Abstract P1-02-02: Usefulness of PET/MRI in predicting complete response in breast cancer patients treated with neoadjuvant chemotherapy
Authors: Sekine Chikako 
Published: March 2020

Abstract
Purpose
Neoadjuvant chemotherapy (NAC) is well established treatment for early breast cancer to enable breast conserving surgery by reducing the tumor size and evaluate real time sensitivity to therapy. Accurate prediction of therapeutic effects is important for treatment management. PET/MRI is a new multi-modality imaging that enables to combine metabolic analysis with PET and morphologic and vascularity analysis with contrast-enhanced MRI. The purpose of this study was to evaluate the utility of PET/MRI in predicting pathological complete response (pCR) to NAC.
Materials and methods
Seventy-four patients underwent PET/MRI, mammography (MG) including tomosynthesis, and ultrasound (US) after NAC. Fifty-nine patients also underwent the same examinations before NAC, while fifteen patients underwent MRI, MG and US before NAC. Regarding PET/MRI, the images were organized from whole-body scans after intravenous injection of 18F-FDG followed by a resting period of 60 min and dynamic contrast enhanced breast MR images with late phase of PET images after 80 min. We predicted complete response (CR) using each modality and compared with pCR. In terms of PET/MRI, disappearance of FDG uptake and no enhanced lesions with contrast enhanced MRI were defined as CR. In MG and US, undetectable lesions were defined as CR. The only residual calcification represented on MG cases were considered CR. pCR was defined as when there were no residual invasive cancer cells. Patients’ background and tumor characteristics were also analyzed between pCR and non-pCR cases.
Results
Of the 74 patients enrolled in this study, 18 (24.3%) achieved pCR. The overall sensitivity and specificity of each modality was 70.6% and 80.4% for MG, 16.7% and 91.1% for US, and 72.2% and 78.6% for PET/MRI. The sensitivity and specificity of each modality according to the positivity of hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) were summarized in Table1. Both the sensitivity in HR positive cases and the specificity in HR negative cases at PET/MRI were 100%. According to the results, HR negative and HER2 positive cases demonstrated a significant correlation with pCR compared with HR positive cases and triple negative cases (p=0.017). Furthermore, “mass” type lesions with MRI before NAC demonstrated as pCR with a higher frequency compared with “non-mass” type lesion. There was a statistical significant difference between the two (p=0.018).
Conclusion
PET/MRI enabled to conduct different diagnostic approaches with a multi-modality system and demonstrated higher diagnostic accuracies of the responses of NAC with reference to hormonal subtypes and morphological subtypes in breast cancer.
Sensitivity (first number) and specificity (second number) for each modality according to subtype.Total (n=74)HR+/HER2-(n=30)HR+/HER2+ (n=16)HR-/HER2+ (n=10)HR-/HER2- (n=18)MG70.6 / 80.466.7 / 81.550.0 / 75.060.0 / 75.0100 / 84.6US16.7 / 91.133.3 / 92.625.0 / 91.7 - / 10020.0 / 84.6PET/MRI72.2 / 78.6100 / 74.1100 / 58.350.0 / 10060.0 / 100
Citation Format: Chikako Sekine. Usefulness of PET/MRI in predicting complete response in breast cancer patients treated with neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-02-02.