Use of PET to assess tumor metabolism and blood flow by tumor subtype in locally advanced breast cancer.

600 Background: Dynamic positron emission tomography (PET) imaging can identify patterns of breast cancer metabolism and perfusion in patients receiving neoadjuvant chemotherapy (NC) that are predictive of response. This analysis examines tumor metabolism and perfusion by tumor subtype. Methods: Tumor subtype was defined by immunohistochemistry (IHC) in 71 patients with locally advanced breast cancer (LABC) undergoing NC. Subtype was defined as luminal (ER/PR positive), triple-negative (TN; ER/PR negative, HER2 normal) and HER2 (ER/PR negative, HER2 over-expressing). Metabolic rate (MRFDG) and blood flow (BF) were calculated from PET imaging prior to NC. Pathologic complete response (pCR) to NC was classified as pCR versus other. Results: Twenty-five (35%) of 71 patients had TN tumors, 6 (8%) were HER2 and 40 (56%) were luminal. MRFDG for TN tumors was on average 67% greater than for luminal tumors (95% CI 9%-156%), and average MRFDG/BF ratio was 53% greater in TN compared to luminal tumors (95% CI 9%-114...