Purpose

To determine the feasibility of whole-body diffusion-weighted magnetic resonance imaging (WBDWI) for assessment of treatment response in aggressive non-Hodgkin lymphoma (NHL).

Introduction

Up to now, several researches have demonstrated that WBDWI was a valuable tool used for comprehensive tumor assessments in various malignant diseases. The purpose of this study was to assess the pre- and post-treatment ADC changes on WBDWI, using contrast enhanced CT as reference standard.

Method

Patients with NHL treated with standard chemotherapy underwent 1.5-T WBDWI and contrast enhanced CT scan before and after 2 cycles chemotherapy during treatment, using b-values of 0 and 800 s/mm² from which the apparent diffusion coefficient (ADC_min) was calculated. Patient follow-up (more than 12 months) was the reference standard. Volume and ADC_min per lesion (lymph node and organ lesions) on baseline and early phase during chemotherapy were measured. The assessment was based on the malignant lymphoma treatment efficacy evaluation criteria. Using the receiver operating characteristic (ROC) curve evaluate ADC values pre- and post- chemotherapy, and the changes of ADC values (△ADC= ADC_post – ADC_pre) to predict the efficacy at the end of the entire chemotherapy. Areas under the curve were compared by Hanley & McNeil. Categorical variables were tested with the Chi-square test or McNemar test.

WBDWI and CT examination

WBDWI scanned in a 1.5T MR scanner (GE MR 360 Optix). A single short EPI sequence was used to acquire diffusion images with the following parameters: axial plane, 30 slices with 7 mm thickness and -1mm gap, FOV = 40 cm×40 cm, matrix = 96×128, TR/TE = 5100/81.9 ms , b value = 800 s/mm², 4 averages. 3D-MIP and the black/white inversion post image processing technique were performed on ADW4.6 workstation. CT scanning was performed using a GE 64-slice spiral CT (GE Lightspeed VCT, Discovery CT 750 HD). Intravenous injection of non-ionic iodine contrast medium was using a high-pressure syringe, the dose was 90ml, the flow rate was 2.5ml/s, the slice thickness/spacing was 5/5mm.

Results

34 NHL patients were enrolled in this study (22 male, 12 female; aged 19-77 years; total 556 lesions, including 473 lymph nodes invaded). According to pathological type, there were 26 cases of diffuse large B cell lymphoma (277 lymph nodes), 2 cases of B small lymphocytic lymphoma (87 lymph nodes), 2 cases of precursor T lymphoblastic lymphoma (76 lymph nodes), 2 cases of MALT (3 lymph nodes), 1 case of follicular lymphoma (30 lymph nodes), and 1 case of anaplastic large B cell lymphoma (only with extranodal invaded), respectively. 3 cases were in stage I, 11 cases were in stage Ⅱ, 12 cases were in stage Ⅲ, 8 cases were in stage Ⅳ, respectively. 21 cases both had pre- and post-treatment WBDWI. The pre-treatment ADC_min was 0.833±0.225×10^-3mm²/s; the post-treatment ADC_min increased to 2.097±0.934×10^-3mm²/s, there was statistically significant difference between pre- and post- treatment ADC_min (t=-24.553，P=0.000) (Figure.1). The pre-treatment ADC_min in responding lesions was significantly different from non-responding lesions (AZ=0.716, P = 0.000) in early phase (2 circle) chemotherapy, the lesion which pre-treatment ADC_min ≤0.715 × 10^-3mm²/s, showed more progressive in early phase chemotherapy (Figure.2), but there was no predictive value for the end of entire chemotherapy (AZ=0.554, P = 0.161) (Figure.3). While the early phase post-treatment ADC_min and △ADC has predictive value for the end of entire chemotherapy, there was statistically significant difference between responding and non-responding lesions (AZ=0.792, P = 0.000; AZ=0.761, P = 0.000), the responding lesions show ADC_min ＞1.5×10^-3mm²/s (sensitivity 77.9%, specificity 77.5%) or △ADC ＞ 0.87×10^-3mm²/s (sensitivity 64.7%, specificity 85.9%).

Discussion and Conclusion

MRI is emerging as an efficient whole-body imaging modality combining sequences with adequate spatial and contrast resolution. DWI characterizes tissue by probing changes in random water molecule mobility related to differences in the tissue microstructure. Quantified by the ADC, allow viable tumors to be differentiated from necrosis and inflammation. Whole-body DWI with ADC mapping can show a persistent low ADC values of residual tumor after treatment and may help to assess the treatment response [1,2]. Responded well lesions showed a significantly higher post-treatment ADC and a higher ADC value changes (△ADC) compared with non-responding lesions. 1.5-T WBDWI with ADC quantification may enable early treatment assessment of aggressive NHL correctly and timely.

Acknowledgements

No acknowledgement found.

References

[1]De Paepe K, et al. Cancer Imaging, 2013, 13: 53-62.
[2]Chieh Lin, et al. Invest Radiol. 2011 May; 46(5):341-9.