Objectives To evaluate the accuracy of Magnetic Resonance Imaging (MRI) in measuring the pure Ductal Carcinoma In Situ (DCIS) size, against pathology, to better understand the MRI role in the management of this non-invasive intraductal breast neoplasm.

Methods Potential eligible studies in MEDLINE, Embase and Google Scholar, until January-2021 were considered, and systematic review and meta-analysis according to the published protocol (Prospero - CRD42021232228) was performed. Outcomes of mean differences and accuracy rates using IBM® SPSS® v26 and random-effect model in platform R v3.3.2 were analysed.

Results Twenty-two cross-sectional studies were selected and 15 proceeded to meta-analyses. MRI accurately predicted 55% of tumours size and according to Bland-Altman plots, concordance between MRI and pathology was greater for smaller tumours. In meta-analyses, the difference of the means between MRI and pathology is 3.85 mm (CI95% [-0.92;8.60]) with considerable heterogeneity (I2=96.7%). Subgroup analyses showed similar effect sizes between different MRI fields, acquisition times and contrasts, but lower heterogeneity in studies using Gadolinium (I2=48.7%) and 3-Tesla MRI (I2=57.2%). Results were concordant in low risk of bias studies (2.46, CI95% [0.57–4.36]), without detected heterogeneity (I2=0%).

Conclusions MRI is an accurate method in pure DCIS size assessment. Once the best MRI protocol is established, evaluation of the impact of pure DCIS size in predicting treatment outcomes will contribute to clarify intraductal breast carcinoma current issues.