ESTRO 2024 - Abstract Book

S2195

Clinical - Upper GI

ESTRO 2024

utilized:the Liver Imaging Reporting and Data System (LI-RADS) and modified Response Evaluation Criteria in Solid Tumors(mRECIST). Both systems are founded on the two-dimensional assessment of arterial enhancement of HCC lesions. Li-RADS categorizes the treatment response (TR) into three categories TR-non-viable, TR-viable and TR equivocal, and mostly employed after local therapies as thermal ablation or TACE (1). Conversely, mRECIST categorizes the treatment response into Complete response (CR), Partial response (PR), stable disease (SD), and disease progressive disease (PD) and is primarily used in response assessment of systemic therapies (2). the response of HCC following SBRT differs from other local ablation tools and may pose challenges due to variations in response pattern and timing. In the current analysis, we aim to analyze the three-dimensional volumetric changes in HCC following SBRT and timing for the best response.

Material/Methods:

We conducted a retrospective assessment of patients diagnosed with HCC who received SBRT for liver lesions in our center. Initially, we reported the Local control rate of all treated lesions. Further, we imported the assessment imaging, including CT and/or MRI scans, into the treatment planning System (TPS) followed by delineating the arterial enhancement of the irradiated lesions or the hypodense lesions in case lesions did not exhibit enhancement at the time of diagnosis. Finally, we analyzed the change in the volume of treated lesions over time.

Results:

Figure-1 relative volume change after SBRT

Sixty-two lesions from 49 patients were analyzed (Table 1). The local control rate after 1,2 and 3 years was: 95.7%, 95.7%, and 82%, respectively. Based on mRECIST the best response pattern for those lesions was: 40 CR (65%), 10 PR (16%), 10 SD (16), and 2 PD (3%). Only three lesions experienced progression after SBRT at 4.9, 5.3, and 27.3 months after SBRT. The median time to achieve the best response following SBRT was 3.6 months (interquartile range: 2.46-5.7 Months).