To compare hyperpolarized carbon 13 (¹³C) MRI with dynamic contrast material–enhanced (DCE) MRI in the detection of early treatment response in breast cancer.

In this institutional review board–approved prospective study, a woman with triple-negative breast cancer (age, 49 years) underwent ¹³C MRI after injection of hyperpolarized [1–carbon 13 {¹³C}]-pyruvate and DCE MRI at 3 T at baseline and after one cycle of neoadjuvant therapy. The ¹³C-labeled lactate-to-pyruvate ratio derived from hyperpolarized ¹³C MRI and the pharmacokinetic parameters transfer constant (K^trans) and washout parameter (k_ep) derived from DCE MRI were compared before and after treatment.

Exchange of the ¹³C label between injected hyperpolarized [1-¹³C]-pyruvate and the endogenous lactate pool was observed, catalyzed by the enzyme lactate dehydrogenase. After one cycle of neoadjuvant chemotherapy, a 34% reduction in the ¹³C-labeled lactate-to-pyruvate ratio resulted in correct identification of the patient as a responder to therapy, which was subsequently confirmed via a complete pathologic response. However, DCE MRI showed an increase in mean K^trans (132%) and mean k_ep (31%), which could be incorrectly interpreted as a poor response to treatment.

Hyperpolarized ¹³C MRI enabled successful identification of breast cancer response after one cycle of neoadjuvant chemotherapy and may improve response prediction when used in conjunction with multiparametric proton MRI.

Keywords: Breast, MR-Spectroscopy, Molecular Imaging-Cancer, Molecular Imaging-Clinical Translation, Neoplasms-Primary, Oncology, Tumor Response

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