ESTRO 2025 - Abstract Book

S1762

Clinical – Upper GI

ESTRO 2025

reactive, low dose/fractionation RT for symptoms with minimal RCT evidence to support pre-emptive, high dose RT. 1 GastroSCOPE will evaluate the latter. Patient and clinician involvement was integral to trial development.

Material/Methods: Clinicians and patient representatives informed trial design via: • Online survey of UK oesophago-gastric oncologists exploring perception of gastric RT and interest in future RCTs 2 • Further clinician surveys gathering feedback on trial design and expressions of interest (EOI) • Presentation at national meetings and dedicated research groups • Involvement of three (PPI) research partners at all stages from inception • Two online patient focus groups including patients, carers and experienced PPI contributors (presentation followed by facilitated discussion/questions around key themes).

Results:

Proposed trial schema adds RT to best available SACT, was developed following literature review 3 , clinician surveys and PPI feedback (Figure 1). Three distinct cohorts (A, B, C), covering a range of clinical presentations were included, maximising trial accessibility for patients and efficient use of resources. Clinician survey showed 88.9%, 100% and 85% supported design of cohorts A, B and C respectively. 92.5% agreed with 40Gy/15# in A, hypofractionated regimen that aligns with maintenance SACT, reduces treatment time and NHS/environmental burden, whilst maintaining high BED (BED 10 =50.7Gy). For poorer prognosis groups (B,C) a shorter, lower BED (BED 10 =37.5 Gy) fractionation of 25Gy/5# aims to minimise toxicity and treatment burden, with 100% and 95% clinician support respectively. Surveyed clinicians were divided on ‘sandwich’ (45.5%) or consolidation SACT (50.9%), with availability of evidence for the latter being decisive factor for cohorts A and C. 4,5 Both clinician and PPI input informed outcome measures; primary outcome PFS in cohorts A and C, secondary outcomes of quality of life, toxicity and incidence of stomach-related events – the latter being the primary outcome of cohort B.