Abstract P2-09-31: Circulating Ang-2 Predicts Distant Breast Cancer Recurrence in WHEL Study
Authors: Pierce JP , Dominick S , Natarajan L , Flatt S , Patterson RE , Rana BK , Parker BA. 
Published: April 2011

Background: The cytokine ,Angiopoietin-2 (Ang-2), is associated with breast cancer invasion and metastasis in preclinical models and in clinicopathologic studies of breast cancer. Anti-angiogenic therapy (bevacizumab plus chemotherapy) has anti-tumor activity in metastatic breast cancer patients. Circulating Ang-2 may serve as a biomarker for distant breast cancer recurrence. Multiple small studies suggest that circulating IL-6, a cytokine that promotes migration and invasion of breast cancer cells, may also predict recurrence. The Women's Healthy Eating and Living (WHEL) study has a unique data set with serial blood samples, some within 6 months of recurrence, which allowed a focused test of circulating factors and distant recurrence. Using a standard 30 cytokine array chosen because it included both Ang-2 and IL-6, we examined associations between cytokine markers and short-term distant breast cancer recurrence.

Methods: Fasting bloods were collected at 5 time points during the 6 year intervention of the WHEL study. There were 100 women who provided this sample within 6 months of diagnosis of recurrent metastatic cancer (oncologist confirmed). We tightly matched 100 non-recurrers from the main study who provided blood at the equivalent study time point. Matching variables included follow-up interval, age, clinical stage of the original tumor and enrollment site (WHEL had 7 sites). 30 chemo/cytokines were measured in each plasma sample using the Quantibody® Human Angiogenesis Array 2 (RayBiotech, Inc., Norcross, GA). Cytokine concentrations were log transformed. We used paired t-tests (P&lt;0.20) to remove cytokines that did not differ between groups. Cox proportional hazard models were used to identify cytokines predictive of breast cancer recurrence after adjustment for covariates. Each Cox model was stratified by case/control pair number and contained one cytokine. The hazard ratio (95% Confidence Interval [CI]) was the measure of association per unit log transformed cytokine concentration. In further exploratory analysis, we applied a tree-based recursive partitioning method, Classification and Regression Trees (CART), which identifies high or low risk sub-group thresholds by sequentially choosing the most predictive marker. Results: The groups were successfully matched as only tumor grade met the criteria for inclusion as a covariate in the final models. Ang-2 and IL-6 differed between cases and controls in the paired t-test analyses, as did 3 other cytokines: RANTES, HB-EGF, and MCP-1. However, in the Cox proportional hazard models, only Ang-2 (HR=2.32; 95% C.I.= 1.16-4.66, p=0.02) reached statistical significance, although IL-6 was borderline significant (HR=1.52; 95% C.I.=0.94-2.47; p=0.09). Ang-2 was also the first marker chosen by the CART program and it identified 15 of the 200 in the study sample (8%) as protected (87% did not recur) and these were characterized with Ang-2 concentrations below 12.3 ng/ml. Discussion: This efficient nested case-control study tested whether circulating cytokines in the fasting blood predicts the onset of a distant recurrence within the next 6 months. This exploratory analysis identified Ang-2 as having prognostic value for metastatic breast cancer, but IL-6 was not a strong predictor in this study.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-09-31.