What are the recommended Stereotactic Body Radiation Therapy (SBRT) doses for recurrent or retreated head and neck, liver, and renal tumors, as well as lymph nodes?

SBRT Dosing for Recurrent/Retreated Head and Neck, Liver, Renal Tumors, and Lymph Nodes

Head and Neck Tumors (Recurrent/Retreated)

For recurrent head and neck cancers in previously irradiated fields, deliver 30-44 Gy in 5 fractions using SBRT, with higher doses (40-44 Gy) reserved for smaller tumors (<25 mL) where local control is significantly superior. 1, 2

Dose-Volume Relationships

• Tumors <25 mL achieve 77% local control at 6 months and 59% at 1 year with median doses of 40 Gy in 5 fractions 2
• Larger tumors (>25 mL) demonstrate significantly worse local control (p=0.030), and optimal dosing remains undefined for this subset 2
• The typical dose range is 30-44 Gy delivered in 5 fractions, with interquartile range of 30-44 Gy across multiple histologies 2

Safety Profile in Reirradiation

• Acute grade 3 toxicity occurs in 15% of patients, with late grade 3 toxicity in only 6% 2
• Critical warning: Patients with prior radiotherapy face significant risk of severe late complications including fatal hemorrhage, particularly when reirradiation occurs within 24 months of initial treatment 3
• Two patients in one series died from massive pharyngeal hemorrhage at 5 and 28 months post-SBRT, both having received prior radiotherapy 3
• All severe late complications (necrosis, hemorrhage) occurred exclusively in previously irradiated patients 3

Treatment Planning Considerations

• Target volumes typically range from 0.7-78.1 cm³ (median 11.6 cm³) 3
• Complete response rates of 32.4% and partial response rates of 38.6% are achievable 3
• Overall survival at 12 and 24 months is 70.6% and 58.3% respectively, with better outcomes in patients without recent prior radiotherapy 3

Liver Tumors (Primary and Metastatic)

For liver tumors, deliver 60 Gy in 3 fractions for metastases or recurrent disease, ensuring adequate normal liver volume preservation and strict adherence to gastrointestinal dose constraints. 1, 4

Dose Escalation and Safety

• Phase I trials safely escalated to 60 Gy in 3 fractions for liver metastases 4
• Eligibility criteria: 1-3 discrete lesions with aggregate tumor diameter <6 cm 4
• Planning target volume must include gross tumor volume plus minimum 5-mm radial and 10-mm superior-inferior margins 4

Critical Dose Constraints

• Maximum point dose to gastrointestinal mucosa is the primary limitation, not mean dose 4
• Adequate normal liver volume must be preserved prior to therapy 4
• Respiratory control is mandatory for treatment delivery 4

Response Assessment Timing

• Radiographic evaluation is extremely difficult within the first few months post-SBRT 4
• Response analysis requires 4-6 months after SBRT completion 4

Special Population Considerations

• Child-Pugh class A patients are the primary candidates with established safety data 5
• Child-Pugh class B patients can be treated but require dose modifications and strict dose constraint adherence 5, 6
• Child-Pugh class C cirrhosis is a contraindication—safety has not been established and prognosis is very poor 5, 6

Renal Tumors

For renal cell carcinoma, deliver 24 Gy in a single fraction using simultaneous integrated boost technique, achieving 90% 1-year local control and 85% crude local control rates. 1, 4

Radiobiological Advantage

• Renal cell carcinoma is traditionally radioresistant but shows excellent response to SBRT with 2-year local control rates of 90% 1, 6
• The high biological effective dose delivered by SBRT overcomes the inherent radioresistance 6

Clinical Applications

• SBRT serves as an alternative to surgery for primary renal tumors 4
• Effective as cytoreductive therapy for metastatic sites 4
• Single-fraction approach (24 Gy) is appropriate for spinal metastases from renal cell carcinoma 1

Lymph Nodes (Recurrent/Retreated)

For recurrent cervical lymph nodes, deliver 30 Gy in 3-8 fractions, with dose selection based on prior radiation exposure and nodal volume. 3

Dose Fractionation

• Prescribed doses range from 19.5-42 Gy (median 30 Gy) in 3-8 fractions for consecutive days 3
• Cervical lymph nodes represent a common retreatment site (6 of 34 patients in one series) 3

Outcomes

• Complete response rate of 32.4% and partial response rate of 38.6% 3
• Treatment is well tolerated without significant acute complications 3

Universal SBRT Principles for Reirradiation

Biological Effective Dose Requirements

• Target BED of at least 50 Gy to optimize local control rates of approximately 90% at 1 year 1
• For lung tumors (if applicable), BED10 should be at least 100 Gy, with optimal ranges of 106-146 Gy 1, 7

Critical Pitfalls to Avoid

• Never use conventional low-dose palliative radiation (8 Gy in 1 fraction) for patients with longer expected survival—this achieves <50% 1-year local control for bulky tumors 1, 6
• Avoid reirradiation within 24 months of initial treatment when possible due to increased hemorrhage risk 3
• Do not exceed normal tissue tolerance doses, particularly for serial organs (spinal cord, gastrointestinal tract) 4
• Ensure adequate time interval (typically 6 weeks or less is preferred for postoperative settings, but longer intervals reduce toxicity in reirradiation) 5

Technical Requirements

• Use respiratory control for liver and upper abdominal tumors 4
• Employ image guidance and advanced treatment delivery technologies 6
• Verify treatment plans with quantitative dosimetry 8
• Use type B dose calculation algorithms for accurate planning 7