Comparing Abbreviated and Full MRI Protocols for Preoperative Local Staging of Locally Advanced Rectal Cancer.

Rationale and objectives: This study aimed to compare the diagnostic accuracy of the abbreviated MRI protocol (AP) with the full protocol (FP) in preoperative staging of locally advanced rectal cancer (LARC).

Materials and methods: This prospective single-center study included 131 cases of LARC. All patients underwent the FP rectal MRI, including T2-weighted imaging (T2WI) and contrast-enhanced T1WI, as well as the AP MRI, which included only T2WI. Two independent readers with 10 and 15years of experience in gastrointestinal imaging evaluated all MRI images for both protocols. The interpretation time for each protocol was compared using the Wilcoxon Signed-Rank test. Diagnostic accuracy in predicting tumor stage, mesorectal fascia (MRF) involvement, and extramural venous invasion (EMVI) was assessed using histopathology as the reference standard. The inter-test agreement was evaluated using Cohen's Kappa test.

Results: The AP protocol showed a sensitivity of 82.1%, specificity of 95.3%, and accuracy of 94.4%. In comparison, the FP protocol demonstrated a sensitivity of 91%, specificity of 100%, and accuracy of 97.6% for the local staging of LARC. There was strong agreement between both protocols in T staging, MRF involvement, and EMVI detection, with Cohen's kappa (K) values of 0.862, 0.710, and 0.863, respectively. The median interpretation time for the AP and FP protocols was 12 and 22 minutes, respectively. Moreover, the AP had a significantly shorter interpretation time than the FP (P<.001).

Conclusion: The AP demonstrated high diagnostic performance with significantly reduced interpretation time, suggesting its potential as an alternative in certain clinical settings.