Prognostic relevance at 5 years of the early monitoring of neoadjuvant chemotherapy using 18F-FDG PET in luminal HER2-negative breast cancer

Purpose The objective of this study was to evaluate, in the luminal human epidermal growth factor receptor 2 (HER2)-negative breast cancer subtype, the prognostic value of tumour glucose metabolism at baseline and of its early changes during neoadjuvant chemotherapy (NAC). Methods This prospective study included 61 women with hormone-sensitive HER2-negative breast cancer treated with NAC. F-18-Fluorodeoxyglucose (FDG) positron emission tomography (PET) was performed at baseline. Hepatic activity was used as a reference to distinguish between low metabolic and hypermetabolic tumours. In hypermetabolic tumours, a PET exam was repeated after the first course of NAC. The relative change in the maximum standardized uptake value of the tumour (Delta SUV) was calculated. Results Nineteen women had low metabolic luminal breast cancers at baseline, correlated with low proliferation indexes. Forty-two women had hypermetabolic tumours, corresponding to more proliferative breast cancers with higher Ki-67 expression (p = 0.017) and higher grade (p = 0.04). The median follow-up period was 64.2 months (range 11.5-93.2). Thirteen women developed recurrent disease, nine of whom died. Worse overall survival was associated with larger tumour size [> 5 cm, hazard ratio (HR) = 6.52, p = 0.009] and with hypermetabolic tumours achieving a low metabolic response after one cycle of NAC (Delta SUV < 16 %, HR = 10.63, p = 0.004). Five-year overall survival in these poor responder patients was 49.2 %. Overall survival in women with low metabolic tumours or hypermetabolic/good response tumours was 100 and 96.15 %, respectively. Conclusion In luminal HER2-negative breast tumours, tumour metabolism at baseline and changes after the first course of NAC are early surrogate markers of patients' survival. A subgroup of women with hypermetabolic/poorly responding tumours, correlated with poor prognosis at 5 years, can be identified early. These results may guide future studies by tailoring the NAC regimen to the metabolic response.