ESTRO 2024 - Abstract Book

S2134

Clinical - Upper GI

ESTRO 2024

Radiation-induced lymphopenia predicts poor survival in HCC patients treated with radiotherapy

Landon L. Chan 1 , Vanessa T.Y. Yeung 1 , Frankie Mo 1 , Darren M.C. Poon 1 , Macy Tong 1 , Florence S.T. Mok 1 , Winnie M.T. Soo 1 , Daisy C.M. Lam 1 , Benjamin H.W. Lam 1 , David R. Johnson 1 , Wesley K.Y. Wong 1 , Allen C.C. Chen 1 , Stephen L. Chan 1,2 1 The Chinese University of Hong Kong, Department of Clinical Oncology, New Territories, Hong Kong. 2 Hong Kong Cancer Institute, State Key Laboratory of Translational Oncology, New Territories, Hong Kong

Purpose/Objective:

Stereotactic body radiation therapy (SBRT) in hepatocellular carcinoma (HCC) has emerged as a promising locoregional therapy either as a stand-alone treatment or as a sequential treatment with systemic therapy [1, 2]. Recent works in radiobiology has shown that immunogenic cell death is one of the mechanisms to cause tumour cell death following radiation [3]. As a major player of immunogenic cell death, the amount of circulating lymphocytes following radiation is therefore a potential important prognostic biomarker for patient outcome. Being exquisitely sensitive to even low-dose of radiation, radiation-induced lymphopenia has been linked to inferior oncological outcomes in many cancers, but there are a paucity of studies exploring the relationship between radiation-induced lymphopenia and clinical outcomes in HCC patients treated with SBRT [4]. In this study, we sought to evaluate the rate of severe radiation-induced lymphopenia, its impact on overall survival, and factors associated with severe radiation-induced lymphopenia in HCC patients who were treated by SBRT. Eligible patients who received SBRT to the liver for HCC from January 2013 to December 2021 were recruited at the Prince of Wales Hospital, Hong Kong. Patients were excluded if they had metastatic disease, had more than one course of radiotherapy to the liver, or concurrent malignancies. Patients’ characteristics, BCLC stage, pre - (taken 1 month before radiotherapy) and post-treatment (taken within 3 months after radiotherapy) laboratories findings, radiotherapy prescription parameters were collected. Severe lymphopenia was defined as grade 3 or 4 lymphopenia according to the common terminology criteria for adverse events (CTCAE) version 5.0 (i.e. <0.5x10^9/L lymphocytes). The primary endpoint was overall survival (OS), which was defined as the time from the first day of radiotherapy to death of any cause. OS was assessed using Kaplan-Meier Method. Prognostic factors were assessed using univariate and multivariate Cox Proportional Hazards Model. Univariate variables that had a p-value less than 0.1 were included in the multivariate analysis. Stepwise model selection by AIC was used to pick up the most parsimonious multivariate model. Logistic regression was used to correlate radiotherapy prescription parameters and the occurrence of severe radiation-induced lymphopenia. All statistical analyses were performed using R Statistical Software (v4.2.0; R Core Team 2022) [5]. Material/Methods:

Results:

Total 107 patients were recruited. There were 80 (74.8%) males. Median age at the time of radiotherapy was 72 (IQR: 65-79). Predominantly patients had HBV etiology (75.7%). 22 (20.6%), 66 (68.5%) and 46 (43.0%) had previous surgery, transarterial chemoembolization (TACE) or ablation respectively. 65 (60.7%), 28 (26.2%), 13 (12.1%) patients had BCLC stage 0/A, B and C respectively. The median size of tumour treated is 2.6cm (IQR: 1.5-3.4). 95 (88.8%) patients had baseline Child-Pugh liver function A.