Tumor metabolism and blood flow as assessed by positron emission tomography varies by tumor subtype in locally advanced breast cancer.

PURPOSE 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. EXPERIMENTAL DESIGN Tumor subtype was defined by immunohistochemistry in 71 patients with locally advanced breast cancer undergoing NC. Subtype was defined as luminal [estrogen receptor (ER)/progesterone receptor (PR) positive], triple negative [TN; ER/PR negative, human epidermal growth factor receptor 2 (HER2) negative], and HER2 (ER/PR negative, HER2 overexpressing). Metabolic rate (MRFDG) and blood flow (BF) were calculated from PET imaging before 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% confidence interval, 9-156%) and average MRFDG/BF ratio was 53% greater in TN compared with luminal tumors (95% confidence interval, 9-114%; P<0.05 for both). Average BF levels did not differ by subtype (P=0.73). Most luminal tumors showed relatively low MRFDG and BF (and did not achieve pCR); high MRFDG was generally matched with high BF in luminal tumors and predicted pCR. This was not true in TN tumors. CONCLUSION The relationship between breast tumor metabolism and perfusion differed by subtype. The high MRFDG/BF ratio that predicts poor response to NC was more common in TN tumors. Metabolism and perfusion measures may identify subsets of tumors susceptible and resistant to NC and may help direct targeted therapy.