Heterogeneous Response After [ 177 Lu]Lu-FAPI-2286 Combination Therapy in Metastatic Breast Cancer.

A 37-year-old woman with metastatic invasive ductal carcinoma, resistant to anti-HER 2 therapy, underwent [ 177 Lu]Lu-FAPI-2286 radionuclide therapy combined with antibody-drug conjugate chemotherapy. Baseline [ 68 Ga]Ga-FAPI-2286 PET/CT confirmed extensive fibroblast activation protein expression in metastatic sites. After 5 cycles, follow-up imaging showed a significant reduction in FAPI uptake in skin lesions, resolution of bone lesions, and decreased pleural thickening. Clinically, the patient reported pain relief and resolution of lymphedema. However, new metastases emerged in cervical, mediastinal, and abdominopelvic lymph nodes, indicating a heterogeneous response, and biopsy of these newly emerged lymph nodes confirmed disease recurrence.