Breast Cancer Recurring Years Later With Leptomeningeal Spread and a Brief Response to Trastuzumab Deruxtecan

What happened, in summary

A 65-year-old woman had originally been diagnosed with Stage III invasive lobular carcinoma of the left breast in April 2006. She underwent modified radical mastectomy and axillary lymph node dissection, followed by chemotherapy, radiation, and several years of endocrine therapy.

She remained under surveillance until 2018, when abdominal pain led to discovery of a large pelvic mass. Surgery confirmed metastatic lobular breast cancer involving the peritoneum. She began palbociclib with endocrine therapy and achieved a complete radiologic response. In 2022, however, the cancer progressed in the retroperitoneum and peritoneum and spread to the spine. She received capecitabine and later weekly paclitaxel.

By December 2023, she developed headaches, weakness, and leptomeningeal disease with hydrocephalus. Trastuzumab deruxtecan was started in January 2024. Her headaches resolved and her weakness and quality of life improved quickly, but after three cycles she developed drug-related interstitial lung disease and treatment was stopped. Neurologic symptoms then returned, and she became too unwell for further therapy. She entered hospice care and died on May 10, 2024—about 18 years after her initial breast-cancer diagnosis and about 6 years after metastatic recurrence.