Influence of different post-contrast time points on dynamic contrast-enhanced (DCE) MRI T staging in breast cancer.

Purpose: to assess whether MRI T stage of breast cancer lesions (BCLs) is affected by maximum diameter (MD) measured at different post-contrast time points (TPs) on different acquisition planes on dynamic contrast-enhanced (DCE) MRI sequence.

Methods: 53 DCE-MRI examinations of patients with BCLs were retrospectively selected. MD of BCLs was measured on axial, coronal and sagittal planes on DCE images at five different post-contrast TPs. Friedman test followed by Bonferroni-adjusted Wilcoxon-signed rank test for post-hoc analysis was performed to evaluate differences among the five measurements. Reliability of the measurements was evaluated with the intraclass correlation coefficient analysis. Differences between pathological and MRI T stage assessed at each TP on each acquisition plane were assessed using the Wilcoxon-sign rank test; p values <0.05 were considered statistically significant.

Results: on axial, coronal and sagittal planes, MD measured at TP1 was significantly different (p < 0.0001) compared to those obtained at the subsequent TPs. No significant differences were found between MD measured at TPs 3, 4 and 5. Intra and inter-observer reliability resulted as very good, with ICC ranging between 0.915-0.992 and 0.845-0.911, respectively. MRI T stage assessed at TP1 on axial and sagittal plane as well as at all TPs on coronal plane was significantly different from pathological T stage.

Conclusion: MRI T stage definition of BCLs is significantly affected by the TP used for lesions' MD measurement. TPs 3, 4 and 5 are the preferred TPs for the assessment of MRI T stage of BCLs on both axial and sagittal planes.