Can Stereotactic Body Radiation Therapy (SBRT) be used to treat a hepatic tumor abutting the diaphragm?

SBRT for Hepatic Tumors Abutting the Diaphragm

Yes, SBRT can be safely and effectively used for hepatic tumors abutting the diaphragm, regardless of tumor location, provided that sufficient uninvolved liver exists and radiation dose constraints can be respected. 1

Guideline-Based Recommendation

The NCCN explicitly states that all tumors irrespective of their location may be amenable to SBRT, IMRT, or 3D conformal radiation therapy. 1 This location-agnostic approach applies specifically to hepatic tumors abutting the diaphragm, with the critical caveat that normal tissue constraints must be achievable. 1

Key Technical Considerations for Diaphragm-Adjacent Lesions

• Hydrodissection techniques can enable safe treatment of lesions abutting the diaphragm by creating physical separation between the tumor and adjacent organs at risk, allowing delivery of ablative SBRT doses while meeting normal tissue constraints. 2

• Respiratory motion management is essential for diaphragm-adjacent tumors, requiring 4D-CT imaging to capture full respiratory excursion of both tumor and diaphragm. 2

• Verification that diaphragm dose constraints can be met after any hydrodissection displacement is crucial before proceeding with treatment. 2

Treatment Algorithm

Step 1: Confirm Eligibility

• Verify unresectability through multidisciplinary tumor board evaluation, as surgical resection remains preferred when feasible. 3, 2
• Assess liver function: Child-Pugh A patients are optimal candidates; Child-Pugh B patients can be treated with dose modifications and strict constraint adherence. 1
• Child-Pugh C cirrhosis is an absolute contraindication to SBRT, as safety has not been established in this population with very poor prognosis. 1, 4

Step 2: Dosing Strategy

• Standard SBRT dosing is 30-50 Gy delivered in 3-5 fractions, with exact dose determined by ability to meet normal organ constraints and underlying liver function. 3, 2
• SBRT (1-5 fractions) is often used for patients with up to 3 tumors. 1
• There is no strict size limit if sufficient uninvolved liver exists and dose constraints can be respected. 1, 2

Step 3: Critical Dose Constraints

• Mean liver dose should be kept at 15-20 Gy depending on baseline liver function, with stricter constraints for compromised hepatic reserve. 4
• Ensure sufficient uninvolved liver volume and strict adherence to liver radiation dose constraints. 2
• For Child-Pugh B patients, dose modifications and strict dose constraint adherence are required. 1

Step 4: Consider Hydrodissection

• For lesions <5 cm where surgical resection is not possible, hydrodissection can be used to safely create physical separation from the diaphragm. 2
• Verify that displacement can be reproduced consistently at each treatment fraction. 2

Clinical Outcomes Supporting SBRT Use

• SBRT demonstrates excellent local control rates, with 2-year local control rates of 94.6% reported in phase II trials of patients with inoperable HCC. 1
• Overall survival rates of 92.9% at 1 year and 58.6% at 3 years have been achieved in patients with small HCC ineligible for local therapy or surgery. 1
• SBRT provides superior local control compared to TACE (HR: 0.25; 95% CI: 0.09-0.67; p = 0.006) with comparable overall survival. 5

Critical Pitfalls to Avoid

• Never use conventional low-dose palliative radiation (8 Gy in 1 fraction) for hepatic tumors when ablative SBRT is feasible, as this achieves suboptimal local control. 3, 2, 4
• Do not treat patients with Child-Pugh C cirrhosis with liver SBRT. 1, 4
• Ensure adequate respiratory motion management is in place for diaphragm-adjacent tumors to account for tumor and diaphragm movement during breathing. 2
• Treatment at centers with experience is recommended for hypofractionated EBRT with photons or protons for intrahepatic tumors. 1

Integration with Systemic Therapy

• SBRT should be considered as an alternative to ablation/embolization techniques or when these therapies have failed or are contraindicated. 1
• There should be no extrahepatic disease or it should be minimal and addressed in a comprehensive management plan. 1
• SBRT has been shown to be an effective bridging therapy for patients with HCC and cirrhosis awaiting liver transplant. 1