Multiparametric fully-integrated 18-FDG PET/MRI of advanced gastric cancer for prediction of chemotherapy response: a preliminary study

To investigate usefulness of multiparametric fully integrated 18-FDG PET/MRI in predicting treatment response after chemotherapy for unresectable advanced gastric cancers (AGCs). Eleven patients with unresectable AGCs underwent multiparametric 18-FDG PET/MRI examinations prior to chemotherapy. Perfusion parameters obtained via dynamic contrast-enhanced MRI, apparent diffusion coefficient values from diffusion-weighted images, and maximum standardized uptake values (SUVmax) from 18-FDG PET were measured. For parameters obtained from 18-FDG PET/MRI data, interobserver agreement was obtained using intraclass correlation coefficients (ICC) and chemotherapy response relationship was evaluated using the Mann-Whitney test and receiver operating characteristic analysis. After chemotherapy, six patients were classified into the responder group and five patients into the non-responder group. For all parameters, moderate to nearly perfect agreement was achieved (ICC = 0.452-0.911). K (trans) values (P = 0.018) and initial area under the curves (iAUCs) (P = 0.045) of gastric cancers were significantly higher in responder group than in non-responder group. The area under the curve was 0.917 for K (trans) and 0.867 for iAUC. However, SUVmax values were not significantly different between the two groups. Multiparametric approach using fully integrated 18-FDG PET/MRI was shown to be feasible for patients with unresectable gastric cancers. In addition, K (trans) and iAUC values can be used as early predictive markers for chemotherapy response. Multiparametric 18-FDG PET/MRI is feasible for patients with unresectable advanced gastric cancer K (trans) and iAUC were significantly higher in the responder group of patients K (trans) , iAUC can be utilized as early predictive markers for chemotherapeutic response