Proton Beam Radiotherapy Combined with Anti-PD1/PDL1 Immune Checkpoint Inhibitors for Advanced Hepatocellular Carcinoma

Anti-Programmed cell Death protein 1 (Anti-PD1) or Programmed Death-Ligand 1 (PDL1) immune checkpoint inhibitors provide treatment options for advanced HCC patients with low response rates. Combination therapy is becoming a major issue to improve the unmet need. Proton beam radiotherapy (PBT) could effectively control the local tumor with a low-risk injury to peripheral liver parenchyma. We retrospectively reviewed the patients who have received PBT combined with anti-PD1/PDL1 to evaluate the efficacy and safety of the advanced HCC patients. This study reviewed 29 advanced HCC patients who have received PBT and anti-PD1/PDL1 during 2016 and 2019. All were Child-Pugh A and performance status 0-1. Seventeen patients (58.6%) had extrahepatic spreading. Concurrent PBT started during anti-PD1/PDL1 with a median of 96.6 grays equivalent dose. The PBT field covered all tumors in 13 (44.8%) patients under curative intent. Other patients (55.2%) received palliative PBT that covered only the principal tumors. All patients have completed the concurrent PBT protocol. The median anti-PD1/PDL1 duration was 3.9 months. After a median follow-up of 13.2 months, the rates of 1-year PBT infield tumor control, 1-year outfield tumor control, and overall response were 90.5%, 90.9%, and 61.5%, and 70.8%, 69.2%, and 43.8%, respectively for curative-intent and palliative-control PBT. Complete response was found in 4 (30.8%) curative-intent and 1 (6.3%) palliative-control patients. The median overall progression-free survival was 27.2 months for curative-intent patients and 15.9 months for palliative-control patients. The overall survival was non-reached for both groups. The ALBI grade and Child-Pugh score change at 3-month and 6-month after PBT initiation were nonsignificant. No unexpected adverse event occurred except nine patients (31.0%) had treatment-related adverse events higher than or equal to Grade 3, including 2 (6.9%) had a radiation-induced liver injury. PBT combined with anti-PD1/PDL1 was safe without unexpected adverse events. The concurrent therapy could effectively treat advanced HCC through sustained local tumor necrosis and effective systemic tumor control for the patients who received curative-intent or palliative-control PBT combined with anti-PD1/PDL1.