The Role of 68Ga-FAPI PET/CT in Breast Cancer Response Assessment and Follow-Up

Abstract

Purpose 68Ga–fibroblast activation protein inhibitor (FAPI), a new PET/CT radiotracer targeting cancer-associated fibroblasts in tumor microenvironment, can detect many types of cancer. We aimed to assess whether it can also be used for response assessment and follow-up. Methods We followed up patients with FAPI-avid invasive lobular breast cancer (ILC) before and after treatment changes and correlated qualitative maximal intensity projection images and quantitative tumor volume with CT results and blood tumor biomarkers. Results Six consenting ILC breast cancer patients (53 ± 8 years old) underwent a total of 24 scans (baseline for each patient and 2–4 follow-up scans). We found a strong correlation between 68Ga-FAPI tumor volume and blood biomarkers (r = 0.7, P < 0.01), but weak correlation between CT and 68Ga-FAPI maximal intensity projection–based qualitative response assessment. Conclusions We found a strong correlation between ILC progression and regression (as assessed by blood biomarkers) and 68Ga-FAPI tumor volume. 68Ga-FAPI PET/CT could possibly be used for disease response assessment and follow-up.