Tumor necrosis by pretreatment breast MRI: association with neoadjuvant systemic therapy (NAST) response in triple-negative breast cancer (TNBC)

Abstract

Purpose: To determine if tumor necrosis by pretreatment breast MRI and its quantitative imaging characteristics are associated with response to NAST in TNBC.

Methods: This retrospective study included 85 TNBC patients (mean age 51.8 ± 13 years) with MRI before NAST and definitive surgery during 2010-2018. Each MRI included T2-weighted, diffusion-weighted (DWI), and dynamic contrast-enhanced (DCE) imaging. For each index carcinoma, total tumor volume including necrosis (TTV), excluding necrosis (TV), and the necrosis-only volume (NV) were segmented on early-phase DCE subtractions and DWI images. NV and %NV were calculated. Percent enhancement on early and late phases of DCE and apparent diffusion coefficient were extracted from TTV, TV, and NV. Association between necrosis with pathological complete response (pCR) was assessed using odds ratio (OR). Multivariable analysis was used to evaluate the prognostic value of necrosis with T stage and nodal status at staging. Mann-Whitney U tests and area under the curve (AUC) were used to assess performance of imaging metrics for discriminating pCR vs non-pCR.

Results: Of 39 patients (46%) with necrosis, 17 had pCR and 22 did not. Necrosis was not associated with pCR (OR, 0.995; 95% confidence interval [CI] 0.4-2.3) and was not an independent prognostic factor when combined with T stage and nodal status at staging (P = 0.46). None of the imaging metrics differed significantly between pCR and non-pCR in patients with necrosis (AUC < 0.6 and P > 0.40).

Conclusion: No significant association was found between necrosis by pretreatment MRI or the quantitative imaging characteristics of tumor necrosis and response to NAST in TNBC.

Keywords: Diffusion-weighted MRI; Multiparametric MRI; Necrosis; Neoadjuvant therapy; Triple-negative breast cancer.

Fig. 1

Inclusion criteria and assignment of analysis for each group. ADC apparent diffusion coefficient, DCE dynamic contrast-enhanced imaging, DWI diffusion-weighted imaging, NAST neoadjuvant systemic therapy, NV necrosis-only volume, PE percent enhancement, T2WI T2-weighted imaging, TNBC triple-negative breast cancer, TTV total tumor volume including necrosis, TV tumor volume without necrosis

Fig. 2

Necrosis in a 35-year-old woman with TNBC of the left breast. a Axial fat-suppressed early-phase dynamic contrast-enhanced image shows central non-enhancing area representing necrosis (arrow). b Axial fat-suppressed T2-weighted image shows necrosis as central area of high signal intensity (arrow). c Axial apparent diffusion coefficient map shows shine-through corresponding to central area of necrosis (arrow) seen on dynamic contrast-enhanced and T2-weighted imaging

Fig. 3

Segmentation technique in a 60-year-old woman with TNBC of the right breast. Axial dynamic contrast-enhanced early-phase fat-suppressed images with whole tumor (a), tumor without necrosis (b), and necrosis-only (c) segmentations, as well as corresponding apparent diffusion coefficient maps (d, e, f)

Fig. 4

Necrotic index carcinoma with a pathological complete response after neoadjuvant systemic therapy in a 46-year-old woman with TNBC of the right breast. The volume of necrotic material was 10 cm³, and the percent of the total tumor volume occupied by necrosis was 17%. a Axial fat-suppressed early-phase dynamic contrast-enhanced image shows central non-enhancing area representing necrosis (arrow). b Axial fat-suppressed T2-weighted image shows necrosis as central area of high signal intensity (arrow). c Axial apparent diffusion coefficient map shows shine-through corresponding to the central area of necrosis (arrow)

Fig. 5

Necrotic index carcinoma with pathological non-complete response after neoadjuvant systemic therapy in a 30-year-old woman with TNBC of the left breast. The volume of necrotic material was 4 cm³, and the percent of the total tumor volume occupied by necrosis was 17%. a Axial fat-suppressed early-phase dynamic contrast-enhanced image shows central non-enhancing area representing necrosis (arrow). b Axial fat-suppressed T2-weighted image shows necrosis as a central area of high signal intensity (arrow). c Axial apparent diffusion coefficient map shows shine-through corresponding to central area of necrosis (arrow)

Fig. 6

Clustering of necrosis volume or NV_DCE (a) and necrosis-only volume as a percent of total tumor volume or %NV_DCE (b), by dynamic contrast-enhanced MRI associated with response to neoadjuvant systemic therapy. There is no difference between TNBC patients with and without pathologic complete response (pCR)