SBRT treatment response in patients with HCC undergoing transplant

Summary: Hepatocellular carcinoma incidence has increased worldwide with an estimated incidence of 42,000 cases in the United States in 2024. Traditionally, surgical resection and transplant were gold standard options for treatment however the development of targeted therapies including TACE, Y-90, and SBRT have allowed for tumor control as bridge to transplant if patients are suitable candidates. Prior studies have been done looking at pathologic response in patients who have undergone SBRT and looking at radiologic response post-treatment. However, not much has been done at investigating the relationship between radiologic and pathologic responses in patients who have undergone SBRT and then transplant. Patients treated with stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma since 2013 who then underwent transplant were retrospectively analyzed for explant pathology and post-treatment imaging results. Other data collected included lab values, other liver targeted treatments, treatment fractionations, doses, and volumes in treatment plan, and mortality. Patients (n=42) had 49 separate SBRT treatment courses to 66 PTVs for HCC and underwent liver transplantation. Patients had a mean age of 61.1 ± 6.51 years (range 40-73 years) with 33 male patients and 9 female patients. Most common HCC etiologies included MASLD (n=12, 28.6%), Alcohol (n=10, 23.8%), and HCV (n=8, 19%). Patients were treated with either CT-based SBRT (n=36) or MRI-based SBRT (n=6) with a majority of patients receiving 50 Gy in 5 fractions. Transplant occurred 194 ±118 days after end of SBRT treatment with range of 2-417 days including one patient who underwent transplant prior to end of planned SBRT treatment. Most patients underwent DDLT (n=38) with two also undergoing SLKT, three underwent LDLT, and one patient underwent ELRA. Of the 41 patients with pathology reports available looking at 65 PTVs, 26 (40%) had complete response of SBRT treated lesions, 25 (38.5%) had partial response, and 14 (21.5%) had no response. Looking at 40 patients with post-treatment imaging prior to transplant, 22 volumes had complete response, 21 volumes had partial response, and 13 volumes had stable response. Five volumes from three patients had local progressive disease. Patients treated with SBRT for HCC have acceptable pathologic and radiologic responses based on explant pathology and post-treatment imaging. Further analyses will investigate predictors of pathologic and radiologic response as well as specific toxicity profiles in responders versus non-responders. Lastly given increased use of MRI based treatments, further investigations will be done looking at differences in response and toxicities between CT based and MRI based treatments. Evrosina I. Isaac (she/her/hers), MD (Presenting Author) - VCU Department of Radiation Oncology; Ross Taylor, MD (Co-Author) - Baptist Health Quality Network Lynn Cancer Institute; Joshua Dault, MD (Co-Author) - Capital Regional Cancer Center; Timothy J. Harris, MD, PhD (Co-Author) - VCU Department of Radiation Oncology; Emma C.. Fields, MD (Co-Author) - VCU Department of Radiation Oncology