What is the stereotactic body radiation therapy (SBRT) dose for liver metastases?

From the Guidelines

Stereotactic Body Radiation Therapy (SBRT) for liver metastases typically delivers 45-60 Gy in 3-5 fractions, with the most common regimen being 50 Gy in 5 fractions (10 Gy per fraction) 1. When considering SBRT for liver metastases, it is essential to evaluate the size and location of the lesions, as well as the patient's overall health and performance status.

• For smaller lesions (<3 cm) away from critical structures, higher doses of 54-60 Gy may be used, while lesions near sensitive organs like the stomach or bowel might receive lower doses of 40-45 Gy 1.
• Treatment is usually delivered every other day or three times per week to allow for normal tissue recovery.
• Dose constraints must be carefully observed for surrounding organs, including uninvolved liver (mean dose <15-18 Gy), stomach and small bowel (maximum point dose <30 Gy), and kidneys (mean dose <15 Gy) 1. The effectiveness of SBRT for liver metastases is based on the radiobiological advantage of high-dose per fraction treatments, which overcome the traditionally radioresistant nature of liver metastases, as noted in a systematic review with a meta-analysis of SBRT 1.
• This approach allows for ablative doses while minimizing toxicity through precise targeting and rapid dose fall-off outside the target volume, making it particularly valuable for patients with oligometastatic disease or those unsuitable for surgery 1. It is crucial to consider the patient's individual characteristics, such as tumor size, location, and overall health, when determining the optimal SBRT dose and fractionation schedule, as recommended by the NCCN guidelines for hepatobiliary cancers 1.

From the Research

SBRT Dose for Liver Metastases

• The prescribed dose for SBRT in liver metastases varies, with a median dose of 45 Gy delivered in a median of 3 fractions 2.
• A study using CyberKnife SBRT typically prescribed a dose of 60 Gy in four fractions to 95% of the target volume 3.
• Another study used a median cumulative dose of 35 Gy and a median single dose of 7 Gy 4.
• The biologically effective dose (BED10) is also an important factor, with BED10 ≥ 100 Gy associated with improved overall survival (OS) and local control (LC) 2.

Factors Affecting SBRT Dose

• Tumor volume is a significant factor, with smaller tumor volumes (< 40 cm3) correlating with improved OS and LC 2.
• The primary tumor histology also affects OS, with colorectal, breast, and gynecological metastases having better outcomes than lung, gastrointestinal, and pancreatic primaries 2.
• Dose fractionation and delivery techniques, such as motion management and advanced radiotherapy approaches, can impact the effectiveness and safety of SBRT 5.

Clinical Outcomes

• SBRT for liver metastases has shown promising clinical outcomes, with reasonable LC and OS rates [(2,3,4)].
• The 1-year LC and OS rates were 90% and 80%, respectively, in a study using CyberKnife SBRT 3.
• Median OS was 20.4 months and median LC was 35.1 months in a cohort of 115 patients with 150 irradiated liver metastases 4.