3453 - External Beam Radiotherapy (EBRT) + Immunotherapy (IO) in the Management of Hepatobiliary Malignancies: A Meta-Analysis of Treatment Response Rates

02:30pm - 03:45pm PT

Hall F

Screen: 14

POSTER

Presenter(s)

Juan Jose Juarez Vignon Whaley, MD - MetroWest Medical Center, Sudbury, MA

J. J. Juarez Vignon Whaley^1,2, M. L. Peters^1,2, and M. J. Abrams^2,3; ¹Department of Medical Oncology, Beth Israel Deaconess Medical Center, Boston, MA, ²Harvard Medical School, Boston, MA, ³Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Boston, MA

Purpose/Objective(s):

External beam radiotherapy (EBRT) combined with immunotherapy (IO) has emerged as a promising treatment strategy for managing advanced hepatobiliary (HPB) malignancies, including hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA). This meta-analysis aims to report the treatment response rates of EBRT + IO for unresectable or advanced HCC and CCA. We hypothesize that the combination of EBRT and IO will demonstrate a synergistic effect with significant treatment response rates in advanced HCC and CCA.

Materials/Methods:

We conducted a systematic search of PubMed, Web of Science, and Cochrane databases to identify relevant studies. Patient characteristics, and measures of treatment response including objective response rate (ORR), and disease control rate (DCR) were extracted. Pooled ORR and DCR were calculated using random effect model and assessed for study heterogeneity. Subgroup analyses comparing study type (clinical trials vs retrospective studies) and EBRT target (primary lesion only vs primary + metastasis) were performed.

Results:

Among 528 studies screened for HCC, 22 studies (10 clinical trials and 12 retrospective studies) were identified. One retrospective study did not report ORR, and another lacked DCR data. Out of the 970 patients included, 842 reported ORR and 845 DCR. Most studies (19) used photon therapy, with one using protons and two using a combination of both. Pooled analysis of all studies demonstrated an ORR of 58% (95%CI 50-65%) and a DCR of 79% (95%CI 72-85%). Subgroup analyses by study type showed no significant differences in ORR (54% vs 61%, p = 0.45) or DCR (83% vs 78%, p = 0.52) between clinical trials and retrospective studies. Similarly, no differences were observed between EBRT targeting the primary lesion only versus primary + metastasis for ORR (58% vs 59%, p = 0.94) and DCR (81% vs 77%, p = 0.62).

For CCA, among the 76 studies screened only 3 (2 clinical trials) met inclusion criteria, with a total of 136 patients. The pooled ORR was 32% (95% CI 10-68%) and the DCR was 70% (95% CI 21-95%). Due to sample size, subgroup analysis was not performed.

Conclusion:

This meta-analysis provides the first pooled analysis of EBRT + IO in advanced HPB malignancies. Our findings suggest that EBRT + IO is effective in achieving adequate disease control in advanced HCC, comparable to systemic therapy (IMbrave150 and HIMALAYA). The absence of significant differences between study types suggests that retrospective studies adequately represent real-world populations, supporting the generalizability of EBRT + IO response rates beyond controlled clinical trial settings. These findings support further investigation into EBRT as a method of potentiating the effect of IO. While no differences were observed between EBRT targets, direct comparative trials are necessary to validate these findings. Lastly, further prospective research is required to understand the potential effect of EBRT + IO in CCA.