Sensitivity and specificity of amide proton transfer-weighted imaging for assessing programmed death-ligand 1 status in non-small cell lung cancer: a comparative study with intravoxel incoherent motion and (18)F-FDG PET

BACKGROUND: Noninvasive assessment of programmed death-ligand 1 (PD-L1) expression status in non-small cell lung cancer (NSCLC) is necessary. This study arm to investigate the value of 2-[(18)F]-fluoro-2-deoxy-D-glucose positron emission tomography ((18)F-FDG PET), diffusion-weighted imaging (DWI), intravoxel incoherent motion (IVIM), and amide proton transfer-weighted imaging (APTWI) in the assessment of PD-L1 status in NSCLC. METHODS: This is a prospective diagnostic study. A total of 76 patients with NSCLC underwent chest (18)F-FDG PET/magnetic resonance imaging (MRI). Parameters maximum standardized uptake value (SUV(max)), quantitate the metabolic tumor volume (MTV), total lesion glycolysis (TLG), apparent diffusion coefficient (ADC), diffusion coefficient (D), pseudo diffusion coefficient (D*), and perfusion fraction (f), and magnetization transfer ratio asymmetry at 3.5 ppm [MTRasym (3.5 ppm)] from (18)F-FDG PET, DWI, IVIM, and APTWI, respectively, were compared. The optimal combination of parameters was investigated using logistic regression models and evaluated by area under the receiver operating characteristic (ROC) curve (AUC). The bootstrap with 1,000 samples was used for model validation. RESULTS: SUV(max), MTV, TLG, and MTRasym (3.5 ppm) were higher and D and f were lower in PD-L1 positive NSCLC than in PD-L1 negative NSCLC (all P<0.05). Logistic analysis showed that the combination of MTRasym (3.5 ppm), D, and SUV(max) had the strongest predictive value for the differentiation of PD-L1 positive and PD-L1 negative NSCLC [AUC, 0.946; 95% confidence interval (CI): 0.869–0.985; sensitivity, 85.29%; specificity, 91.67%; P all <0.001]. The verification model showed the combination of MTRasym (3.5 ppm), D, and SUV(max) had the strongest predictive value, and its ROC curve and calibration curve showed good accuracy (AUC, 0.919, 95% CI: 0.891–0.937) and consistency. CONCLUSIONS: Multi-parametric (18)F-FDG PET/MRI is beneficial for the non-invasive assessment of PD-L1 status in NSCLC patients, and the combination of SUV(max), D, and MTRasym (3.5 ppm) may serve as a prognostic biomarker to guide immunotherapy.