Duodenal dose constraints are essential to limit late GI toxicity: V15Gy <9 cc, V20Gy <3 cc, V33Gy <1 cc.
- Single-fraction SBRT (25 Gy) achieves 100% local control but all patients progress distantly, indicating systemic control is the dominant survival determinant.
- Borderline-resectable pancreatic cancer: neoadjuvant SBRT can achieve 84–96% R0 resection rates in patients who proceed to surgery.
- SMAD4/DPC4 status is under investigation as a stratification biomarker to select patients for local intensification vs systemic therapy escalation.
- No prospective randomised comparison vs conventionally fractionated chemoradiation existed as of 2016.
Sources
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