ESTRO 2025 - Abstract Book

S962

Clinical – Head & neck

ESTRO 2025

Material/Methods: Following PRISMA guidelines 2 , we conducted a systematic review of original studies that assess tumor response during definitive radiotherapy for head and neck cancers. Eligibility criteria included full-length studies on human patients undergoing definitive radiotherapy for head and neck cancers, where treatment response was evaluated using data collected during the course of radiotherapy. Studies were required to correlate in-treatment tumor response with outcomes measured more than two weeks post-treatment, such as loco-regional recurrence, progression-free survival or overall survival. We performed a comprehensive literature search in Medline, Embase, and Web of Science databases. Two independent reviewers screened abstracts and full texts, resolving conflicts with a third reviewer. Nine studies provided data on overall survival stratified by SUVmax from interim FDG PET scans, and hazard ratios from these studies were extracted for meta-analysis. Meta-analysis and forest plot creation, was conducted using Review Manager 5.4 3 . Results: Ninety studies involving 6698 patients met inclusion criteria, involving 16 different modalities for response evaluation (tabel 1). FDG-PET was the most frequently studied modality (32 studies, 1219 patients), followed by MRI (30 studies, 926 patients) and CT (12 studies, 1295 patients). Response assessment was most commonly performed in the third week of radiotherapy, but with substantial variation. Meta-analysis of studies stratifying overall survival by SUVmax on interim FDG PET yielded a statistically significant hazard ratio of 2.74 [1.65, 4.57] (Higher SUV vs lower) with moderate heterogeneity (I² = 34%) among included studies. Conclusion: A large body of literature aim to predict tumor response during radiotherapy, primarily using MRI and FDG-PET during week 3. Meta-analysis indicates that higher SUVmax values on interim FDG PET are associated with poorer overall survival with an effect size of the same order as HPV status (Interim PET HR=2.7, HPV reported to HR=3.0 4 ). This is encouraging for response evaluation strategies, but there is a need for standardizing method and timing of in-treatment response measurements.

Tabel 1