Comparison of magnetic resonance imaging and ⁶⁷gallium scintigraphy in the evaluation of posttherapeutic residual mediastinal mass in the patients with Hodgkin's lymphoma

Abstract 

Introduction

Detection of residual disease following the completion of primary treatment in Hodgkin's lymphoma (HL) patients diagnosed with mediastinal tumor mass has an exceptional importance in the assessment of therapeutic response. Magnetic resonance imaging (MRI) and ⁶⁷gallium (⁶⁷Ga) scintigraphy can be used to identify active tumor tissue in the mediastinal residuum.

Aims

To evaluate: the accuracy of MRI and ⁶⁷Ga scintigraphy in the prediction of clinical HL relapse/progression; congruence of findings and the probability of mediastinal disease relapse/progression regarding to the detection of active/inactive tissue by both imaging methods.

Materials and methods

Thirty HL patients with abnormal mediastinal tissue following the completion of primary treatment were examined by MRI and ⁶⁷Ga scintigraphy. Positive findings were: high signal intensity on unenhanced T2-weighted images on MRI and the abnormal accumulation of gallium on scintigraphy or SPECT. These findings were compared with the clinical follow-up.

Results

Sensitivity, specificity, accuracy, positive and negative predictive values were: 75.0%, 96.2%, 93.3%, 75.0%, 96.2% in MRI and 50.0%, 88.5%, 83.3%, 40.0%, 92.0% in ⁶⁷Ga scintigraphy. Discrepant results concerning the mediastinal tissue activity were found in 3 of 30 patients (10%). No statistically significant differences were found between both imaging methods in sensitivity, specificity and accuracy. Estimated 2-years progression free survival (PFS) for patients without and with active residual mediastinal tissue by MRI was 96% and 25% (p=0.0001), respectively. The probability of 2-years PFS in the cases with negative and positive findings on ⁶⁷Ga scintigraphy was 92% and 60% (p=0.026), respectively.

Conclusion

Although MRI showed better results than ⁶⁷Ga scintigraphy in the assessment of residual mediastinal tissue activity in HL patients after primary treatment, the difference between these methods was not statistically significant. Both methods could be included in the standard restaging protocol.

Keywords: Hodgkin's lymphoma, Mediastinum, Magnetic resonance imaging, Gallium scintigraphy