The TRIGGER Feasibility Trial

Magnetic Resonance Tumour Regression Grade (mrTRG) as a Novel Biomarker to Stratify Management of Good And Poor Responders to Chemoradiotherapy: A Rectal Cancer Multicentre Randomised Control Trial


The response to preoperative chemoradiotherapy (CRT) in rectal cancer patients is highly variable; up to 30% of patients will achieve a complete or near complete response, and the remainder do not respond sufficiently to survive the disease to the same extent. Although the need for a validated means of pre-operative assessing response to treatment is widely accepted, there has been no reliable method of assessing this response pre-operatively and therefore the current standard of care advocates using the baseline MRI as the reference for the plane of surgery regardless of any assessment of treatment response. Recently, an MRI based tumour regression grade has been developed (mrTRG). Patients with a poor CRT response (mrTRG4&5) have a 5-year overall survival of 27% versus 72% (p=0.001) for a good CRT response (mrTRG1-3). This novel imaging biomarker has been reliable and reproducible between multiple independent radiologists. These findings are encouraging, as it appears that the subgroup of mrTRG 1-2 have a significant chance of complete long-term tumour regression. Although validation of this as a biomarker has been based on prospective evaluation of MRI scans against both pathology and survival outcomes, there is insufficient evidence that this information can be used to alter current treatment decisions.


The main objectives of the feasibility trial are to establish the safety and feasibility of recruitment for a larger phase III study. Should feasibility be confirmed then the primary objective of the Phase III trial is to evaluate disease-free survival at 3 years in patients with locally advanced rectal cancer by using mrTRG directed management to selectively offer surgery and additional pre-operative chemotherapy.

The TRIGGER trial is open to new sites.

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