What happened, in summary

A 54-year-old woman was diagnosed with left breast invasive carcinoma in March 2018. The tumor was estrogen-receptor positive, progesterone-receptor negative, and HER2-positive. She underwent modified radical mastectomy with axillary lymph node dissection. A supraclavicular lymph-node biopsy soon afterward also showed metastatic breast carcinoma.

She received 8 cycles of docetaxel with trastuzumab and pertuzumab, then continued trastuzumab and pertuzumab with letrozole. Radiation therapy was completed in March 2019. In December 2020, imaging showed new metastatic disease involving axillary and intra-abdominal lymph nodes and bone. She started trastuzumab emtansine, or T-DM1, with zoledronic acid, and scans 3 months later showed marked regression.

After about 18 months on T-DM1, she developed leg redness, joint pain, fatigue, and autoimmune blood-test abnormalities. In 2023 she was diagnosed with drug-induced lupus. Her symptoms improved after hydroxychloroquine was started and T-DM1 was stopped. The cancer had also progressed on T-DM1. More than 5 years after her March 2018 diagnosis, she was living with metastatic breast cancer, but the disease had progressed on T-DM1 and treatment had been stopped.