Role of Diffusion Weighted Imaging in Assessment of Tumor Response After Loco-regional Therapy in Patients of Hepato-Cellular Carcinoma

Abstract

Background and Aim: Diffusion Weighted Imaging (DWI) has been found to be useful in liver mass characterisation. Its role in post-treatment evaluation has not been adequately explored. While dynamic contrast-enhanced magnetic resonance imaging (DCE—MRI) is the standard of evaluation for post-treatment response, DWI can potentially differentiate between viable and non-viable tissue and hence may be useful. This study was designed to evaluate the sensitivity and specificity of DWI in response assessment after loco-regional therapy for HCC. Methods: A prospective study was done between January 2009 and January 2017. Patients of HCC who presented to our liver clinic and undergoing loco-regional therapy [trans- arterial chemo-embolisation (TACE)/ablation techniques including radio-frequency ablation (RFA), percutaneous acetic acid injection (PAI)] were included. Four weeks post-treatment, DCE-MRI was performed using VIBE sequences to ascertain treatment response of index mass, based on m-RECIST criteria and DWI to look for presence/absence of diffusion restriction. DCE-MRI was the gold-standard. If partial response (PR) was detected on DCE-MRI, a repeat session of the earlier treatment was done followed by repeat DCE-MRI at 4 weeks (each evaluation being one observation). Results: HCC patients (n = 44) including 33 males, 11 females, having mean age 51.8 ± 14.6 years were included and underwent repetitive evaluation of 62 nodules. Post-therapeutic (54 TACE, 4 RFA and 4 PAI) response evaluation was done. DCE-MRI showed contrast enhancement in 15/62(24.2%) nodules (PR), while diffusion restriction was seen in 13/15(86.7%) of these nodules. No enhancement was seen in 47/62(75.8%) nodules (complete response), of which 37/47(78.7%) showed no restriction, while 10/47(21.3%) showed restricted diffusion. DWI thus showed a sensitivity of 86.7% and specificity of 78.7%. Conclusion: DWI shows good sensitivity and moderate specificity for assessing response in HCC after loco-regional therapy. Although DWI cannot be a standalone for post- treatment response assessment, it may be useful as an adjunct to DCE-MRI. The authors have none to declare.