Related Experiment Video
Updated: Sep 6, 2025
Pretargeted Radioimmunotherapy Based on the Inverse Electron Demand Diels-Alder Reaction
Published on: January 29, 2019
Relationship Between Baseline Rectal Tumor Length and Magnetic Resonance Tumor Regression Grade Response to
Nicola Hodges1,2, Nicholas Battersby3, Sheela Rao1
1The Royal Marsden NHS Foundation Trust and Imperial College London, Sutton, UK.
Background:
It is widely believed that small rectal tumors are more likely to have a good response to neoadjuvant treatment, which may influence the selection of patients for a 'watch and wait' strategy.
Objective:
The aim of this study was to investigate whether there is a relationship between baseline tumor length on magnetic resonance imaging (MRI) and response to chemoradiotherapy.
Method:
The 96 patients with locally advanced rectal cancer randomised (2:1-intervention:control) in the TRIGGER feasibility study where eligible. Baseline tumor length was defined as the maximal cranio-caudal length on baseline MRI (mm) and was recorded prospectively at study registration. Magnetic resonance tumor regression grade (mrTRG) assessment was performed on the post-chemoradiotherapy (CRT) MRI 4-6 weeks (no later than 10 weeks) post completion of CRT. This was routinely reported for patients in the intervention (mrTRG-directed management) arm and reported for the purposes of this study by the central radiologist in the control arm patients. Those with an mrTRG I/II response were defined as 'good responders' and those with an mrTRG III-V response were defined as 'poor responders'.
Results:
Overall, 94 patients had a post-CRT MRI performed and were included. Forty-three (46%) patients had a good response (mrTRG I/II) and 51 (54%) patients had a poor response (mrTRG III/IV). The median tumor length of good responders was 43 mm versus 50 mm (p < 0.001), with considerable overlap in tumor lengths between groups.
Conclusion:
Baseline tumor length on MRI is not a clinically useful biomarker to predict mrTRG tumor response to CRT and therefore patient suitability for a deferral of surgery trial.
