MRI prognostic features in rectal cancer neoadjuvant trials: A systematic review of reporting gaps across two decades

Magnetic resonance imaging (MRI) is central to staging and treatment planning in rectal cancer, particularly in identifying candidates for neoadjuvant therapy. Prognostic MRI features such as tumour depth (mrT), extramural venous invasion (EMVI) and tumour deposits (TDs) are increasingly recognised as markers of systemic risk, yet their reporting in randomised controlled trials (RCTs) remains unclear. This systematic review aimed to evaluate the reporting frequency, consistency and integration of pre-treatment MRI prognostic variables in RCTs assessing neoadjuvant treatment for rectal cancer.

A systematic search was conducted across MEDLINE, EMBASE, Web of Science and CENTRAL from 01 January 2005 to 18 November 2025. RCTs evaluating neoadjuvant strategies in adult patients with resectable rectal cancer were included. Two reviewers independently extracted data on MRI variables, protocol details and trial design. PRISMA guidelines were followed.

Of 1,283 screened studies, 34 RCTs met inclusion criteria. All studies reported mrT, and 33 (97%) included nodal staging (mrN). mrEMVI was reported in only 10 trials (29.4%), and mrT substage was reported in 5 studies (14.7%). MRI protocols were inconsistently described, with only 5 trials specifying acquisition parameters. Only 10 studies incorporated EMVI into risk stratification frameworks. Four trials did not mandate MRI for baseline staging.

Despite MRI's critical role in rectal cancer management, key prognostic features such as EMVI/TDs and mrT substage are underreported. This omission risks poor risk stratification, trial imbalance and misinformed clinical guidance. Standardisation of MRI reporting is urgently needed to enhance trial validity and optimise personalised treatment strategies.