Soft tissue sarcoma: adding diffusion-weighted imaging improves MR imaging evaluation of tumor margin infiltration

Purpose To determine the added value of diffusion-weighted imaging (DWI) to conventional magnetic resonance (MR) imaging in assessment of tumor margin infiltration in soft tissue sarcoma (STS) at 3T. Materials and methods The institutional review board approved this retrospective study. Forty-five patients who underwent 3T MR imaging including DWI and were pathologically confirmed were included in this study. Two readers retrospectively scored conventional MR imaging alone. Then, they assessed a combination of conventional MR imaging and DWI. At pathology, margin infiltration was retrospectively reviewed by one pathologist blinded to MR findings. Areas under the curve (AUCs) of the receiver-operating characteristic curve were obtained for diagnostic performance. Interobserver agreement for the scoring of margin infiltration of STS was assessed with kappa statistics. Results Among 45 cases of STS, 33 had infiltrative tumor margin at pathology. Sensitivity, specificity, and accuracy of each reader were 100%, 17%, and 78%; 97%, 25%, and 78% on conventional MR imaging alone and 94%, 67%, and 87%; 94%, 42%, and 80% on conventional MR imaging combined with DWI. AUCs of conventional MR imaging combined with DWI were significantly higher than those of conventional MR imaging alone: 0.890 vs 0.678 ( p = .0123) and 0.846 vs 0.640 ( p = .0305) for each reader. Interobserver agreements of conventional MR imaging alone and conventional MR imaging combined with DWI were moderate to substantial ( κ = 0.646, κ = 0.496). Conclusion The addition of DWI to conventional MR imaging may improve specificity for assessing tumor margin infiltration in STS at 3T. Key Points • DWI has added value for assessment of tumor margin infiltration in soft tissue sarcoma. • Addition of DWI to conventional MRI at 3T may improve specificity. • Addition of DWI to conventional MRI may help orthopedic surgeon determine the extent of the resection margin .