Journal des rapports de cas cliniques

Pathological Complete Response with CDK 4/6 Inhibitors in HR+/HER2- Locally Breast Cancer: Case of a Benign Bone Lesion Misidentified as Metastatic

Abstract

Bekkouche Soukaina, Najem Salma, Harrak Soukaina, Abdi Chaimae, M’rabti Hind, Boutayeb Saber, El Guisssassi Ibrahim and Errihani Hassan

Locally advanced breast cancer presents significant challenges to the multidisciplinary team, particularly in cases involving hormone receptor (HR)-positive, HER2-negative tumors, which typically show lower rates of pathological complete response to chemotherapy. Cyclin-Dependent Kinase (CDK) 4/6 inhibitors are the cornerstone of treatment in metastatic Hormone Receptor (HR)-positive, HER2-negative breast cancer and have more recently been considered in the adjuvant setting. However, their effectiveness in the neoadjuvant setting remains uncertain.

We report the case of a 55-year-old postmenopausal woman initially diagnosed with metastatic HR+/HER2- breast cancer due to a unique L5 bone lesion. Systemic treatment was initiated with an Aromatase Inhibitor (AI) and a CDK4/6 inhibitor. After six months of treatment, imaging reevaluation confirmed that the L5 lesion, which had remained unchanged, was benign, allowing for curative surgery. Final pathology revealed a complete histological response with no residual tumor, highlighting the potential of CDK4/6 inhibitors in managing locally advanced HR+/HER2- breast cancer.