Usefulness of interim contrast-enhanced breast MRI for predicting response of breast cancer to neoadjuvant chemotherapy

Abstract Purpose In breast cancer patients, contrast-enhanced breast magnetic resonance imaging (MRI) is usually performed after completing neoadjuvant chemotherapy (NAC) to determine treatment efficacy. We compared the ability of MRI conducted during the interim phase (interim MRI) with that of MRI conducted after NAC (post-NAC MRI) to predict treatment response. Methods In this retrospective study, 260 patients with invasive breast cancer who underwent NAC between April 2010 and December 2020 and who had undergone MRI before, during, and after NAC were included. Most patients received taxane and anthracycline sequentially, while human epidermal growth factor receptor 2 (HER2)-positive cases also received anti-HER2 agents. Results Sixty-five patients (25%) demonstrated a pathological complete response (pCR). The sensitivity and specificity of interim MRI for predicting pCR in all patients were 84% and 83%, respectively, which were comparable with those of post-NAC MRI (88% and 64%, respectively). Its sensitivity and specificity in luminal-type breast cancer were 95% and 50%, respectively, and those in HER2-positive breast cancer were 77% and 73%, respectively, while those in triple-negative breast cancer (TNBC) cases were 94% and 89%, respectively. Twenty-nine (83%) of 35 cases diagnosed with clinical complete response (cCR) by interim MRI achieved pCR, whereas 25 (93%) of the 27 HER2-positive type or TNBC cases achieved pCR. Similarly, 189 (84%) of 225 cases indicated as non-cCR by interim MRI were non-pCR, whereas 94 (95%) of 99 non-cCR luminal-type cases were non-pCR. Conclusion Interim MRI could predict treatment response at an early stage in breast cancer patients receiving NAC.