Metastatic HER2-positive breast cancer complicated by severe low magnesium

What happened, in summary

A 58-year-old woman had been treated for localized HER2-positive breast cancer in 2019 with surgery. The cancer later returned and eventually spread to the bone, lungs, liver, and brain, making it Stage IV.

From 2023 onward, she received several chemotherapy regimens as treatment changed with disease progression. Carboplatin was given during 2023 and again from June through December 2024. She also received radiation to painful metastatic areas in the lower spine and right hip.

Over time, she developed severe low magnesium levels related to kidney magnesium loss after carboplatin. The problem became especially severe months after the last carboplatin treatment. She was admitted with widespread pain, fatigue, and electrolyte abnormalities and needed magnesium and calcium replacement.

As her advanced cancer and complications progressed, her priority became relief from pain. Oral magnesium was difficult because of painful mouth ulcers. During her final hospitalization, her pain treatment was adjusted so that she could remain comfortable. She died with her care focused on comfort, a goal valued by both her and her family.