Sustained remission after cord blood transplantation for breast cancer with lung metastases and myelodysplastic syndrome.

Allogenic hematopoietic stem cell transplantation (allo-HSCT) is not a standard therapy for solid cancer because of its high toxicity and insufficient evidence levels. However, the potential graft-versus-solid-tumor (GVT) effect of this therapy has been discussed. Many case reports have also described treatment effects of allo-HSCT in patients with hematologic malignancies and active solid tumors. A 38-year-old woman treated with fulvestrant and abemaciclib for recurrent breast cancer with multiple lung metastases was diagnosed with myelodysplastic syndrome (MDS) with increased blasts 2. She was classified as adverse risk by the 2017 European LeukemiaNet risk stratification and as very high risk by the Molecular International Prognostic Scoring System. Breast cancer treatment was interrupted and venetoclax and azacitidine therapy was started. Complete hematologic response was achieved after three cycles. However, multiple lung metastases from the breast cancer remained. The patient then underwent umbilical cord blood transplantation. She has maintained complete remission of MDS as of 1 year post-transplantation, without serious complications. Lung metastatic activity on FDG-PET/CT scan also completely disappeared by half a year post-transplantation, and this response has continued as of 1 year post-transplantation. This favorable treatment course suggests the existence of a GVT effect.