Early prediction of pathological complete response in luminal B type neoadjuvant chemotherapy-treated breast cancer patients: Comparison between interim 18 F-FDG PET/CT and MRI

Purpose The aim of this study is to justify the effectiveness of interim PET/computed tomography (CT) for predicting pathological complete response (pCR) in luminal B type breast cancer patients and to compare the diagnostic performance of interim PET/CT and MRI. Materials and methods Twenty-one patients with neoadjuvant chemotherapy (NAC)-treated luminal B type breast cancer were included. All patients underwent PET/CT and MRI at baseline and interim (mid-point). Breast surgery was performed after completion of NAC. Maximum standardized uptake values (SUV max) of breast malignant lesions in each PET/CT scan were acquired in each patient. The metabolic response was calculated as follows: ΔSUV (%)=(baseline SUV max -interim SUV max)/baseline SUV max ×100 (%). In MRI, the relative size change was calculated as follows: Size change (%)=longest diameter interim MRI-longest diameter baseline MRI/longest diameter baseline MRI×100 (%). pCR was concluded through the final pathologic specimen after breast surgery. The receiver-operating characteristic analysis was used as a statistical method. Results Of 21 patients, seven achieved a pCR after surgery. In PET/CT, an optimal cut-off ΔSUV (%) of 69.0% was proposed with a sensitivity of 85.7% and a specificity of 100% (P<0.0001). In MRI, an optimal cut-off size change (%) was 38.2% with a sensitivity of 64.3% and a specificity of 71.4% (P=0.29). The area under the curve was 0.92 and 0.65, respectively. PET/CT presented better predictability of the pCR than MRI (P=0.04). Conclusion In luminal B type NAC-treated breast cancer patients, it is possible to use PET/CT as an early surrogate marker for predicting pCR and it is significantly more predictable for pCR than MRI.