Is diffusion-weighted MRI sufficient for follow-up of neuroendocrine tumour liver metastases?

•DWI showed excellent agreement for liver lesion measurement with HSC.•Mean difference between DWI measurements and HSC was between 0.01 – 0.08 cm.•Weighted Kappa statistic was between 0.49 and 0.86, depending on b-value and reader.•DWI can potentially be used to restage hepatic disease in patients with NET metastases.•An MRI without contrast costs less than an MRI with hepatocyte specific contrast.

AimTo assess if diffusion-weighted imaging (DWI) alone could be used for follow-up of neuroendocrine hepatic metastases.Material and methodsThis was a retrospective study, approved by the institutional review board. Twenty-two patients with neuroendocrine liver metastases who had undergone more than one liver magnetic resonance imaging (MRI) examination, (including DWI and using hepatocyte-specific contrast medium) were evaluated. Up to five metastases were measured at baseline and at each subsequent examination. The reference standard measurement was performed on the hepatocyte phase by one reader. Three independent readers separately measured the same lesions on DWI sequences alone, blinded to other sequences, and recorded the presence of any new lesions.ResultsThe longest diameters of 317 liver metastases (91 on 22 baseline examinations and a further 226 measurements on follow-up) were measured on the reference standard by one reader and on three b-values by three other readers. The mean difference between DWI measurements and the reference standard measurement was between 0.01–0.08 cm over the nine reader/b-value combinations. Based on the width of the Bland and Altman interval containing approximately 95% of the differences between the reader observation and the mean of reference standard and DWI measurement, the narrowest interval over the nine reader/b-value combinations was −0.6 to +0.7 cm and the widest was −0.9 to 1 cm. In the evaluation of overall response using Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria, the weighted kappa statistic was between 0.49 and 0.86, indicating moderate-to-good agreement between the reference standard and DWI.ConclusionThe visualisation and measurement of hepatic metastases using DWI alone are within acceptable limits for clinical use, allowing the use of this rapid technique to restage hepatic disease in patients with neuroendocrine metastases.