PET imaging reliable for evaluating new cancer therapies: Study

USA: According to a recent study in the Journal of Nuclear Medicine, FAPi PET imaging of cancer patients with a gallium-68 (Ga-68) tracer may be a reliable way for evaluating new therapies. 

According to results from the interim analysis of a prospective exploratory imaging trial, 68Ga-FAPi-46 PET biodistribution across multiple cancers strongly correlated with fibroblast activation protein (FAP) tissue expression. The findings support further investigation of FAPi PET as a pan-cancer imaging biomarker for FAP expression and stratification tool for FAP-targeted therapies.

FAP-expressing cancer-associated fibroblasts are known to promote metastasis and immunosuppression and confer treatment resistance. Radiolabeled molecules targeting FAP are being used as pan-cancer theranostic agents because FAP is overexpressed in many cancers. 

Christine E. Mona, University of California Los Angeles, United States, and colleagues aimed to establish the spectrum of FAP expression across various cancers by immunohistochemistry and to explore whether gallium-68 FAPi-46 (68Ga-FAPi-46) PET biodistribution faithfully reflects FAP expression from resected cancer and non-cancer specimens.

For this purpose, the researchers conducted a FAP expression screening by using immunohistochemistry on a pan-cancer human tissue microarray (TMA) (141 patients, 14 different types of cancer) and an interim analysis of a prospective exploratory imaging trial in cancer patients.

Volunteer patients 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. 

"These findings support further exploration of FAPi PET as a pan-cancer imaging biomarker for FAP expression and stratification tool for FAP- targeted therapies," the authors concluded. 

Reference:

Correlation of 68Ga-FAPi-46 PET biodistribution with FAP expression by immunohistochemistry in patients with solid cancers: a prospective translational exploratory study. 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. Journal of Nuclear Medicine Nov 2021, jnumed.121.262426; DOI: 10.2967/jnumed.121.262426