Apparent diffusion coefficients (ADC) in response assessment of transarterial radioembolization (TARE) for liver metastases of neuroendocrine tumors (NET): a feasibility study.

Maria Katharina Ingenerf,Karla-Maria Treitl,Christine Schmid-Tannwald,Jens Ricke,Homeira Karim,Nicola Fink,Harun Ilhan

doi:10.1177/02841851211024004

Abstract

BackgroundIn patients with hepatic neuroendocrine tumors (NETs) locoregional therapies such as transarterial radioembolization (TARE) are increasingly applied. Response evaluation remains challenging and previous studies assessing response with diffusion-weighted imaging (DWI) have been inconclusive.PurposeTo perform a feasibility study to evaluate if response assessment with quantitative apparent diffusion coefficient (ADC) in patients with liver metastases of NETs after TARE will be possible.Material and MethodsRetrospectively, 43 patients with 120 target lesions who obtained abdominal magnetic resonance imaging (MRI) with DWI 39±28 days before and 74±46 days after TARE were included. Intralesional ADC (ADCmin, ADCmax, and ADCmean) were measured for a maximum number of three lesions per patient on baseline and post-interventional DWI. Tumor response was categorized according to RECIST 1.1 and mRECIST.ResultsTARE resulted in partial remission (PR) in 23% (63%), in stable disease (SD) in 73% (23%), in progressive disease (PD) in 5% (7%) and in complete response (CR) in 0% (1%) according to RECIST 1.1 (mRECIST, respectively). ADC values increased significantly (P<0.005) after TARE in the PR group whereas there was no significant change in the PD group. Post-therapeutic ADC values of SD lesions increased significantly when evaluated by RECIST 1.1 but not if evaluated by mRECIST. Percentual changes of ADCmean values were slightly higher for responders compared to non-responders (P<0.05).ConclusionADC values seem to represent an additional marker for treatment response evaluation after TARE in patients with secondary hepatic NET. A conclusive study seems feasible though patient-based evaluation and overall survival and progression free survival as alternate primary endpoints should be considered.

Highlights

At the time of diagnosis, 70% of patients with neuroendocrine tumors (NETs) have metastases primarily affecting the liver [1]
The aim of the present study was to further analyze how apparent diffusion coefficient (ADC) values change after transarterial radioembolization (TARE) in hepatic metastases of NET, to evaluate if ADC changes correlate with tumor response according to RECIST 1.1 and modified version of the RECIST criteria (mRECIST), and whether a conclusive study will be possible
Both liver lobes were treated with TARE in 39 patients, the right lobe only was treated in four patients

Summary

Introduction

At the time of diagnosis, 70% of patients with neuroendocrine tumors (NETs) have metastases primarily affecting the liver [1]. Criteria for imaging response are traditionally based on changes in tumor size, most commonly according to the Response Evaluation Criteria In Solid Tumors (RECIST 1.1.); these criteria were initially developed to evaluate treatment response to cytotoxic therapies. Despite their broad use, growing evidence indicates that the evaluation of tumor size only is of limited value, especially when assessing the response to new treatment strategies [5,6]. Conclusion: ADC values seem to represent an additional marker for treatment response evaluation after TARE in patients with secondary hepatic NET. A conclusive study seems feasible though patient-based evaluation and overall survival and progression free survival as alternate primary endpoints should be considered

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