Changes in hyperpolarized 13C-, but not 1H-MRI–derived metrics, after approximately one week of treatment distinguish responders (pCR) from nonresponders (incomplete response; non-pCR). In the five patients undergoing standard-of-care neoadjuvant treatment, an increase of ≥20% in LAC/PYR was only observed in patients who responded (A), whereas a lower increase or even a decrease in LAC/PYR was observed in nonresponders (B).Both patients treated with a PARP inhibitor in addition showed an increase in LAC/PYR (A and B) and again the increase was highest in the responder (A). Although kPL increased in all patients receiving a PARP inhibitor, but not in the other patients (C and D), neither kPL nor any of the 1H-MRI–based metrics from dynamic contrast-enhanced (DCE) MRI (such as Ktrans) or from intravoxel incoherent motion (IVIM) as part of diffusion-weighted MRI (such as perfusion fraction f and tissue diffusivity D) could distinguish between responders and nonresponders (I–P). None of the parameters differed significantly between baseline and follow-up when evaluated for responders and nonresponders separately (P > 0.05). kPL was not available in one patient due to technical failure (C). Ktrans could not be assessed in one patient due to failed fat saturation (K).