177 Lu-FAPI-2286 Therapy in Metastatic Breast Cancer : A Case Study Highlighting the Potential Risk of Tumor Dedifferentiation and Hormonal Marker Elevation.

Raeisi, Nasrin; Saber Tanha, Amin; Aryana, Kamran; Homaee Shandiz, Fatemeh; Barashki, Somaye · Clin Nucl Med · 2026

case_report · Level V

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Abstract

This case report presents a 42-year-old woman with metastatic breast cancer refractory to multiple conventional treatments, including surgery, chemotherapy, radiotherapy, hormonal therapy, and bilateral oophorectomy. As a salvage, she received 177 Lu-FAPI-2286 radioligand therapy. After the first cycle, an unexpected serum β-hCG elevation was observed-unusual given her history of total hysterectomy and bilateral salpingo-oophorectomy. Three hypotheses were proposed: assay interference (heterophile antibodies), emergence of second neoplasm secreting β-hCG, and tumor dedifferentiation with ectopic β-hCG expression. Unfortunately, rapid clinical progression precluded further evaluation. This case underscores the importance of awareness regarding tumor dedifferentiation and biomarker changes during novel theranostic treatments with 177 Lu-FAPI, emphasizing the need for vigilant multidisciplinary monitoring.

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