18F-Fluorodeoxyglucose Uptake in PDGFRA-Mutant Gastrointestinal Stromal Tumors
Authors: Nigro Maria Concetta , Marchetti Andrea , Fumagalli Elena Rosa , De Luca Ida , Bertuzzi Alexia Francesca , Grimaudo Maria Susanna , Grignani Giovanni , D’Ambrosio Lorenzo , Merlini Alessandra , Badalamenti Giuseppe , Incorvaia Lorena , Dimino Alessandra , Gasperoni Silvia , Vincenzi Bruno , Fanti Stefano , Di Federico Alessandro , Campana Davide , Pantaleo Maria Abbondanza , Nannini Margherita ,   Tumori Rari Bologna, Astolfi Annalisa , Costa Alice , Ianni Manuela , Del Gaudio Massimo , de Biase Dario , Pirini Maria Giulia 
Published: January 2025

ImportanceThe D842V platelet-derived growth factor receptor α (PDGFRA) mutation identifies a molecular subgroup of gastrointestinal stromal tumors (GISTs), primarily resistant to standard tyrosine kinase inhibitors and with an overall more indolent behavior. Although functional imaging with 18F-fluorodeoxyglucose–labeled positron emission tomography ([18F]FDG-PET) plays a proven role in GISTs, especially in early assessment of tumor response, less is known about [18F]FDG uptake according to the GIST molecular subtypes.ObjectiveTo evaluate the degree of [18F]FDG uptake in PDGFRA-mutant GISTs and better define the role of functional imaging in this rare and peculiar subset of GISTs.Design, Setting, and ParticipantsThis multi-institutional retrospective cohort study involving 7 GIST reference centers in Italy included patients with PDGFRA-mutant GIST who underwent [18F]FDG-PET from January 1, 2000, to December 31, 2023. Data on the maximum standardized uptake value (SUVmax) of primary tumor or metastatic disease were collected.ExposurePDGFRA-mutant GIST and [18F]FDG-PET.Main Outcome and MeasureThe primary outcome was the degree of [18F]FDG uptake of PDGFRA-mutant GISTs, with a focus on the D842V-mutant subgroup. Secondary objectives were to assess the association between the degree of [18F]FDG uptake and main clinicopathologic features.ResultsA total of 71 patients with PDGFRA-mutant GISTs were included in the analysis: 37 (52.1%) in the D842V subgroup (group A) and 34 (47.9%) in the non-D842V subgroup (group B). Additionally, 70 patients with KIT exon 11–mutant GIST served as a control group (group C). For all 141 participants, the median age at diagnosis was 59 (range, 26-89) years, and 81 patients (57.4%) were male. Overall, the median SUVmax was 4.4 (IQR, 0-10.1), while the median SUVmax for group A was 0 (IQR, 0-3.2); for group B, 3.6 (IQR, 0-5.1); and for group C, 10.1 (IQR, 5.1-13.9). The median SUVmax of PDGFRA-mutant GISTs was significantly lower than the median value of KIT exon 11–mutant GISTs (0 [IQR, 0-4.3] vs 10.1 [IQR, 5.1-14.0]; P &amp;lt; .001). Median [18F]FDG uptake was significantly lower in the D842V subgroup compared with the non-D842V subgroup (0 [IQR, 0-3.2] vs 3.6 [IQR, 0-5.1]; P = .02). Moreover, the triad of gastric primary tumor, tumor size greater than 10 cm, and SUVmax of 5.75 or less was associated with identification of PDGFRA-mutant GISTs.Conclusions and RelevanceIn this cohort study of patients with PDGFRA-mutant GISTs, the D842V-mutant GISTs were associated with an overall lower [18F]FDG uptake compared with other GIST subgroups. Therefore, the role of functional imaging with [18F]FDG-PET in this subset of GISTs may be limited and should be further explored for its potential prognostic and predictive value.