Dose Constraints for Organs at Risk in Abdominal SBRT

Gastrointestinal Organs at Risk

For anal cancer, intensity-modulated techniques with strict dose constraints to bowel are recommended, though specific SBRT constraints for rectal tumors are not well-established in the provided evidence 1

Mean liver dose should be kept at 15-20 Gy depending on baseline liver function, with stricter constraints for compromised hepatic reserve 2, 3
Child-Pugh A patients represent the safest population for liver SBRT, with most safety and efficacy data available for this group 2, 3
Child-Pugh C cirrhosis is an absolute contraindication to SBRT, as safety has not been established in this population with very poor prognosis 2, 3

Maximum spinal cord dose should be limited to 20 Gy in 3 fractions or 13 Gy in a single fraction to maintain myelopathy risk below 1% 4, 5

Mean esophageal dose should be kept below 28 Gy to maintain grade 3+ esophagitis risk below 15% in conventional fractionation 4

Dose to chest wall should be limited to <30 Gy delivered in 3-5 fractions on a volume <30 mL 4
Risk of rib fractures is approximately 5% when dose to 2 mL volume is limited to 27 Gy in 3 fractions (3 × 9 Gy) 4

Renal cell carcinoma metastases show excellent 2-year local control rates of 90% with SBRT, suggesting kidneys can tolerate ablative doses when appropriately planned 3, 5

Hydrodissection techniques can enable safe treatment of lesions abutting critical structures including diaphragm 2

Never use conventional low-dose palliative radiation (8 Gy in 1 fraction) for abdominal tumors in patients with reasonable life expectancy, as this achieves suboptimal local control rates below 50% at 1 year for bulky tumors 3, 5
Avoid treating patients with Child-Pugh C cirrhosis with liver SBRT 2, 3
Do not treat tumors where PTV overlaps trachea or main bronchi (ultracentral location) due to unacceptable toxicity risk 5
Ensure adequate follow-up beyond 2 years when treating central structures, as severe bronchial stenosis and fistula may occur late when large bronchi receive >80 Gy equivalent 4