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

Objective: 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.

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).

Conclusions: 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.