How can hydrodissection (hydrodissection) be used in Stereotactic Body Radiation Therapy (SBRT) for tumors abutting the diaphragm?

Hydrodissection for SBRT in Tumors Abutting the Diaphragm

Hydrodissection can be used to safely create physical separation between tumors abutting the diaphragm and adjacent organs at risk, enabling delivery of ablative SBRT doses while meeting normal tissue constraints. 1, 2

Technical Approach to Hydrodissection

The technique involves placement of a drainage catheter followed by injection of fluid (typically saline or dextrose solution) to create a minimum 10 mm separation between the gross tumor volume and the organ at risk. 3 This displacement must be:

• Established during initial simulation imaging with hydrodissection performed on the same day as CT simulation 3
• Reproduced at each SBRT treatment session by re-injecting fluid through the indwelling catheter 3
• Maintained throughout the entire treatment boundary to achieve complete displacement 3

The catheter remains in place throughout the treatment course and is removed after the final SBRT fraction. 3

Clinical Evidence Supporting Safety and Efficacy

A prospective series of 31 patients demonstrated that hydrodissection achieved:

• Median displacement of 32.4 mm at SBRT delivery (compared to 4.1 mm without intervention, P < .001) 3
• Complete displacement (≥10 mm across entire boundary) in 71% of patients 3
• Single-fraction ablative SBRT delivery in 81% of patients who would otherwise have required dose de-escalation 3
• Zero procedure-related complications within 30 days and no organ-at-risk toxicities at median 33-month follow-up 3

Integration with SBRT Planning for Hepatobiliary Tumors

For tumors abutting the diaphragm in the hepatobiliary region specifically:

• SBRT dosing of 30-50 Gy in 3-5 fractions is standard, with exact dose determined by ability to meet normal organ constraints and underlying liver function 1, 2
• Most tumors regardless of location may be amenable to SBRT if sufficient uninvolved liver exists and dose constraints can be respected 1, 2
• Hydrodissection enables treatment of lesions that would otherwise be contraindicated due to proximity to critical structures including the diaphragm 1, 2

Critical Planning Considerations

Respiratory motion management is essential for diaphragm-adjacent tumors. 2 The planning approach must account for:

• 4D-CT imaging to capture full respiratory excursion of both tumor and diaphragm 1
• Verification that diaphragm dose constraints can be met after hydrodissection displacement 2
• Strict adherence to liver radiation dose constraints, particularly for patients with Child-Pugh B cirrhosis who may require dose modifications 1, 2

Patient Selection Criteria

Hydrodissection is most appropriate for:

• Lesions <5 cm where surgical resection is not possible 2
• Patients with Child-Pugh A liver function (most safety data available) or carefully selected Child-Pugh B patients 1, 2
• Tumors where at least 10 mm separation can be achieved across the entire tumor-diaphragm interface 3

Absolute contraindications include:

• Child-Pugh C cirrhosis (safety not established, very poor prognosis) 1, 2
• Active coagulopathy or inability to safely place drainage catheter 3

Common Pitfalls to Avoid

• Do not attempt SBRT without adequate displacement verification at each treatment fraction, as displacement must be reproduced consistently 3
• Do not use conventional low-dose palliative radiation (e.g., 8 Gy in 1 fraction) when ablative SBRT with hydrodissection is feasible, as this achieves suboptimal local control 2, 4
• Do not proceed if respiratory motion cannot be adequately managed, as diaphragmatic excursion may compromise the hydrodissection separation 2
• Ensure multidisciplinary review confirms unresectability before committing to SBRT, as surgical resection remains preferred when feasible 1