Non-enhanced abbreviated MRI as a periodic surveillance protocol for colorectal liver metastases compared with contrast-enhanced CT: a prospective observational study

Background: Adopting an appropriate noninvasive radiological method is crucial for periodic surveillance of liver metastases in colorectal cancer (CRC) patients after surgery, which is closely related to clinical management and prognosis. This study aimed to prospectively enroll stage II-III CRC patients for the surveillance of liver metastases and compare the diagnostic performance of contrast-enhanced CT (CE-CT) and non-enhanced abbreviated MRI (NE-AMRI) during this process. Methods: 587 CRC patients undergoing radical resection of the primary tumor were evaluated by 1 to 3 rounds of surveillance tests, consisting of abdominal CE-CT and contrast-enhanced MRI (CE-MRI) within 7 days at 6-month intervals. Subsequently, images of NE-AMRI were extracted from the CE-MRI examination, and paired CE-CT and NE-AMRI analysis were performed. The lesion-based detection rates between two protocols were compared, and a subgroup analysis was performed in lesions with a size of ≤10 mm. The patient-based sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, and the areas under the curves (AUCs) of CE-CT and NE-AMRI in each round were evaluated. Finally, the relationship between the diagnostic accuracy of two protocols and characteristics of patients was explored. Results: The lesion-based detection rates of NE-AMRI in three rounds were all significantly higher than those of CE-CT ( P < 0.001, P < 0.001, P = 0.003, respectively). In the subgroup analysis of lesions ≤ 10 mm, NE-AMRI also performed better than CE-CT ( P < 0.001, P = 0.002, P = 0.005, respectively). The patient-based sensitivities, specificities, NPVs, and PPVs of NE-AMRI were higher than those of CE-CT in three rounds of surveillance. The AUCs for NE-AMRI were all significantly better than those for CE-CT in each round ( P = 0.015, P = 0.045, P = 0.009, respectively). Furthermore, patient BMI and fatty liver disease had impacts on the diagnostic accuracy of the CE-CT protocol, but not on the NE-AMRI protocol. Conclusion: NE-AMRI may be a promising periodic surveillance tool for CRC patients after surgery to increase diagnostic accuracy of liver metastases, developing personalized clinical management and improving prognosis, simultaneously avoiding side effects associated with ionizing radiation and contrast agents.