SBRT for Cholangiocarcinoma Abutting the Diaphragm
SBRT can be used for cholangiocarcinoma abutting the diaphragm, though caution is required and hydrodissection techniques may be necessary to safely treat lesions in this location. 1, 2
Key Considerations for Diaphragm-Adjacent Lesions
The NCCN guidelines explicitly acknowledge that lesions abutting key structures such as the diaphragm may be difficult locations for ablation, but hydrodissection techniques can be used to safely treat in some instances. 1 While this statement specifically addresses ablation, the same anatomical considerations apply to SBRT planning, where normal tissue constraints must be carefully respected.
Evidence Supporting SBRT Use in Cholangiocarcinoma
Guideline Recommendations
The French Association for the Study of the Liver recommends SBRT for unique intrahepatic cholangiocarcinoma lesions less than 5 cm when surgical resection is not possible, with strong expert agreement. 1, 2
SBRT demonstrates promising efficacy for hilar (perihilar) cholangiocarcinoma with 2-year local control rates of 47-78%, according to the American College of Radiology. 2
Most tumors, irrespective of their location, may be amenable to SBRT, intensity-modulated radiation therapy, or conformal external beam radiation therapy. 1
Clinical Outcomes
Pooled 1-year local control rates for SBRT in cholangiocarcinoma are 78.6-83.4%, with median overall survival of 13.6-17 months. 3, 4, 5
Response rates reach 46.4% with disease control rates of 89.3% in intrahepatic cholangiocarcinoma treated with SBRT. 6
Toxicity is generally acceptable and manageable, with most studies reporting grade ≥3 toxicity in less than 10% acutely and 10-20% late toxicity (primarily gastrointestinal). 3, 4, 5
Dosing Recommendations
SBRT dosing is typically 30-50 Gy in 3-5 fractions, depending on the ability to meet normal organ constraints and underlying liver function. 1
The median prescription dose in clinical studies is 45 Gy (range 36-54 Gy) in 3-5 fractions. 6, 4, 5
Studies using equivalent dose in 2 Gy per fraction (EQD2) ≥71.3 Gy achieve 1-year local control of 81.8% compared to 74.7% with lower doses. 4
Critical Planning Considerations for Diaphragm-Adjacent Tumors
The panel emphasizes that caution should be exercised when treating lesions near the diaphragm to decrease complications. 1
Technical Strategies
Hydrodissection techniques can enable safe treatment of lesions abutting critical structures including the diaphragm. 1, 2
Ensure sufficient uninvolved liver volume and strict adherence to liver radiation dose constraints. 1
Advanced dose calculation algorithms and planning organ at risk volume (PRV) margins should be used for critical structures. 7
Patient Selection
Solitary intrahepatic lesions less than 5 cm represent the best candidates for SBRT. 2
There is no strict size limit if sufficient uninvolved liver exists and dose constraints can be respected. 1
Most safety and efficacy data are available for patients with Child-Pugh A liver function; limited data exist for Child-Pugh B. 1
Integration with Systemic Therapy
SBRT should be combined with systemic chemotherapy, particularly gemcitabine plus cisplatin, which remains the standard first-line systemic therapy. 1, 2
First-line cisplatin-gemcitabine with durvalumab or pembrolizumab provides better overall survival than chemotherapy alone. 1
SBRT is frequently used as salvage treatment, with 28.6-66.7% of patients receiving previous systemic or local treatments. 8
Critical Pitfalls to Avoid
Do not use SBRT for patients with Child-Pugh C cirrhosis, as safety has not been established in this population with very poor prognosis. 1, 2
Avoid conventional low-dose palliative radiation (8 Gy in 1 fraction) for cholangiocarcinoma, as this achieves suboptimal local control. 2, 9
Ensure multidisciplinary tumor board evaluation confirms unresectability before proceeding with SBRT. 2
For lesions abutting the diaphragm specifically, verify that respiratory motion management is adequate and that diaphragm dose constraints can be met. 1