Early Liver Toxicity and Dosimetric Correlates After Stereotactic Body Radiotherapy for Liver Metastases
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ABSTRACT Purpose Stereotactic body radiotherapy (SBRT) is increasingly used for the treatment of liver metastases; however, concerns regarding radiation-induced liver toxicity persist. This study aimed to evaluate early biochemical liver toxicity following SBRT for liver metastases and to identify clinical and dosimetric factors associated with liver function changes and survival outcomes. Methods Thirty-eight patients with liver metastases treated with SBRT between 2021-2024 were retrospectively analyzed. Biochemical liver function parameters, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), albumin, and international normalized ratio (INR), were assessed at the first and third months after SBRT. Dosimetric parameters such as mean liver dose, low- and intermediate-dose liver volumes (V5, V15, V20, V40), planning target volume (PTV), and biologically effective dose (BED) were recorded. Survival analyses were performed using Cox regression models with Firth’s penalized likelihood approach. Results No cases of clinically significant liver toxicity were observed during the first three months following SBRT. Although mild increases in AST and GGT levels were noted, these changes were predominantly subclinical and were not associated with deterioration in liver synthetic function. The majority of patients (74%) demonstrated no worsening in any liver enzyme or albumin level. No significant associations were identified between liver toxicity and dosimetric parameters, including mean liver dose and dose–volume metrics. Male sex was associated with biochemical worsening but did not result in clinically meaningful hepatic toxicity. Survival analyses identified the presence of a single extrahepatic metastatic site and larger PTV volume as independent adverse prognostic factors, whereas liver dosimetric parameters were not associated with survival. Conclusion Liver-directed SBRT can be safely delivered in patients with metastatic disease without clinically meaningful early hepatic toxicity. When contemporary treatment planning and established liver dose constraints are applied, SBRT preserves liver function and represents a safe and effective locoregional treatment option for liver metastases. Corresponding author: Kimia Çepni, e-mail: kimiagh@gmail.com Received: 27.11.2025 Accepted 15.12.2025
