6P - Effect of apparent diffusion coefficient in predicting pathologic responses in patients with breast cancer treated with neoadjuvant chemotherapy using nanoparticle albumin-bound paclitaxel

Background

Neoadjuvant chemotherapy (NAC) results in a pathologic complete response (pCR) and is associated with disease-free survival and overall survival. The apparent diffusion coefficient (ADC) indicates the stability of water molecules and is used to predict the response of solid tumors to chemotherapy. Therefore, we evaluated the changes in ADC using diffusion-weighted breast magnetic resonance imaging (MRI) to predict pCR in patients with breast cancer treated with NAC.

Methods

From August 2013 to April 2019, 50 patients (mean age, 55 years; age range, 31–75 years) were treated with nanoparticle albumin-bound paclitaxel (nab-PTX) (260 mg/m²) every 3 weeks for four cycles ± concurrent trastuzumab (8 mg, 6 mg/kg) every 3 weeks for four cycles in human epidermal growth factor receptor 2 (HER2)-positive patients followed by FEC (5-fluorouracil/epirubicin/cyclophosphamide, 500/100/500 mg/m²) every 3 weeks for four cycles. pCR was defined as the absence of any residual invasive cancer or ductal carcinoma in situ in the breast. Changes in ADC (Δnab-PTX: post nab-PTX – pre nab-PTX, ΔFEC: post FEC – pre nab-PTX) were also calculated.

Results

The tumor phenotypes were triple negative (TN) (n = 25) and HER2 positive (n = 25). pCR was achieved in 27 patients [54%] (11 with TN disease and 16 with HER2-positive disease). The mean pre nab-PTX ADC and ΔFEC ADC in pCR patients were 0.718±0.157 × 10^-3 mm² and 0.621±0.357 × 10^-3 mm², respectively, and they were not associated with pCR (p = 0.06 and p = 0.248, respectively). However, the mean post nab-PTX ADC and Δnab-PTX ADC were 1.117±0.303 × 10^-3 mm² and 0.400±0.311 × 10^-3 mm², respectively, and they were associated with pCR (p < 0.01 and p = 0.01, respectively). Using receiver operating characteristic (ROC) analysis with Δnab-PTX ADC, the area under the curve was 0.691 [95% confidence interval: 0.54–0.841] in all patients. Δnab-PTX ADC and pCR were significantly correlated (p = 0.00463).

Conclusions

High Δnab-PTX ADCs in diffusion-weighted breast MRI may be promising findings for the successful prediction of pCR in patients treated with NAC using nab-PTX followed by FEC.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The author.

Funding

Has not received any funding.

Disclosure

The author has declared no conflicts of interest.