本研究的目的是调查弥散加权成像 (DWI) 与动态对比增强 (DCE)-MRI 的附加值，以确定 HER2 阳性乳腺癌患者的病理学完全缓解 (pCR) 和放射学完全缓解(rCR)。这是一项单中心观察性研究，对象为 102 名 I-III 期 HER2 阳性乳腺癌患者，并在 DCE-MRI 上记录了真实世界的 rCR。患者于 2015 年至 2019 年间接受治疗。均使用 1.5 T/3.0 T 单次扩散加权回波平面序列。新辅助全身治疗 (NST) 后弥散加权图像由两名读者进行审查，以进行视觉评估和 ADC 平均值。不一致的情况在协商一致会议上得到解决。乳房的 pCR (ypT0/is) 用于计算阴性预测值 (NPV)。乳腺 pCR 百分比通过 Fisher 精确检验进行测试。使用 Mann-Whitney U 检验比较有和没有 pCR 的患者的 ADCmean 和 ΔADCmean(%)。在激素受体 (HR)-/HER2 中，添加 DCE 的 DWI 的 NPV 为 86%，而单独使用 DCE 的 NPV 为 87% - 阳性和 67%，而 HR 阳性/HER2 阳性乳腺癌的这一比例为 64%。 39 例非 rCR DWI 病例中有 27 例为假阳性。在 HR 阴性/HER2 阳性乳腺癌中，DCE MRI 的 NPV 因 MRI 场强而异（1.5 T：50% 与 3 T：81% [p = 0.02]）。在有和没有 pCR 的患者之间，基线时的 ADC 平均值、NST 后和 ΔADC 平均值相似。DWI 对单独用于确定早期 HER2 阳性乳腺癌的 pCR 的 DCE 的 NPV 没有临床相关影响。考虑到 MRI 场强，DWI 在 HR 阳性/HER2 阳性乳腺癌中的附加值应进一步研究。早期 HER2 阳性乳腺癌新辅助全身治疗后 DWI 上的残留信号，且无残留病理强化。 DCE-MRI 乳房（尚）不应被考虑用于评估完全放射学缓解。放射学完全缓解与 HER2 乳腺癌的病理学完全缓解 (pCR) 相关，但有必要进一步改进。当 DCE 添加 DWI 时，没有观察到阴性预测值的相关增加。 DCE-MRI 上没有病理增强的 DW 图像上的残留信号并不表明 pCR 的可能性较低。© 2024。作者。

The aim of this study is to investigate the added value of diffusion-weighted imaging (DWI) to dynamic-contrast enhanced (DCE)-MRI to identify a pathological complete response (pCR) in patients with HER2-positive breast cancer and radiological complete response (rCR).This is a single-center observational study of 102 patients with stage I-III HER2-positive breast cancer and real-world documented rCR on DCE-MRI. Patients were treated between 2015 and 2019. Both 1.5 T/3.0 T single-shot diffusion-weighted echo-planar sequence were used. Post neoadjuvant systemic treatment (NST) diffusion-weighted images were reviewed by two readers for visual evaluation and ADCmean. Discordant cases were resolved in a consensus meeting. pCR of the breast (ypT0/is) was used to calculate the negative predictive value (NPV). Breast pCR-percentages were tested with Fisher's exact test. ADCmean and ∆ADCmean(%) for patients with and without pCR were compared using a Mann-Whitney U-test.The NPV for DWI added to DCE is 86% compared to 87% for DCE alone in hormone receptor (HR)-/HER2-positive and 67% compared to 64% in HR-positive/HER2-positive breast cancer. Twenty-seven of 39 non-rCR DWI cases were false positives. In HR-negative/HER2-positive breast cancer the NPV for DCE MRI differs between MRI field strength (1.5 T: 50% vs. 3 T: 81% [p = 0.02]). ADCmean at baseline, post-NST, and ∆ADCmean were similar between patients with and without pCR.DWI has no clinically relevant effect on the NPV of DCE alone to identify a pCR in early HER2-positive breast cancer. The added value of DWI in HR-positive/HER2-positive breast cancer should be further investigated taken MRI field strength into account.The residual signal on DWI after neoadjuvant systemic therapy in cases with early HER2-positive breast cancer and no residual pathologic enhancement on DCE-MRI breast should not (yet) be considered in assessing a complete radiologic response.Radiologic complete response is associated with a pathologic complete response (pCR) in HER2+ breast cancer but further improvement is warranted. No relevant increase in negative predictive value was observed when DWI was added to DCE. Residual signal on DW-images without pathologic enhancement on DCE-MRI, does not indicate a lower chance of pCR.© 2024. The Author(s).