Comparative Analysis of Amide Proton Transfer and Diffusionweighted Imaging for Assessing Ki-67, p53 and PD-L1...

To evaluate amide proton transfer (APT) imaging for assessing Ki-67, p53 and PD-L1 status in bladder cancer (BC) and compare its diagnostic efficacy with that of diffusion-weighted imaging (DWI).

Consecutive patients suspected of BC were recruited for preoperative multiparametric MRI. APT signal was quantified by asymmetric magnetization transfer ratio (MTR_asym). MTR_asym and apparent diffusion coefficient (ADC) were measured by two radiologists, with interobserver agreement assessed. Spearman's correlation analyzed MTR_asym values and molecular markers. The Whitney U test evaluated MTR_asym and ADC variation based on molecular marker status. Optimal cutoff points were determined using area under the curve (AUC) analysis.

88 patients (72 ± 10 years; 77 men) with BC were studied. MTR_asym values were significantly correlated with Ki-67, p53 and PD-L1 levels (P < 0.05). Higher MTR_asym values were found in high Ki-67 expression BCs (1.89% [0.73%] vs. 1.23% ± 0.26%; P < 0.001), high p53 expression BCs (1.63% [0.56%] vs. 1.24% [0.56%]; P < 0.001) and positive PD-L1 expression BCs (2.02% [0.81%] vs. 1.48% [0.38%]; P < 0.001). Lower ADCs were found in high Ki-67 expression BCs (1.06 ×10^-3 mm²/s [0.32 ×10^-3 mm²/s] vs. 1.38 ×10^-3 mm²/s [0.39 ×10^-3 mm²/s]; P < 0.001). For p53 status, an MTR_asym threshold of 1.27% had 95% sensitivity, 60% specificity, and AUC of 0.781. For PD-L1 status, a 1.90% threshold had 88% sensitivity, 92% specificity, and AUC of 0.859.

APT may significantly enhance the preoperative assessment of BC aggressiveness and inform targeted immunotherapy decisions, with performance superior to DWI.