The added value of the visual analysis of DWI in post-surgery follow-up of soft tissue sarcoma of the extremities: do we really need ADC?

Abstract

Introduction MRI has a fundamental role in the follow-up of soft tissue sarcomas (STSs). However, the differentiation of recurrences/residual disease from post-surgical changes is a complex task, with a central role for the radiologist. Materials and methods We retrospectively evaluated 64 post-surgery MRI for extremities STSs. MR protocol included DWI (b = 0, 1000). Two radiologists were asked to consensually evaluate: presence/absence of tumoral nodules, lesion conspicuity, imaging diagnostic confidence, ADC values, and DWI overall image quality. The gold standard was histology or MR follow-up. Results Thirty-seven lesions in 29/64 patients were confirmed as local recurrence or residual disease (n = 16 ≤ 1 cm) with 1 MR false positive. On DWI, the conspicuity of the proved tumor lesions resulted excellent in 29/37, good in 3/37 and low in 5/37, higher than conventional imaging. A statistically significant higher diagnostic confidence of DWI compared to conventional imaging (p < 0.001) and DCE (p = 0.009) was observed. In the 37 histologically confirmed lesions, mean ADC value was 1.31 × 10–9 m2/s. Overall scar tissues mean ADC was 1.70 × 10–9 m2/s. DWI quality resulted adequate in 81% and unsatisfactory in 5%. Conclusions In this highly heterogeneous group of tumors, the role of ADC seems to be limited. Based on our experience, looking at DWI images makes the lesions promptly and easily detectable. This technique gives less deceptive findings making the reader more confident in detecting/excluding tumoral tissue; the main drawback is the image quality and the lack of standardization.

Magnetic Resonance Imaging and Its Molecular Probes in Evaluating the Response to Tumor Treatment

“…Using ADC values, the noticeable therapeutic efficacy of Gd@HbCe6-PEG nanoparticles was quantitatively confirmed at 6 h after PDT, much earlier than that (day 2 post-PDT) evaluated by structural MRI. Stroeder et al [29] showed that the patients with a good tumor response had higher ADC values than non-responders, confirming that DWI can be a useful method for more accurate assessment of tumor response and the ADC values can be used as prognostic markers. However, the DWI signal and ADC values are strongly influenced by the scan parameters, which have not been standardized, and the optimal scanning parameters are not uniform from site to site, leading to differences in results obtained in similar studies [30].…”