Metastatic triple-negative breast cancer with orbital and bone metastases responding to nab-paclitaxel plus everolimus

What happened, in summary

This 72-year-old woman had been treated 3 years earlier for cT2N0 breast cancer that was ER-low positive at 5%, PR-negative, and HER2-negative. Initial treatment included modified radical mastectomy, 6 cycles of docetaxel/cyclophosphamide chemotherapy, and tamoxifen 20 mg daily. She later developed 3 months of right and left orbital pain, double vision, and periorbital swelling. Examination showed right conjunctival hyperemia, increased exudate, and reduced right-eye visual acuity. Orbital MRI showed multiple extraocular muscle inflammation, compressive displacement of the optic nerve, and right periorbital edema. Because of her breast cancer history, clinicians performed full staging. Bone scintigraphy and whole-body CT revealed extensive bone metastases. A right orbital mass biopsy confirmed metastatic invasive ductal carcinoma of the breast. The metastatic tumor was ER-negative, PR-negative, and HER2-negative, making it triple-negative at recurrence. Next-generation sequencing found an AKT1 exon 4 mutation, indicating activation of the PI3K/AKT/mTOR pathway. Her subtype was categorized as Luminal Androgen Receptor / PI3K-AKT-mut within the Fudan TNBC classification. Treatment was selected based on this profile. She started nab-paclitaxel 100 mg/m2 on days 1, 8, and 15 combined with everolimus 10 mg daily. Zoledronic acid 4 mg monthly was added to reduce skeletal-related event risk from bone metastases. At 6-month follow-up, she had stable systemic disease, significant improvement in ocular symptoms, stable orbital metastases on MRI, and a RECIST partial response/progression-free interval. Ongoing surveillance included orbital MRI and circulating tumor DNA monitoring. The receptor change from ER-low primary disease to triple-negative metastatic disease also guided the shift away from endocrine therapy toward chemotherapy plus pathway-directed treatment.