3442 - Proton Radiotherapy Alone vs. Combined with Immuno-Oncology Agents (Proton-IO) or Tyrosine Kinase Inhibitors (Proton-TKI) for Intermediate to Advanced-Stage Hepatocellular Carcinoma

02:30pm - 03:45pm PT

Hall F

Screen: 13

POSTER

Presenter(s)

Rodney Cheng-En Hsieh, MD, PhD - Chang Gung Memorial Hospital Linkou Branch, Taoyuan City, Taiwan

R. C. E. Hsieh¹, P. Y. Chen², C. H. Lin³, Y. C. Chang⁴, K. C. Tr?n⁵, and C. W. Lee⁶; ¹Departments of Medical Imaging and Radiological Sciences, Radiation Oncology, and Cancer Genome Research Center, Chang Gung Memorial Hospital at Linkou and Chang Gung University, Taoyuan City, Taiwan, ²Department of Radiation Oncology, Chang Gung Memorial Hospital at Linkou, Taoyuan City, Taiwan, ³MD Anderson Cancer Center, Houston, TX, ⁴Department of Radiation Oncology, Chang Gung Memorial Hospital, Keelung, Taiwan, ⁵Department of Radiation Oncology and Proton Therapy Center, Chang Gung Memorial Hospital at Linkou, Taoyuan City, Taiwan, ⁶Chang Gung Memorial Hospital at Linkou, Taoyuan City, Taiwan, Taiwan

Purpose/Objective(s): We aim to compare the outcomes of proton radiotherapy alone versus its combination with immuno-oncology agents (Proton-IO) or tyrosine kinase inhibitors (Proton-TKI) for the treatment of intermediate to advanced-stage hepatocellular carcinoma (HCC).

Materials/Methods: This retrospective study reviewed the medical records of 137 patients with Barcelona Clinic Liver Cancer (BCLC) stage B (N = 43) or C (N = 94) HCC who received proton radiotherapy alone (N = 64), Proton-IO (N = 44), or Proton-TKI (N = 29) at Linkou Chang Gung Memorial Hospital between 2020 and 2023. The most common dose fractionation schedules included 72.6 Cobalt Gray Equivalent (CGE) in 22 fractions (N = 123) and 66 CGE in 10 fractions (N = 8). Atezolizumab-bevacizumab (N = 33) and pembrolizumab (N = 5) were the most frequently used immuno-oncology agents, while tyrosine kinase inhibitors included lenvatinib (N = 16) and sorafenib (N = 13). Tumor vascular thrombosis was observed in 85 (62%) patients. Pretreatment Child-Pugh class A and B were documented in 125 (91%) and 12 (9%) patients, respectively.

Results: After a median follow-up of 20 months, patients treated with Proton-IO had a significantly higher 2-year overall survival (OS) rate compared to those treated with Proton-TKI or proton radiotherapy alone (79.2% vs. 46.4% vs. 53.0%, P = 0.008). We observed significantly higher 2-year progression-free survival (PFS; 45.1% vs. 13.8% vs. 17.1%, P < 0.001) and distant metastasis-free survival (DMFS; 81.6% vs. 61.1% vs. 64.3%, P = 0.016) rates in the Proton-IO group, compared to those treated with Proton-TKI or proton radiotherapy alone. No significant differences were observed in 2-year local control rates among the treatment groups (Proton-IO vs. Proton-TKI vs. Proton radiotherapy alone: 93.9% vs. 86.8% vs. 80.7%, P = 0.216). Multivariate analysis identified the use of immuno-oncology agents as a significant predictor of superior OS (P = 0.010), PFS (P < 0.001), and DMFS (P = 0.005), whereas a tumor size >10 cm was significantly associated with lower PFS (P = 0.013) and DMFS (P = 0.042).

Conclusion: For intermediate to advanced-stage HCC, proton radiotherapy combined with immuno-oncology agents was associated with superior OS, PFS, and DMFS rates, compared with proton irradiation alone or in combination with tyrosine kinase inhibitors.