Ultrafast dynamic contrast-enhanced (DCE)-MRI parameters appear to be associated with breast cancer (BC) aggressiveness. However, the role of ultrafast DCE-MRI parameters as predictive biomarkers for pathological response after neoadjuvant chemotherapy (NAC) has been poorly investigated. To determine whether semiquantitative perfusion parameters calculated on initial ultrafast DCE-MRI are associated with early prediction for pathological response after NAC in patients with BC.

This prospective single-center study included consecutive women with nonmetastatic invasive BC treated with NAC followed by surgery and initial ultrafast DCE-MRI between December 2020 and August 2021. Six semiquantitative ultrafast DCE-MRI parameters were calculated for each patient from the fitted time-signal intensity curve. Multivariable logistic regression identified independent predictors of pathological complete response (pCR) and residual cancer burden (RCB).

Of the 50 women (mean age, 49 years ± 12 [standard deviation]) included, 20 and 25 patients achieved pCR and RCB-0/I, respectively. A wash-in slope (WIS) cut-off value of 1.6%/s had a sensitivity of 94% and a specificity of 59% for pCR. A WIS>1.6%/s (odds ratio [OR] OR=8.4; CI 95%: 1.5, 48; p=.02), HER2 positivity (OR=6.3; CI 95%: 1.5, 27 p=.01) and tumor-infiltrating lymphocytes (TILs)>10% (OR=6.9; CI 95%: 1.3-38; p=.03) were independent predictive factors of pCR. The area under the curve of the three-component model was 0.92 (95% CI: 0.84-0.99). A WIS>1.6% was associated with higher pCR rates in the HER2-positive (OR=22; p=.02) BC subgroups. For luminal HER2-negative BC and triple-negative BC, a WIS>1.6%/s was associated with higher RCB-0/I rates (OR=11; p=.04).

The WIassessment on initial ultrafast DCE-MRI may be used to predict pCR in patientwith BC. The WIvalue identified two subsetof HER2-positive cancerwith distinct pCR rates.

The wash-in slope derived from initial ultrafast dynamic enhanced-contrast MRI may help predict pathologic complete response in patients with breast cancer treated with neoadjuvant therapies before surgery.