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

Background: 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.

Method: 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.

Results: 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[Formula: see text]3.90 vs. 3.98[Formula: see text]2.81 P=0.025; 7.93[Formula: see text]3.31 vs. 3.69[Formula: see text]2.36 P=0.035; 7.04[Formula: see text]3.22 vs. 3.09[Formula: see text]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.

Conclusion: 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.