Durable Response to Ribociclib?Fulvestrant in Breast Cancer With Pancreatic Metastasis and Neuroendocrine Features: A Case Report

Abstract

Author(s): Nejjari Sara*, Keita Diango, Alem Mehdi, Oufrid Abir, El Hilali Hafssa, Chbihi Chaymae, El Hakym Samia, Aabboub Basma, Amaadour Lamiae, Oualla Karima, Benbrahim Zineb, Arifi Samia, Mayeur Didier and Mellas Nawfel

Invasive breast carcinoma with neuroendocrine differentiation (BC-NED) is a rare and distinct subtype. The combination of a rare metastatic site like the pancreas and a rare tumor subtype, as seen in our patient, presents a unique clinical scenario. We report the case of a 53-year-old female who was initially treated in 2011 for an HR+/HER2+ invasive ductal carcinoma of the right breast. After receiving adjuvant therapy, the patient developed a lesion in the pancreatic head in February 2020. Histopathological analysis confirmed the presence of a carcinoma consistent with a breast origin, but with the emergence of a neuroendocrine component. Systemic treatment with ribociclib plus fulvestrant was initiated. The patient achieved a complete clinical and radiological metabolic response with this regimen, which has been maintained to date with good treatment tolerance. The prognosis for patients with pancreatic metastases is generally poor, which makes our patient's exceptional response particularly intriguing. The de-novo emergence of the neuroendocrine component during metastasis is a fascinating aspect of this case, suggesting a potential clonal evolution. While most trials of CDK4/6 inhibitors excluded patients with neuroendocrine tumors, this case demonstrates the potential for their use in this setting. This case report illustrates that breast cancer with a neuroendocrine component, even in the context of visceral metastasis, can have a durable and favorable response to targeted endocrine therapy in combination with a CDK4/6 inhibitor. This finding highlights the importance of a thorough pathological and molecular evaluation to guide treatment decisions.

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