Anti-trophoblast Cell-Surface Antigen 2 (TROP2)-Based Therapy for Concurrent Breast and Thyroid Malignancies

The simultaneous presence of thyroid carcinoma with other non-thyroid malignancies poses unique treatment dilemmas.Optimal treatment strategies for patients with simultaneous papillary thyroid carcinoma and breast cancer have not been clearly identified.There is increasing attention focused on targeting molecular markers common to both tumors, such as trophoblast cell surface antigen 2 (Trop-2).Herein, we report an 86-year-old female with hormone receptor-positive, HER2-low metastatic breast cancer and an RAI-refractory, BRAF V600E-mutated, metastatic papillary thyroid carcinoma with Trop-2 expression.Following four cycles of sacituzumab govitecan for the breast cancer, she was re-staged.Radiographic studies revealed a partial response to the regimen for the pulmonary metastases along with improvement in thyroglobulin levels and marked reduction of breast tumor markers.This case highlights the possibility of cross-tumor efficacy of Trop-2 targeted agents, thus providing the rationale that sacituzumab govitecan should be explored in RAI-refractory differentiated thyroid cancer.