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

Abstract

11007 Background: To evaluate, in the luminal breast cancer subtype, the prognostic value of tumor glucose metabolism at baseline and of its changes after one cycle of neoadjuvant chemotherapy (NAC). Methods: This prospective study included 61 women with immunophenotypically defined luminal HER2-negative breast cancer treated with NAC. 18F-FDG PET was performed at baseline. Hepatic activity was used as a reference to distinguish between low-metabolic and hypermetabolic tumors. In hypermetabolic tumors, a PET exam was repeated after the first course of NAC. The relative change in the maximal Standardized Uptake Value of the tumor (ΔSUV), corresponding to the metabolic response, was calculated. Results: Forty-two women had hypermetabolic tumors at baseline, corresponding to more proliferative breast cancers with higher Ki-67 expression (p=0.017) and higher grade (p=0.04). Nineteen women had low-metabolic tumors with lower proliferation indexes. Worse overall survival was associated with larger tumor size (>5cm, HR=6.52, P=0.009) and with hypermetabolic tumors achieving a low metabolic response after one cycle of NAC (ΔSUV<16%, HR=10.63, P=0.004). Five-year overall survival in these poor-response patients was 49.22% (95% CI=[14.76%-76.90%]). In contrast, overall survival in women with low-metabolic tumors or hypermetabolic/good-response tumors (ΔSUV≥16%) was good, 100% and 96.15%, respectively (95% CI=[75.69%-99.45%]). Conclusions: In luminal HER2-negative breast tumors, tumor metabolism at baseline and changes after the first course of NAC are surrogate markers of patients’ survival. A subgroup of women with hypermetabolic/bad-responding tumors correlated with poor prognosis can be identified. These results may create the ability to tailor the NAC regimen to the metabolic response at an early stage.