Changes in 18F-FDG tumor metabolism after a first course of neoadjuvant chemotherapy in breast cancer: influence of tumor subtypes

The aim of this study is to evaluate the impact of the different breast cancer subtypes on the tumor F-18-FDG uptake at baseline and on its changes after the first course of neoadjuvant chemotherapy (NAC). One hundred and fifteen women with newly diagnosed, large or locally advanced breast cancer undergoing NAC were included. Estrogen receptor (ER), progesterone receptor (PR) and HER2 status were used to define three major tumor subtypes: triple negative (TN) (ER-/PR-/HER2-), luminal (ER+ and/or PR+; HER2-) and HER2 positive (HER2+). Using Fluorine-18 fluorodeoxyglucose positron emission tomography, the tumoral standard uptake value (SUV) maximal index was measured at baseline and just before the second course of NAC. TN tumors presented the highest baseline SUV (11.3 +/- 8.5; P < 0.0001). The decrease of SUV after the first course of NAC (delta SUV) was significantly higher in TN and HER2-positive subtypes (-45% +/- 25% and -57% +/- 30%, respectively) than in luminal one (-19% +/- 35%; P < 0.0001). delta SUV was a predictive factor of the pathological complete response only in HER2-positive tumors (cut-off = -75%; P < 0.03) with an accuracy of 76%. The baseline F-18-FDG tumoral uptake but also its early response to NAC is different according to the immunohistological subtypes of breast cancer.