Assessment of diffusion-weighted MRI in predicting response to neoadjuvant chemotherapy in breast cancer patients

Abstract

To compare region of interest (ROI)-apparent diffusion coefficient (ADC) on diffusion-weighted imaging (DWI) measurements and Ki-67 proliferation index before and after neoadjuvant chemotherapy (NACT) for breast cancer. 55 women were enrolled in this prospective single-center study, with a final population of 47 women (49 cases of invasive breast cancer). ROI-ADC measurements were obtained on MRI before and after NACT and were compared to histological findings, including the Ki-67 index in the whole study population and in subgroups of "pathologic complete response" (pCR) and non-pCR. Nineteen percent of women experienced pCR. There was a significant inverse correlation between Ki-67 index and ROI-ADC before NACT (r = - 0.443, p = 0.001) and after NACT (r = - 0.614, p < 0.001). The mean Ki-67 index decreased from 45.8% before NACT to 18.0% after NACT (p < 0.001), whereas the mean ROI-ADC increased from 0.883 × 10^-3 mm²/s before NACT to 1.533 × 10^-3 mm²/s after NACT (p < 0.001). The model for the prediction of Ki67 index variations included patient age, hormonal receptor status, human epidermal growth factor receptor 2 status, Scarff-Bloom-Richardson grade 2, and ROI-ADC variations (p = 0.006). After NACT, a significant increase in breast cancer ROI-ADC on diffusion-weighted imaging was observed and a significant decrease in the Ki-67 index was predicted. Clinical trial registration number: clinicaltrial.gov NCT02798484, date: 14/06/2016.

Figure 1

Illustration of the study protocol.

Figure 2

Images of a 61-year-old woman who received neoadjuvant chemotherapy (NACT) for grade 3 hormone receptor–negative/human epidermal growth factor receptor–positive cancer of the left breast. The patient had residual disease at surgery and therefore did not experience pCR (RCB class: II). Before NACT: physical examination findings showing a large skin ulceration (cT4bN1) (a), axial DCE T1-WI showing a large, irregular, and heterogeneous mass of size 5.75 cm in LD (b), axial DWI showing a high signal intensity mass at b = 800 (c) and an ROI-ADC value of 0.991 × 10^–3 mm²/s placed on the darkest part of the ADC map (d), HE staining of core needle biopsy showing an IDC SBR3 (e). IHC of the core needle biopsy showing nuclear positivity for a Ki-67 proliferation index of 30% (f). After NACT: cicatrization of the skin ulceration (ycT2N0) (g), axial DCE T1-WI showing a residual mass of size 2.72 cm in LD corresponding to a partial response (decrease of 52.7% in LD) (h), axial DWI showing a residual high-signal-intensity mass at b = 800 (i), and an ROI-ADC value of 1.543 × 10^–3 mm²/s placed on the darkest part of the ADC map avoiding clip artifacts (increase of 55.7% in ROI-ADC) (j), HE staining of the surgical specimen showing a residual IDC SBR2 of size 2.2 cm (ypT2N1_(mi), RCB-II) (k), and IHC showing nuclear positivity for a residual Ki-67 proliferation index of 5% (l). ROI region of interest, ADC apparent diffusion coefficient, pCR pathologic response, RCB residual cancer burden, DCE dynamic contrast enhanced, WI weighted imaging, LD largest diameter, DWI diffusion-weighted imaging, HE hematoxylin and eosin, IDC invasive ductal carcinoma, IHC immunohistochemistry.

Figure 3

Changes in the ROI-ADC and Ki-67 index before and after neoadjuvant chemotherapy (NACT) in pathologic complete response (pCR) (a,b) and non-pCR (c,d) patients. ROI region of interest, ADC apparent diffusion coefficient.