# Effectiveness, safety, and the abscopal effect of stereotactic body radiation therapy combined with immune checkpoint inhibitors in advanced gastrointestinal cancers: a systematic review and meta-analysis

## TL;DR

Combining stereotactic body radiation therapy with immune checkpoint inhibitors improves outcomes in advanced gastrointestinal cancers, with manageable side effects.

## Contribution

This study provides a meta-analysis showing that combining SBRT and ICIs enhances efficacy and survival in advanced GI cancers.

## Key findings

- SBRT+ICIs significantly improved objective response rate compared to controls.
- The combination therapy reduced the risk of death and disease progression.
- Grade ≥3 treatment-related adverse events were not significantly increased.

## Abstract

The efficacy of immune checkpoint inhibitors (ICIs) in advanced gastrointestinal (GI) cancers, especially microsatellite-stable tumors, is limited. Stereotactic body radiation therapy (SBRT) may enhance ICIs’ antitumor immune response by promoting immunogenic cell death. This meta-analysis evaluated the efficacy, safety, and abscopal effect of combining SBRT and ICIs in advanced GI malignancies.

A literature search across PubMed, Embase, and Cochrane Library up to November 23, 2025, was conducted. Primary endpoints were objective response rate (ORR) and progression-free survival (PFS); secondary outcomes included overall survival (OS), disease control rate (DCR), grade ≥3 treatment-related adverse events (TRAEs), and abscopal effect rate. Random-effects models and I² statistics were used for analysis.

Twenty-five studies were included in the final analysis. Risk of bias assessment indicated generally high methodological quality across included studies. SBRT+ICIs significantly improved the objective response rate (OR 5.30, 95% CI: 2.19–12.84) compared to controls. The combination therapy robustly reduced the risk of death (HR 0.43, 95% CI: 0.33–0.55) and disease progression (HR 0.43, 95% CI: 0.35–0.54). Importantly, the risk of grade ≥3 treatment-related adverse events was not significantly increased compared to control groups (pooled RD -0.09, 95% CI: -0.35 to 0.18). The reported abscopal effect rate varied across studies, with a mean of 26.2%.

SBRT+ICIs improves efficacy and survival in advanced GI cancers, with manageable safety, especially in hepatocellular carcinoma. Further validation in randomized trials and optimization for less responsive tumors is needed.