Predicative value of [18F]-FDG PET scan for pathological complete response to neoadjuvant chemotherapy in breast cancer

Abstract

505 Background: To evaluate, in breast cancer patients treated by neoadjuvant chemotherapy, the early predictive value of the FDG uptake decrease for the assessment of the pathological complete response (pCR). Methods: Forty seven women with non metastatic with conventional imaging, non inflammatory, large or locally advanced breast cancer were included. Pathological tumour regression determined on surgical resection specimens served as the gold standard for the assessment of the neoadjuvant chemotherapy response. According to the Sataloff classification, patients were classified in two groups: patients with a pathological complete response (pCR) and patients with a pathological non complete response (non pCR). FDG uptake of breast lesions was evaluated before and after the first course of neoadjuvant chemotherapy, using Standard Uptake Value maximum (SUV) corrected by body surface area and glycaemia. Relations between baseline [18F]-FDG uptake and clinical, histopathological and biological parameters were assessed by Mann-Whitney test. Predictive value of the FDG decrease for the assessment of the pCR was studied with logistic regression analysis. Results: An elevated baseline SUV was found independently associated with a high mitotic activity (p<0.002), tumour grading (p<0.004), high score of nuclear pleomorphism (p= 0.03) and positive hormonal receptor status (p<0.005). After completion of chemotherapy, 11 (23%) of the 47 breast tumours examined at surgery showed a pCR while 36 (77%) showed a non pCR. The relative decrease (ΔSUV) after the first course of neoadjuvant chemotherapy was significantly greater in the pCR group than in the non pCR group (p< 10-4). A SUV decrease of 85.4% ± 21.9% in pCR patients versus 22.6% ± 36.6% in non pCR patients was found. ΔSUV<-60% predicted pCR with an accuracy of 87%. With multivariate logistic regression analyses, ΔSUV<-60% was the only predictive factor of the pCR Conclusions: In breast cancer patients treated by neoadjuvant chemotherapy, the FDG uptake decrease, after only one course of treatment, is an early and powerful predictor of the pCR. No significant financial relationships to disclose.