FDG-PET/CT and MRI for Evaluation of Pathologic Response to Neoadjuvant Chemotherapy in Patients With Breast Cancer: A Meta-Analysis of Diagnostic Accuracy Studies.

Introduction: This study compared the diagnostic test accuracy of magnetic resonance imaging (MRI) with that of (18)F-fluoro-2-glucose-positron emission tomography/computed tomography (FDG-PET/CT) imaging in assessment of response to neoadjuvant chemotherapy (NAC) in breast cancer.
Methods: A systematic search was performed in PubMed and EMBASE (last updated in June 2015). Studies investigating the performance of MRI and FDG-PET or FDG-PET/CT imaging during or after completion of NAC in patients with histologically proven breast cancer were eligible for inclusion. We considered only studies reporting a direct comparison between these imaging modalities to establish precise summary estimates in the same setting of patients. Pathologic response was considered as the reference standard. Two authors independently screened and selected studies that met the inclusion criteria and extracted the data.
Results: A total of 10 studies were included. The pooled estimates of sensitivity and specificity across all included studies were 0.71 and 0.77 for FDG-PET/CT (n = 535) and 0.88 and 0.55 for MRI (n = 492), respectively. Studies were subgrouped according to the time of therapy assessment. In the intra-NAC setting, FDG-PET/CT imaging outperformed MRI with fairly similar pooled sensitivity (0.91 vs. 0.89) and higher specificity (0.69 vs. 0.42). However, MRI appeared to have higher diagnostic accuracy than FDG-PET/CT imaging when performed after the completion of NAC, with significantly higher sensitivity (0.88 vs. 0.57).
Conclusion: Analysis of the available studies of patients with breast cancer indicates that the timing of imaging for NAC-response assessment exerts a major influence on the estimates of diagnostic accuracy. FDG-PET/CT imaging outperformed MRI in intra-NAC assessment, whereas the overall performance of MRI was higher after completion of NAC, before surgery.
Implications for Practice: The timing of therapy assessment imaging exerts a major influence on overall estimates of diagnostic accuracy. (18)F-fluoro-2-glucose-positron emission tomography (FDG-PET)/computed tomography (CT) imaging outperformed magnetic resonance imaging (MRI) in intra-neoadjuvant chemotherapy assessment with fairly similar pooled sensitivity and higher specificity. However, MRI appeared to be more accurate than FDG-PET/CT in predicting pathologic response when used in the post-therapy setting.
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