Enhancing tumor control in liver metastases treated with SBRT: dosimetric predictors and clinical outcomes from a single-center analysis

Liver metastases, a hallmark of systemic disease, carry a poor prognosis despite advancements in systemic therapies. Stereotactic body radiation therapy (SBRT) has emerged as a promising local treatment, offering durable tumor control with minimal toxicity. However, the optimal dosimetric strategies to maximize outcomes remain an area of active investigation. This retrospective study evaluated 76 patients with 101 liver metastases treated with SBRT between November 2012 and June 2024. Dosimetric parameters were analyzed, including prescribed dose (PD) and dose metrics for planning target volume (PTV) and gross tumor volume (GTV), with doses converted to equivalent doses in 2 Gy fractions (EQD2, α/β = 10). Tumor control probability (TCP) models and survival outcomes were assessed, with a focus on the prognostic impact of dosimetric and clinical factors. Median overall survival (OS) was 33 months, with 1-year and 3-year OS rates of 74.1% and 39.4%, respectively. Freedom from local progression (FFLP) was 82.5% at 12 months. PD emerged as the strongest independent predictor of local control, with an optimal threshold of 77.44 Gy EQD2 significantly improving 1-year FFLP rates (96.8% vs. 67.2%; p = 0.007). Advanced motion management techniques, including internal breath-hold (iBH) with image-guided radiotherapy (IGRT), demonstrated superior local control outcomes. Predictive modeling confirmed PD as the most robust dosimetric metric, correlating with a high TCP and outperforming other dose metrics. Toxicity was minimal, with only 3.9% experiencing grade ≥ 3 adverse events. SBRT represents a highly effective and safe approach for liver metastases, with PD and advanced imaging emerging as pivotal determinants of tumor control. These findings underscore the importance of precise dosimetric planning and motion management in optimizing SBRT outcomes. This study provides a robust framework for personalized treatment strategies, contributing to the integration of SBRT as a cornerstone in the multidisciplinary management of liver metastases.