Can looking at density differences between liver parenchyma and oligometastatic lesions predict outcomes and toxicities in patients receiving stereotactic body radiation therapy for metastatectomy

479Background: Stereotactic body radiation therapy (SBRT) has found utility in oligometastatic liver lesions by providing excellent local control in most patients. These tumors are not routinely biopsied to evaluate for histologic grade due to high risk of seeding. Non-invasive pre-treatment radiographic findings may be able to identify a subset of patients at higher risk of local recurrence. Methods: Retrospective review of an IRB-approved database of liver metastases treated with SBRT yielded 55 patients for final analysis. Liver parenchyma and metastatic liver lesions were contoured using MIM version 6.6.5. Receiver Operating Characteristic curves and mean values were used to generate binary cutoffs for toxicities and Kaplan-Meier analysis, respectively. Computer Tomography features, like density, skew, kurtosis, variance, and volume, based on our pre-SBRT planning liver protocol images and their relationship with outcomes and toxicities were examined. Results: Largepre-SBRT density differences between...