Stage 4 HR-positive breast cancer: stable disease on ribociclib

What happened, in summary

A 46-year-old woman with Raynaud’s syndrome and hypothyroidism was diagnosed in 2002 with HR-positive, HER2-negative, low-grade invasive breast cancer of the right breast. The primary tumor was pT1c pN1a M0, with ER 95% and PR 95%. She underwent right radical mastectomy, followed by 6 cycles of adjuvant docetaxel, cyclophosphamide, and doxorubicin. She also received irradiation of the affected breast region and supra- and infraclavicular nodes, then took tamoxifen for 7 years. She remained relapse-free until August 2021, when hip pain led to bone scintigraphy and CT showing a suspicious left iliac lesion and nonspecific lung nodules. Biopsy of the iliac lesion confirmed metastatic breast cancer, with ER 100%, PR 100%, and HER2-negative status. In September 2021, she started ribociclib 600 mg/day on a 3-weeks-on, 1-week-off schedule plus continuous letrozole 2.5 mg/day. PET/CT in November 2021 showed no other metabolic disease beyond the known left iliac lesion. SBRT to that bone metastasis was delivered in January 2022, with ribociclib held for 3 weeks to avoid overlap with radiation. She developed palinopsia, a visual symptom involving lingering motion images, temporally linked to ribociclib. Neurologic, neuro-ophthalmologic, retinal, visual-field, laboratory, and brain MRI workup found no other cause. In April 2022, ribociclib was reduced to 400 mg/day. No other active PET-avid disease was identified. As of October 2024, she had very mild, non-daily palinopsia and no disease progression on ribociclib plus letrozole. Her outcome is ongoing control of metastatic HR-positive breast cancer on systemic therapy, rather than cancer-free disease.