A systematic review examines whether magnetic resonance imaging performed with the patient supine (SMRI) improves the outcomes of breast-conserving surgery in terms of surgical margins and the need for re-excision. The data are promising, but the authors themselves caution that the evidence base is still limited.
What was already known
Achieving negative margins at the first operation is a central goal of breast-conserving surgery, yet positive margins and re-excision remain common. Conventional preoperative MRI is acquired in the prone position, a position the breast does not assume during surgery; the resulting prone-to-supine deformation may degrade image transfer to the operative field. Supine MRI (SMRI) has been proposed to overcome this limitation.
What this work adds
This is a systematic review that evaluated the effect of SMRI on positive surgical margin and re-excision rates in breast-conserving surgery. Four databases were searched from inception to May 2026, with backward citation tracking. Absolute rates were summarised narratively by transfer technique, and a post-hoc exploratory relative-risk meta-analysis was restricted to studies with a comparator. Thirteen studies with 1,718 patients were included.
Main results
Positive margin rates with SMRI ranged from 0% to 25.9%; heterogeneity in margin definitions precluded pooling of absolute rates. Across the five comparative studies, SMRI was associated with a significantly lower risk of a positive margin (relative risk [RR] 0.57; 95% CI: 0.36-0.88) and a non-significant reduction in re-excision (RR 0.64; 95% CI: 0.40-1.04), without detectable heterogeneity. The evidence base was limited: a single randomised trial and 11 of 12 non-randomised studies at serious risk of bias, with baseline confounding that generally disfavoured the intervention.
What it means
The authors conclude that SMRI is a biologically coherent and promising approach that may reduce positive margins, but that current evidence is preliminary and requires randomised comparison against contemporary localisation techniques using harmonised margin definitions. For a patient, this means the technique cannot yet be presented as a consolidated improvement: it is best understood as an open line of research rather than an established standard.
A breast-unit perspective
The relationship between imaging position and surgical position is a practical issue that affects how the surgery and radiology teams of a breast unit plan together. The fact that margin definitions are not harmonised across centres underscores the value of shared reporting protocols and close coordination between specialities.
Reference: Mora H, Cruz D, Gonçalves D, Peleteiro B, Fougo JL. Supine Magnetic Resonance Imaging in Breast-Conserving Surgery Planning: A Systematic Review of Margin and Re-excision Outcomes. Clinical Breast Cancer, 2026. DOI/link
