Criteria for identifying residual tumours after neoadjuvant chemotherapy of breast cancers: a magnetic resonance imaging study

Abstract

We investigated magnetic resonance imaging (MRI) criteria identifying residual tumours in patients with triple-negative and human epidermal growth factor receptor type 2-positive (HER2+) breast cancer following neoadjuvant chemotherapy. Retrospectively, 290 patients were included who had undergone neoadjuvant chemotherapy and definitive surgery. Clinicopathological features, as well as lesion size and lesion-to-background parenchymal signal enhancement ratio (SER) in early- and late-phase MRIs, were analysed. Receiver operating characteristic (ROC) analyses evaluated diagnostic performances. Maximal MRI values showing over 90% sensitivity and negative predictive value (NPV) were set as cut-off points. Identified MRI criteria were prospectively applied to 13 patients with hormone receptor-negative (HR-) tumours. The lesion size in HR-HER2-tumours had the highest area under the ROC curve value (0.92), whereas this parameter in HR + HER2 + tumours was generally low (≤ 0.75). For HR-tumours, both sensitivity and NPV exceeded the 90% threshold for early size > 0.2 cm (HR-HER2-) or > 0.1 cm (HR-HER2 +), late size > 0.4 cm, and early SER > 1.3. In the prospective pilot cohort, the criteria size and early SER did not find false negative cases, but one case was false negative with late SER. Distinguishing residual tumours based on MRI is feasible in selected triple-negative and HER2 + breast cancer patients.

Figure 1

ROC curves and AUC values for identifying residual lesions. ROC receiver operating characteristic, AUC area under the curve, HR hormone receptor, HER2 human epidermal growth factor receptor 2, SER lesion-to-background parenchymal signal enhancement ratio.

Figure 2

A 44-year-old woman with HR-HER + invasive ductal carcinoma. After 8 cycles of neoadjuvant chemotherapy (NAC, 4 cycles of anthracycline/cyclophosphamide followed by 4 cycles of taxane/trastuzumab), this patient received breast-conserving surgery. A 0.1-cm-sized ductal carcinoma in situ (DCIS) was found in the surgical specimen. a Pre-NAC magnetic resonance imaging (MRI) revealed an irregular enhancing mass in the left breast. b After completion of the NAC, the early post-contrast T1-weighted image showed no enhancing lesion. d In the late phase, a 0.7-cm-sized enhancing lesion was observed at the original tumour site (arrow). c,e are magnified subtraction images of each phase. Lesion-to-background signal enhancement ratios (SERs) were 1.1 in the early phase and 1.3 in the late phase. The presurgical core needle biopsy was diagnosed as atypical apocrine adenosis. According to our definitions of pathological complete response and the preliminary criteria, the MRI findings according to the criteria early size, early SER, and late SER were true negatives. Although the finding according to the criterion late size was a false positive, it may be suggestive of the residual DCIS.

Figure 3

A 33-year-old woman with HR-HER− invasive ductal carcinoma. After 8 cycles of neoadjuvant chemotherapy (NAC, 4 cycles of anthracycline/cyclophosphamide followed by 4 cycles of paclitaxel/cisplatin), this patient received breast-conserving surgery. No residual tumour was found in the surgical specimen. a Pre-NAC magnetic resonance imaging (MRI) showed an irregular enhancing mass in the left breast. b After NAC completion, the early post-contrast T1-weighted image displayed no enhancing lesion around the signal void of an inserted marker clip. d In the late phase, a 1-cm-sized enhancing lesion was observed at the original tumour site (arrow). c,e are magnified subtraction images of each phase. Lesion-to-background signal enhancement ratios (SERs) were 1.3 in the early phase and 1.7 in the late phase. The presurgical core needle biopsy was diagnostic of a fibroadenoma. According to our definitions of pathological complete response and the preliminary criteria, the MRI findings according to the criteria early size and early SER were true negatives, whereas late size and late SER were false positives.