Synopsis

Keywords: Pelvis, CEST & MT, cervical cancer

What are the values of three-dimensional amide proton transfer (APT) imaging and glucose-chemical exchange saturation transfer (glucoCEST) in WHO grading and staging of cervical cancer? We performed 3D-APT, 3D-glucoCEST, and DWI scans in 19 cervical cancer cases. APT signal intensity（SI）, and GlucoCEST SI could distinguish high-grade from low-grade; GlucoCEST SI can differentiate early (<IIB) from advanced (≥IIB) cervical cancer. Both APT and glucoCEST can be used for the preliminary evaluation of cervical cancer, but glucose CEST has advantages in the evaluation of cervical cancer grading and staging.

Introduction

Chemical exchange saturation transfer (CEST) is a novel magnetic resonance molecular imaging technique. CEST imaging saturates the exchangeable material by specific saturation pulses, so that the exchangeable material is exchanged with the water substrate, and then indirectly reflects the content of the exchangeable material by detecting the change in signal intensity of the water. The most established application of CEST is amide proton transfer weighted imaging (APTWI), which enables the non-invasive detection of free proteins and peptide molecules in the cytoplasm. Also, APTWI is affected by pH, and the APT effect becomes more pronounced as the pH increases. It has been found that APT can be used as a non-invasive biomarker to assess prognostic factors such as the staging of cervical cancer (1). GlucoCEST imaging is able to detect glucose levels indirectly. Xu et al.(2) used this principle to detect the presence of glucose concentrations in glioma lesions. And a previous study found good spatial agreement between [18]F-FDG autoradiography and glucoCEST images observed in colo-cervical tumor models(3). However, the value of glucoCEST in cervical cancer tumor assessment has not been reported in any study. The purpose of this study was to analyze the value of 3D-glucoCEST in cervical cancer tumor grading and staging, and to compare it with 3D-APT.

Methods

19 patients who underwent 3D-APT, 3D-glucoCEST, and DWI and had pathological findings of cervical cancer were included, The APT SI was defined as MTRasym (3.5 ppm) and the glucoCEST SI was defined as 1.2 ppm of magnetization transfer asymmetry MTRasym (1.2 ppm). Apparent diffusion coefficient (ADC) plots were generated using b values of 0, and 1000 s/mm2. The volume of interest (VOI) was delineated and the SI of ATP, glucoCEST, and ADC values of DWI were calculated. The differences in the values of each parameter between the high-grade (G3) and low-grade (G1+G2) tumor groups, and between the early (<IIB) and advanced (≥IIB) stage groups were compared and analyzed separately. Student’s t-test, Mann-Whitney U test, receiver operating characteristics (ROC) analysis, and Delong analysis were used for statistical analysis.

Result

The high-grade group of cervical cancer exhibited higher APTw SI, glucose CEST SI and lower ADC values. APTw SI, and glucoCEST SI all showed a positive correlation with tumor grade (r=0.431 and 0.652) The AUCs of 3D-APTw SI, 3D-glucoCEST SI, and ADC in distinguishing high-grade and low-grade cervical cancer were 0.778, 0.836, and 0.812, respectively. AUC (glucose CEST) > AUC (ADC) (p < 0.05), AUC(ADC) > AUC(APT) (p < 0.05), and no statistical difference between AUC (glucose CEST) and AUC(ADC). Advanced cervical cancer exhibits higher glucose CESTSI, and lower ADC values than early-stage tumors. AUC (glucoCEST) and AUC (ADC) were 0.682 and 0.591, respectively, with no statistical difference between them. There was no statistically significant difference in APTSI between early and advanced stage cervical cancer.

Discussion

It is generally believed that APTw SI responds to the mobile protein and peptide content within the tumor(4). In this study, ATPw SI was higher in the high-grade group than in the low-grade group, and ATPw SI was significantly and positively correlated with the grade of the tumor, and These are similar to the results of a previous study(1). The reason for this may be that high-grade cervical cancer tumors have higher cell density and more pronounced nuclear indiscipline leading to more protein and peptide production or release(5). The glucoCEST SI indirectly reflected the tissue glucose content. In this study, the glucoCEST SI was higher in the high-grade cervical cancer group than in the low-grade group, and also positively correlated with tumor grade. This may be due to higher glucose uptake due to the high proliferation of high-grade tumors. In addition, the advanced cervical cancer group had higher glucoCEST SI, which was similar to the results of previous studies in which PET/MR parameters MTV and TLG were used to assess cervical cancer staging(6), and this may be due to the fact that advanced cervical cancer usually has large tumor size and increased cell density, which requires more energy expenditure and leads to glucose accumulation.

Conclusion

Both 3D-APT and 3D-glucoCEST can be used for the preliminary evaluation of cervical cancer, but glucoCEST has advantages in the evaluation of cervical cancer grading and staging.

Acknowledgements

No acknowledgement found.