PET Imaging May Reliably Evaluate New Cancer Treatments

Targeting fibroblast activation protein (FAP) with gallium-68 FAPi-46 (68Ga-FAPi-46) PET, an experimental radiotracer, may prove to be a reliable way to evaluate new cancer treatments, according to a study published November 5, 2021, in the Journal of Nuclear Medicine.

“In this interim analysis of a prospective exploratory imaging trial, 68Ga-FAPi-46 PET biodistribution across multiple cancers strongly correlated with FAP tissue expression. These findings support further exploration of FAPi PET as a pan-cancer imaging biomarker for FAP expression and stratification tool for FAP- targeted therapies,” wrote the team of researchers at the University of California, Los Angeles (UCLA).

“Volunteer patients [n=141, with 14 different types of cancer] underwent one whole body 68Ga-FAPi-46 PET/CT scan and subsequently, surgical resection of their primary tumor and/or metastasis. 68Ga-FAPi-46 PET maximum standardized uptake value (SUVmax and SUVmean) was correlated with FAP immunohistochemistry score in cancer and non-cancer tissues for each patient. … FAP was expressed across all 14 cancers types on TMA with variable intensity and frequency, ranging from 25 to 100% (mean 76.6±25.3%),” noted the team.

Evaluation of the resected cancers showed that “FAP immunohistochemistry scores strongly correlated with 68Ga-FAPi 46 SUVmax and SUVmean: r=0.781 (95%CI 0.376-0.936; p<0.001) and r=0.783 (95%CI 0.379-0.936; p<0.001), respectively," found the team.

Lead author Mona and the team concluded, “In this interim analysis of a prospective exploratory imaging trial, 68Ga-FAPi-46.PET biodistribution correlated strongly with FAP expression in cancer and non-cancer tissues across multiple cancer types. These data support the use of 68Ga-FAPi-46 PET as a pan-cancer predictive biomarker and stratification tool for FAP-targeted therapeutic approaches and lay the foundation for future evaluation of FAPi ligand labeled with therapeutic isotopes in clinical trials.”


Christine E. Mona, Matthias R. Benz, Firas Hikmat, Tristan R. Grogan, Katharina Lückerath, Aria Razmaria, Rana Riahi, Roger Slavik, Mark D. Girgis, Giuseppe Carlucci, Kimberly A. Kelly, Samuel W French, Johannes Czernin, David W. Dawson, Jeremie Calais. Correlation of 68Ga-FAPi-46 PET biodistribution with FAP expression by immunohistochemistry in patients with solid cancers: a prospective translational exploratory study. Journal of Nuclear Medicine Nov 2021, jnumed.121.262426; DOI: 10.2967/jnumed.121.262426 Published online November 5, 2021, at Accessed November 15, 2021.

Morton, Will. PET imaging lays foundation for new cancer therapies. Published online November 8, 2021, at Accessed November 15, 2021.

Graphical Abstract
Unaltered image used under a Creative Commons CC-BY license. Image from the study cited first under “Sources” in the text.