# Metabolic response prediction using 68Ga-FAPI PET/CT in Non-Hodgkin lymphoma treated with chemotherapy: a pilot study

## TL;DR

This study explores how 68Ga-FAPI PET/CT scans can predict how well Non-Hodgkin lymphoma patients will respond to chemotherapy.

## Contribution

This is the first pilot study to evaluate the predictive value of 68Ga-FAPI PET/CT for metabolic response in NHL patients undergoing CHOP-like chemotherapy.

## Key findings

- 68Ga-FAPI PET/CT parameters like SUVmax, TBRblood, and TBRmuscle were significantly higher in responders than non-responders.
- SUVmax showed strong predictive accuracy with a high area under the curve (AUC) value.
- Low radiotracer uptake in 68Ga-FAPI PET/CT was linked to poor metabolic response to chemotherapy.

## Abstract

The aim of this study was to investigate the prediction value of metabolic response using gallium 68 (68Ga) labeled fibroblast-activation protein inhibitor (68Ga-FAPI) positron emission tomography-computed tomography (PET/CT) in Non-Hodgkin lymphoma (NHL) patients receiving (cyclophosphamide-doxorubicin HCl-vincristine[Oncovin]- prednisone) CHOP-like chemotherapy.

This single-center prospective study was conducted in our hospital and enrolled participants who was initially diagnosed with NHL and received CHOP-like chemotherapy. 68Ga-FAPI PET/CT was performed before chemotherapy. Metabolic response was assessed by fluorine 18 (18F) labeled fluorodeoxyglucose (18F-FDG) PET/CT. Quantitative analysis included measurement of the maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), peak standardized uptake value (SUVpeak), metabolic tumor volume (MTV) and total lesion FAP (TLF). The SUVmax value of the lesion is divided by SUVmean of normal tissue to calculate the target-to-background ratio (TBRblood and TBRmuscle). Depending on the response, participants were categorized as responders and non-responders. Mann-Whitney U-test was used to compare the 68Ga-FAPI PET/CT parameters of responders with that of non-responders. Logistic regression analyses were performed to determine the relationship between clinical characteristics, 68Ga-FAPI PET/CT parameters, and efficacy of chemotherapy. Receiver operating characteristic curve analysis was used to identify the accuracy of 68Ga-FAPI PET/CT parameters for response prediction.

From October 2022 to May 2023, 18 participants (10 men and 8 women; median age: 56 years [interquartile range: 47–67 years]) with pathologically confirmed diagnosis of non-Hodgkin’s lymphoma were recruited in our hospital and enrolled in this study. The mean values of SUVmax, TBRblood, and TBRmuscle were significantly higher in responders than those in non-responders (8.41\documentclass[12pt]{minimal}
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\begin{document}$$\:\pm\:$$\end{document}1.73 P = 0.025; respectively). The area under the curve (AUC) of SUVmax, TBRblood, and TBRmuscle were statistically significant (0.875, P = 0.025; 0.857, P=0.034; 0.875, P = 0.026, respectively). SUVmax (OR=0.592, P = 0.041) is a significant factor in the prognosis of these participants.

Low radiotracer uptake on 68Ga-FAPI PET/CT indicated poor metabolic response of NHL patients received CHOP-like therapy. SUVmax could be used to screen sensitive patients.