CDK4/6 and aromatase inhibitors as first-line treatment in metastatic high-grade neuroendocrine carcinoma of the breast: A case report

Abstract

Key clinical message: There is no consensus regarding the therapeutic approach of breast neuroendocrine carcinomas (NECs). As most NECs are hormone receptor positive and HER-2 negative, we suggest that endocrine-based strategies may play a leading role. Here, we report a new treatment strategy by incorporating CDK4/6 inhibitors in the therapeutic armamentarium.

Abstract: Primary neuroendocrine neoplasms of the breast constitute a rare entity. They are characterized by predominant neuroendocrine differentiation and are further divided into well-differentiated neuroendocrine tumors and poorly differentiated (high-grade) neuroendocrine carcinomas (NECs). Regarding their therapeutic approach, there are no standardized guidelines. Herein, we present the first case ever reported, concerning a female patient with de novo metastatic breast NEC who received hormonal therapy, a combination of a CDK4/6 inhibitor palbociclib with letrozole and triptorelin, as first-line treatment with significant clinical and radiological response. As most NECs are estrogen receptor and/or progesterone receptor positive and HER-2 negative, we suggest that hormonal therapy may play a leading role even in the first-line setting. The present report provides a new treatment strategy by incorporating CDK4/6 inhibitors in the therapeutic armamentarium of breast NECs.

Keywords: CDK4/6 inhibitors; breast neuroendocrine carcinoma; hormonal therapy; treatment strategy.

FIGURE 1

On immunohistochemistry, tumor cells show diffuse positive staining for estrogen receptor (A), chromogranin (B), and synaptophysin (C) (×200).

FIGURE 2

Contrast‐enhanced computed tomography scans of the thorax. Left breast mass before treatment initiation (A) and after 3 months of therapy (B). Left axillary lymphadenopathy before treatment initiation (C) and 3 months after (D). Red arrows indicate the tumor area.

FIGURE 3

Contrast‐enhanced computed tomography scans of the abdomen showing the metastatic liver lesions before treatment initiation (A, C) and 3 months after (B, D). Red circles highlight the tumor areas.