Radiation Oncology in upper GI Cancers

ESTRO 2026 Congress Report

By the ESTRO Upper GI Focus Group

The ESTRO 2026 annual meeting in Stockholm offered a comprehensive review of the evolving role of radiotherapy across gastrointestinal oncology. This report synthesises the most clinically relevant abstracts from Part I of the abstract book, selected to reflect both practice-changing data and emerging concepts in adaptive radiotherapy, multi-modal integration, and stereotactic ablative approaches. Abstracts are organised by disease site.

Online Adaptive Radiotherapy — the ARTEC Trial

The ARTEC trial (presented as a Proffered Paper) reported preliminary results of prospective, CBCT-based online adaptive radiotherapy (oART) for oesophageal cancer on the Ethos platform in 14 of 30 planned patients. The prescribed dose was 50.4 Gy in 28 fractions with concurrent carboplatin/paclitaxel. Adapted plans showed significant dosimetric improvements over the reference plan: PTVD99% increased by 10.2% (p<0.001) and CTVD99% by 1.2% (p=0.006), without increasing cardiac, pulmonary, or hepatic OAR doses. Acute grade 3 toxicity was 14.3% (two cases of severe dysphagia). These results validate daily online adaptation for oesophageal cancer as clinically feasible and dosimetrically superior to conventional IGRT — directly relevant for centres with the Ethos linear accelerator.^[1]

Cardiovascular Late Effects

A large real-world evidence study using the TriNetX database compared 13,209 radiotherapy-treated oesophageal cancer patients with 57,311 untreated controls. Radiotherapy was independently associated with new coronary artery disease (18.1% vs. 13.4%; HR 1.25), cerebrovascular events (8.4% vs. 5.7%; HR 1.36), and a composite vascular endpoint (23.2% vs. 16.8%; HR 1.29; all p<0.001).^[2] This population-level evidence reinforces the clinical imperative of cardiac dose optimisation, and complements institutional IMPT data demonstrating that intensity-modulated proton therapy reduces mean heart and lung dose by 51% and 55%, respectively, versus photon chemoradiotherapy.^[3]

Biomarkers and Predictive Models

Radiation-induced lymphopenia during neoadjuvant chemoradiotherapy was identified as a predictive biomarker for Nivolumab benefit,^[4] with 1-year OS of 88.3% and 1-year local control of 96.0% in the reported cohort. An AI-driven model using longitudinal CT imaging and chain-of-thought prompt learning achieved a pathological complete response (pCR) prediction accuracy of 88% at the preoperative time point, providing clinically actionable insights into organ preservation candidacy.^[5] Together, these abstracts advance the goal of biomarker-driven patient selection for both adjuvant immunotherapy and watch-and-wait strategies.

MR-Linac and Fractionation Strategies

A Toronto institutional series reported on 169 oesophageal cancer patients treated with a hybrid approach combining conventional photon delivery with an MR-linac adaptive boost; 95.3% completed treatment, illustrating the clinical feasibility of this investigational strategy.^[6] Separately, an analysis of benign radiation-induced strictures characterised their incidence after radical radiotherapy at median doses of 60 Gy (range 50–70 Gy), providing important data for patient counselling in definitive treatment intent.^[7]

Radio-chemo-immunotherapy in gastric cancer – the MIRACLE-G study

The MIRACLE-G prospective single-arm phase II study (presented as Digital Poster Highlight) reported preliminary efficacy and safety results of combined radiotherapy and chemoimmunotherapy in GC patients with limited nodal metastases. Eligible patients (n=12) received hypofractionated radiotherapy followed by SOX/FOLFOX chemotherapy, PD-1 inhibitor (with trastuzumab added for HER-2 positive patients). ORR was 91.7% (11/12). Among the 9 patients who underwent radical surgery, the R0 resection rate was 100% (9/9), and a high pCR rate of 66.7% (6/9) was achieved. No grade 5 toxicity was observed; the most frequent grade 3/4-grade TRAEs were lymphocytopenia (25%%), thrombocytopenia (17%), and anaemia (8.3%). These results show promising efficacy and a manageable safety profile.

[ref] Zhou M, et al. Radiotherapy combined with chemoimmunotherapy in gastric cancer with limited lymph node metastases: Preliminary results of the MIRACLE-G study. Abstract Book Part I (Digital Poster Highlight 789). Radiother. Oncol. 2026;218(Suppl 1).

SBRT on MR-Linac — Progressive Margin Reduction

The most technically innovative pancreatic abstract described progressive PTV margin reduction for pancreatic SBRT on an MR-linac using Comprehensive Motion Management (CMM) with intrafraction tracking and gating. Median beam-on time was 12 minutes and 35 seconds, with a mean of 55.4 beam-hold instances per fraction; 39 baseline-shift re-plans were required for persistent target drift. This workflow establishes the MR-linac as a precision instrument for pancreatic SBRT margin reduction, with implications for sparing of adjacent duodenum and bowel.^[8]

SBRT in Elderly and Recurrent Disease

Two further poster abstracts addressed underexplored clinical contexts. SBRT in elderly patients with borderline resectable or locally advanced pancreatic cancer was shown to be feasible with an acceptable toxicity profile,^[9] supporting the applicability of stereotactic approaches across age groups. A further study from the Florence group investigated SBRT for isolated local recurrence after prior resection, presenting early feasibility data and pathological response rates — a setting of growing interest as systemic therapy improves distant disease control and local relapse becomes the dominant failure pattern.^[10]

TACE → SBRT → Dual Checkpoint Inhibition (Phase II)

A phase II trial from the University of Hong Kong combined sequential TACE, SBRT, and dual immunotherapy (Durvalumab + Tremelimumab) in locally advanced HCC, using 67.5 Gy RBE/15 fractions for peripheral tumours (n=20) and 58.0 Gy RBE for central tumours (n=28). No treatment-related deaths occurred within 4 months. RILD occurred in 6.3% overall (all in the central group, 11.5%); grade 3–4 toxicity was substantially higher in the central group (69.2 vs. 4.5 events per 100 patients). This multi-modal platform — ablative RT as an immunostimulatory bridge — represents a major conceptual advance and warrants further prospective evaluation, while mandating caution regarding central tumour localisation.^[11]

National Phase II Proton Therapy Trial

Short-term safety data of a national phase II study (NCT05203120) of hypofractionated proton therapy in HCC used the same dose groups as above. The primary safety endpoint (treatment-related death or RILD within 4 months) was not reached in any peripheral-tumour patient; RILD occurred in 11.5% of central tumour patients, identifying central localisation as the dominant risk factor for radiation-induced hepatotoxicity.^[12]

Long-Term Real-World SBRT Data

A 10-year real-world analysis from Humanitas Milan demonstrated excellent outcomes of SBRT in HCC: 2-year OS 82%, 2-year local control 100%, and an RILD rate of 0% in a predominantly Child-Pugh A cohort.^[13] Complementary institutional data^[14] and MR-guided SBRT outcomes^[15] (2-year local control 89.7%) consolidate the body of evidence supporting SBRT as highly effective for HCC across platforms and geographies.

Oligoprogression Strategy

A prospective multicentre study (10 centres, n=36) investigated progression-directed radiotherapy (PDRT) combined with continued first-line systemic therapy (FLST) in oligo-progressive HCC. With a median follow-up of 10.9 months, the approach demonstrated a median PFS of 7.0 months (95% CI 4.9–9.7), positioning PDRT as a 'line 1.5' strategy to bridge between first- and second-line systemic therapy — a concept with direct relevance for future adaptive systemic-RT combination trial design in HCC.^[16]

Gallbladder Cancer — First RCT of NACRT vs. NACT

The first prospective randomised trial comparing neoadjuvant chemoradiotherapy (NACRT: 50.4 Gy/28 fractions IMRT + weekly gemcitabine) with neoadjuvant chemotherapy (NACT: gemcitabine/cisplatin ×6 cycles) in unresectable locally advanced gallbladder cancer demonstrated marked superiority of NACRT in complete response (46.2% vs. 8.3%) and partial response (53.8% vs. 33.3%), with stable and progressive disease occurring exclusively in the NACT group (58.3%; p=0.003). Median OS was 14.16 vs. 10.46 months in favour of NACRT (p=0.03). Quality of life (FACT-G, T-FACT-Hep) also favoured NACRT. Although the R0-resection rate was comparable (≈16% per group), this trial provides the first randomised evidence that NACRT outperforms chemotherapy alone in this aggressive malignancy.^[17]

Cholangiocarcinoma — ABC-07 Post-Hoc Analysis

A post-hoc analysis of the ABC-07 trial (SBRT + systemic therapy for locally advanced CCA) from UCL London examined the role of hepatobiliary infections and liver function deterioration as outcome modifiers. A rise in ALBI score (GALBI >0) was independently predictive of worse OS (p=0.03); 55% of ALBI rises occurred during chemotherapy. Critically, mean liver dose-BED did not differ between patients with or without infections (34.9 vs. 29.7 Gy; p=0.3) or by GALBI group (32.8 vs. 32.5 Gy; p=0.95), demonstrating that liver toxicity in this setting is driven by infection and disease-related liver deterioration rather than radiation dose. These findings have direct implications for patient selection, stratification, and supportive care protocols in future SBRT trials for CCA.^[18]

SBRT Target Coverage Modelling

A predictive model for SBRT target coverage in unresectable intrahepatic CCA demonstrated a 1-year local control rate of 96%, with disease progression in 13% of lesions, providing a framework for individualised dose prescription and plan evaluation relevant to prospective CCA SBRT trial design.^[19]

Institutional and registry data continue to consolidate SBRT as the standard ablative modality for liver oligometastases. A 10-year institutional series reported a 1-year local control rate of 95%.^[20] MR-guided SBRT data demonstrated 2-year local control of 89.7% across liver metastases and HCC combined.^[15] These results are consistent with mature SBRT literature and support the expanding use of ablative RT in this setting.

SABR-5 Five-Year Follow-Up

The 5-year follow-up of the SABR-5 trial (n=380; median follow-up 54.2 months) provides the most mature safety dataset for stereotactic ablative radiotherapy in oligometastatic disease. GI primaries accounted for 17% of patients (predominantly colorectal cancer, approximately 65 patients). After 5 years, grade 2 toxicity was 18.4%, grade 3 5.8%, and no grade 4 events were recorded; there was one late grade 5 event in a patient treated near hepatobiliary structures. Nausea (0.5% grade ≥3), predominantly in abdominal/hepatic SABR, was the principal GI-specific toxicity. These data confirm the favourable long-term safety profile of ablative RT across oligometastatic histologies, including GI primaries.^[21]

OligoCare Registry and Predictors of Local Control

The ESTRO-EORTC E2-RADIatE OligoCare registry interim analysis identified clinical and treatment predictors of local control following SBRT in a prospective observational cohort, with colorectal cancer as an explicitly enrolled subgroup.^[22] Separately, a large-scale analysis confirmed that higher BED (HR 0.996; p=0.018) was the dominant independent predictor of local control across oligometastatic histologies, which is of direct relevance to dose prescription decisions in liver and other GI site metastases.^[23]

Authors

ESTRO Upper GI Focus Group
 

Thomas Brunner
Chair ESTRO Upper GI Focus Group
Radiation Oncologist
Medical University of Graz, Graz, Austria

Francesco Cellini
Radiation Oncologist
Fondazione Policlinico Universitario A. Gemelli IRCCS 
Rome, Italy

Peter van Rossum
Radiation Oncologist
Amsterdam UMC, Amsterdam, The Netherlands

Tiuri Kroese
Radiation Oncologist
University Hospital Zurich, Zurich, Switzerland

 Eleni Gkika
Radiation Oncologist
University Hospital Bonn, Bonn, Germany

Marcel Verheij
Radiation Oncologist
Radboud University Medical Center, Nijmegen, The Netherlands

Eva Versteijne
Radiation Oncologist
Amsterdam UMC, Amsterdam, The Netherlands

Paul Rogowski
Radiation Oncologist
LMU Munich, Munich, Germany

Siyer Roohani
Radiation Oncologist
University Medical Center Hamburg-Eppendorf, Hamburg, Germany

Florence Huguet
Radiation Oncologist
Assistance Publique - Hôpitaux de Paris, Sorbonne Université Paris 
Paris, France

[1] Bachmann N, et al. ARTEC Trial. [A1] Preliminary results from the ARTEC trial: prospective single-center study of online adaptive radiotherapy (oART) for esophageal cancer on the ETHOS platform. ESTRO 2026 Abstract Book Part I (Proffered Paper). Radiother Oncol. 2026;218(Suppl 1).

[2] Wu JY, Su CYE, et al. The Burden of Radiotherapy on Future Vascular Risk in Esophageal Cancer: A Real-World Evidence Study. ESTRO 2026 Abstract #1873. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[3] [Author(s)]. Temporal heart dose variations during IMPT for esophageal cancer and the impact of an adaptation protocol. ESTRO 2026 Abstract #2836. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[4] Çiflik N, et al. Radiation-induced lymphopenia during neoadjuvant chemoradiotherapy as predictive biomarker for nivolumab benefit in esophageal cancer. ESTRO 2026 Abstract #4899. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[5] Wang Q, et al. A Study on Preoperative pCR Prediction in Esophageal Cancer Using Longitudinal CT Images and Chain-of-Thought Prompt Learning. ESTRO 2026 Abstract #182. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[6] Stanescu T, Hosni A, Lukovic J, et al. Strategy for Esophageal Cancer Using Conventional Delivery and an MR-Linac Adaptive Boost. ESTRO 2026 Abstract #4208. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[7] Kapacee ZA, et al. Characterising Benign Radiation-Induced Strictures After Radical Radiotherapy for Oesophageal Cancer. ESTRO 2026 Abstract #2452. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[8] Rigo M, De-Colle C, Giaj-Levra N, et al. Progressive margin reduction in Pancreas SBRT on MR-Linac with target intrafraction tracking and gating using Comprehensive Motion Management (CMM). ESTRO 2026 Abstract #3209. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[9] [Author(s)]. Feasibility and Safety of SBRT in Elderly Patients With Borderline or Locally Advanced Pancreatic Cancer. ESTRO 2026 Abstract #2867. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[10] Loi M, Aquilano M, et al. Stereotactic Body Radiotherapy for Isolated Local Recurrence from Pancreatic Cancer. ESTRO 2026 Abstract #3357. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[11] Chiang CL, et al. Sequential TACE, SBRT, and Anti-PD-L1 plus Anti-CTLA-4 Immunotherapy in Locally Advanced Hepatocellular Carcinoma: Survival Outcome of Phase II Trial. ESTRO 2026 Abstract #2260 (Proffered Paper). Radiother Oncol. 2026;218(Suppl 1):S[xx].

[12] [Author(s)]. A National Phase II Study of Proton Therapy in Hepatocellular Carcinoma: Short-Term Safety Data (NCT05203120). ESTRO 2026 Abstract #3981 (Proffered Paper). Radiother Oncol. 2026;218(Suppl 1):S[xx].

[13] Vernier V, Comito T, et al. Ten-year real-world analysis of SBRT in the management of hepatocellular carcinoma. ESTRO 2026 Abstract #3169. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[14] [Author(s)]. Real-World Outcomes of Patients with Hepatocellular Carcinoma (HCC) Treated with Liver Stereotactic Ablative Radiotherapy (SBRT). ESTRO 2026 Abstract #3418. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[15] [Author(s)]. Local control and clinical outcomes of MR-guided SBRT for liver metastases and hepatocellular carcinoma: institutional experience. ESTRO 2026 Abstract #3364. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[16] [Author(s)]. Progression-directed radiotherapy (PDRT) combined with ongoing first-line systemic therapy in oligoprogressive HCC. ESTRO 2026 Abstract (Proffered Paper, Oligometastatic Session). Radiother Oncol. 2026;218(Suppl 1):S[xx].

[17] Thakur S, Vias P, Chand B. A prospective randomised trial to evaluate radiological response and surgical downstaging after NACRT versus NACT in unresectable gallbladder cancer. ESTRO 2026 Abstract #1852 (Proffered Paper). Radiother Oncol. 2026;218(Suppl 1):S[xx].

[18] Zhang Y, Brand D, Bridgewater J, Hawkins MA. Hepatobiliary infections and liver-function deterioration impact survival in locally advanced cholangiocarcinoma: post-hoc analysis of ABC-07 trial. ESTRO 2026 Abstract #2149 (Proffered Paper). Radiother Oncol. 2026;218(Suppl 1):S[xx].

[19] [Author(s)]. Predictive model for SBRT target coverage in unresectable intrahepatic cholangiocarcinoma. ESTRO 2026 Abstract #4794. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[20] Catalo M, Gomes D, et al. Liver SBRT in oligometastatic disease: 10 years of institutional experience. ESTRO 2026 Abstract #3499. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[21] Olson RA, et al. Five-Year Follow-Up of the SABR 5 Trial: Primary Toxicity Analysis of Stereotactic Ablative Radiotherapy for Up to Five Oligometastases. ESTRO 2026 Abstract #2328 (Proffered Paper). Radiother Oncol. 2026;218(Suppl 1):S[xx].

[22] Ricardi U, Scorsetti M, Alongi F, et al. Clinical and treatment characteristics associated with local control following SBRT: interim analysis of ESTRO EORTC E2-RADIatE OligoCare cohort. ESTRO 2026 Abstract #2986. Radiother Oncol. 2026;218(Suppl 1):S[xx].

[23] Marini B, Franceschini D, Marco A, et al. Predictors of Local Control after SBRT for Oligometastatic Cancer: A Large-Scale Analysis. ESTRO 2026 Abstract #4997. Radiother Oncol. 2026;218(Suppl 1):S[xx].

Note: Page numbers (S[xx]) refer to the supplement pagination of Radiotherapy & Oncology Vol. 218, Suppl. 1, 2026 and should be verified against the final published abstract book.