18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) as early imaging biomarker of axillary sentinel lymph node (SLN) status in locally advanced node-positive breast cancer (NPBC) patients (pts) receiving neoadjuvant chemotherapy (NACT).

Abstract

1129 Background: Use of FDG-PET in the early evaluation of NACT for NPBC is currently under investigation. The aim of this study is to assess FDG-PET in NPBC pts receiving NACT in order to identify a subset of pts that can be spared axillary lymph node dissection (ALND) in case of response. Methods: All pts (period 2009-2011) had [cT2 (≥3cm)-T4, pN1-3], and no prior BC treatment. All pts received 8 cycles (cy) of NACT +/- trastuzumab. FDG-PET was performed at baseline and after 2 cy. After NACT, mastectomy with SLN and ALND was peformed. As primary endpoint, the change in maximum standardized uptake value (SUVmax) in the primary tumor (PT) and ALNs was compared with pathological response (Jonckheere-Terpstra test). Logistic regression was used to determine the predictive value of a 50% reduction in SUVmax on pathological response and SLN status. Results: Forty-one pts were evaluable for the primary endpoint and 31 pts had successful SN procedures. The median age was 49.8 years (range 27-75). Overall, 9.8% (4/41; 95% CI 2.7 – 23.1) of pts had progressive disease (PD), 7.3% (3/41 ; 95% CI 1.5 – 19.9 ) stable disease (SD), 53.7% (22/41; 95% CI 37.4 – 69.3) partial response (PR), and 21.9% (9/41; 95% CI 10.6 – 37.6) a complete pathological response (pCR). A linear trend existed between pCR and higher decreases in SUVmax of the PT site (p=0.008), but not with lymph node SUVmax (p=0.294). The odds of achieving a pCR, increased significantly when SUVmax of the PT decreased with >50% (OR 10.7; 95% CI 1.2 - 98.0; p=0.03), but not lymph node SUVmax (OR 4.75; 95% CI 0.82 - 27.5; p=0.08). Achieving a true negative SLN status was more likely with >50% reductions in PT SUVmax (OR 41.2; 95% CI 4.0 - 421.9; p= 0.002). A reduction of >50% in nodal SUVmax was not predictive of negative SLN status (OR 3.33; 95% CI 0.66 - 16.8; p=0.1). Conclusions: Early changes in PT metabolism imaged with FDG-PET after only 2 cy of NACT is a promising biomarker in the management of the axilla in NPBC. Molecular imaging of PT biology and to a lesser extent of axillary lymph nodes using FDG-PET warrants further study.