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Publications

Journal Article Ahead of print

PubMed: 42609054 DOI: 10.4274/mirt.galenos.2026.21957

The role of 68Ga-FAPi PET/CT in Staging and Restaging of Breast Cancer Subtypes with Limited 18F-FDG Uptake.

Mol Imaging Radionucl Ther

Authors: Gamze Beydağı, Nalan Alan Selçuk, Kaan Akçay, Ayşegül Görmez, Neşet Köksal, Serkan Çelik, Bala Başak Öven, Levent Kabasakal

Affiliations

  • Yeditepe University Faculty of Medicine, Department of Nuclear Medicine, İstanbul, Türkiye.
  • Yeditepe University Faculty of Medicine, Department of Radiology, İstanbul, Türkiye.
  • Yeditepe University Faculty of Medicine, Department of Surgery, İstanbul, Türkiye.
  • Yeditepe University, Faculty of Medicine, Department of Medical Oncology, İstanbul, Türkiye.
  • İstanbul University-Cerrahpaşa, Cerrahpaşa Faculty of Medicine, Department of Nuclear Medicine, İstanbul, Türkiye.

Abstract

OBJECTIVES

Breast cancer is highly heterogeneous, and certain histopathologic subtypes-particularly invasive lobular carcinoma-exhibit low glucose metabolism that limits 18F-fluorodeoxyglucose positron emission tomography/computed tomography ( 18F-FDG PET/CT) performance. Fibroblast activation protein inhibitor (FAPi) imaging with Gallium-68 ( 68Ga)-FAPi PET/CT has emerged as a promising alternative for such tumors. The aim of this study was to evaluate the efficacy of 68Ga-FAPi PET/CT in staging, restaging, and recurrence detection of breast cancer, with emphasis on subtypes for which 18F-FDG PET/CT has low sensitivity.

METHODS

Twenty-nine women with pathologically confirmed breast cancer (mean age 57.7±11.6 years) were prospectively enrolled. Histopathology (available in 24 patients) showed lobular carcinoma in 16, ductal carcinoma in 6, signet ring cell carcinoma in 1, and mucinous carcinoma in 1. All underwent both 68Ga-FAPi and 18F-FDG PET/CT within one week for staging or restaging. Maximum standardized uptake values (SUV max) of primary tumors and metastases were recorded for both tracers and compared using paired t-tests.

RESULTS

In 7/29 patients (24.1%), neither 18F-FDG PET/CT nor 68Ga-FAPi PET/CT detected pathological findings. Disease stage increased in 13/29 (44.8%) after 68Ga-FAPi PET/CT, including 10 patients with no pathologic findings on 18F-FDG PET/CT; nine were upstaged to stage 4 and one to stage 3. Additionally, one patient progressed from stage 1 to 2, one from 2 to 3, and another from 3 to 4. Among patients with lobular carcinoma, 8/16 (50%) were upstaged with 68Ga-FAPi PET/CT. Detection of nodal and distant metastases in lobular carcinoma was higher with 68Ga-FAPi than 18F-FDG. 68Ga-FAPi PET/CT also demonstrated higher SUV max in primary lesions and metastases (p<0.05).

CONCLUSION

68Ga-FAPi PET/CT provides a significant advantage for staging and restaging breast cancer-especially lobular carcinoma and other low 18F-FDG-avid subtypes-supporting its potential role in clinical decision-making and treatment planning.

MeSH

Breast Neoplasms, Tomography, Neoplasms, Positron Emission Tomography Computed Tomography, Fluorodeoxyglucose F18, Neoplasm Metastasis, Breast, Carcinoma, Lobular