Comparison of abbreviated and complete MRI protocols for treatment response assessment of colorectal liver metastases.

Objective: To compare abbreviated magnetic resonance imaging (MRI) to complete MRI for treatment response assessment of colorectal liver metastases.

Material and methods: This retrospective study included consecutive patients with colorectal liver metastases between January 1, 2012, and December 3, 2021, who were undergoing chemotherapy and who had at least one follow-up gadoxetic-enhanced MRI. For each patient, two MRIs (baseline MRI and follow-up MRI) were randomly selected. Follow-up MRIs were separated into two sets of images: complete MRIs, including all imaging sequences, and abbreviated MRIs, including coronal and axial hepatobiliary phase imaging, axial diffusion-weighted imaging, and coronal T2-weighted imaging. Seven radiologists reviewed the two sets of images, with a month's break in between, assessing Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 category and the presence of new lesions, with each reader assigned 80-91 patients. Inter-reader agreement was assessed using Fleiss' kappa (κ).

Results: One-hundred ninety-five patients (mean age 54.4 +/- 12.1 years, 135 men) were evaluated. Intra-reader agreement between abbreviated and complete MRI was substantial for the RECIST 1.1 category (κ, 0.66-0.89) and the detection of new lesions (κ, 0.63-0.81). Inter-reader agreement was substantial for RECIST 1.1 category using abbreviated MRI and complete MRI (κ, 0.71 (95% CI: 0.65-0.78) and 0.68 (95% CI: 0.61-0.75)), and moderate for the presence of new lesions using abbreviated MRI and complete MRI (κ, 0.56 (95% CI: 0.41-0.69) and 0.49 (95% CI: 0.35-0.65)).

Conclusion: Abbreviated MRI may serve as an alternative to complete MRI for the follow-up of patients with colorectal liver metastases.

Key points: Question Abbreviated MRI is a time-saving and cost-effective exam, but only one study has compared it with complete MRI for treatment response assessment of colorectal liver metastases. Findings In our study, abbreviated follow-up MRI achieved substantial inter-reader agreement for the RECIST 1.1 category and moderate inter-reader agreement for the presence of new lesions. Clinical relevance Abbreviated liver MRIs are adequate substitutes for complete liver MRIs for colorectal liver metastases in the follow-up setting when the goal is to assess treatment response, resulting in shorter examination times and potential reductions in costs.