Multiple myeloma is a hematological cancer characterized by relapse after treatment and poor prognosis. Ixazomib, a second-generation protease inhibitor, is one of the most recently available treatments for relapsed or refractory multiple myeloma, while it has also shown good potential as antitumoral agent in preclinical solid tumor models such as breast cancer cell lines. Here we report the case of a 68-year-old female with multiple myeloma and an incidental cT1b (9 mm) hormone receptor positive breast cancer lesion that showed a complete pathological response to a three-month combination therapy with Ixazomib, bendamustine and dexamethasone and no signs of disease relapse during the later follow-up. This is the first case report describing such clinical outcome in breast cancer following Ixazomib, bendamustine and dexamethasone combination therapy. To investigate the potential antitumoral activity of Ixazomib in breast cancer, we performed in vitro experiments using two hormone receptor positive breast cancer cell lines. We assessed the synergism between Ixazomib and bendamustine and the antiproliferative effect of Ixazomib. We found no synergistic interaction between the two drugs, while Ixazomib alone showed an antiproliferative effect against tumoral cells, suggesting that this drug has been responsible for tumor regression in our case.

中文翻译：

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伊沙佐米治疗多发性骨髓瘤患者激素受体阳性浸润性乳腺癌的完全病理反应。

多发性骨髓瘤是一种以治疗后复发和预后不良为特征的血液系统恶性肿瘤。Ixazomib 是一种第二代蛋白酶抑制剂，是最近可用于治疗复发或难治性多发性骨髓瘤的药物之一，同时它在临床前实体瘤模型（如乳腺癌细胞系）中也显示出作为抗肿瘤药物的良好潜力。在这里，我们报告了一名患有多发性骨髓瘤和偶发的 cT1b (9 mm) 激素受体阳性乳腺癌病变的 68 岁女性病例，该病例显示对伊沙佐米、苯达莫司汀和地塞米松的三个月联合治疗有完全的病理反应，并且后期随访无疾病复发迹象。这是第一份描述伊沙佐米治疗后乳腺癌临床结果的病例报告，苯达莫司汀和地塞米松联合治疗。为了研究伊沙佐米在乳腺癌中的潜在抗肿瘤活性，我们使用两种激素受体阳性乳腺癌细胞系进行了体外实验。我们评估了伊沙佐米和苯达莫司汀之间的协同作用以及伊沙佐米的抗增殖作用。我们发现这两种药物之间没有协同作用，而 Ixazomib 单独显示出对肿瘤细胞的抗增殖作用，这表明在我们的案例中这种药物是导致肿瘤消退的原因。