Carbonic anhydrase IX is a new independent prognostic marker in pre-menopausal breast cancer patients with 1 to 3 positive lymph nodes
Authors: Donal J. Brennan, Asa Kronblad, Karin Jirstrom, Goran Landberg, Michael J. Duffy, William M. Gallagher, Sallyann L. O Brien
Journal: Cancer Research (2006)

3608   * These authors contributed equally to this work;  † Corresponding author: william.gallagher@ucd.ie Hypoxia in breast cancer is associated with poor prognosis and down-regulation of the estrogen receptor (ER), with this potentially affecting the treatment efficiency of anti-estrogens. Carbonic anhydrase IX (CA IX) is a hypoxia-inducible gene regulated by HIF-1α and has been associated with poor outcome in many epithelial cancers, including breast cancer. Previous studies have been carried out on mixed cohorts of pre- and post-menopausal patients with locally advanced disease and varying treatment regimens. Here, we aimed to establish the true prognostic and predictive role of CA IX in pre-menopausal breast cancer. We analyzed CA IX expression using immunohistochemistry in a cohort of 400 pre-menopausal, stage II breast cancers arranged in a tissue microarray (TMA). The patients had participated in a randomized control trial comparing 2 years of tamoxifen to no adjuvant systemic treatment. All patients with lymph node positive disease received locoregional radiotherapy and the median follow-up was 13.9 years. The predictive role of CA IX regarding adjuvant tamoxifen treatment effect was studied in the treatment arm, whilst pure prognostic information was obtained from untreated control patients. CA IX was scored as positive in 11% of the tumors, and was exclusively expressed in ductal and medullary tumors. CA IX expression correlated positively with tumor size, and grade, as well as HIF-1α, Ki-67, Cyclin E, and Cyclin A2 expression and negatively with Cyclin D2, ER and progesterone receptor expression. CA IX expression did not correlate with HER2 overexpression or amplification, nor with VEGF-A or VEGFR2 expression. Taking the entire cohort, CA IX was associated with a reduced relapse-free survival (p = 0.0316), overall survival (p = 0.0216), breast cancer-specific survival (p = 0.005) and metastasis-free survival (p = 0.003). Expression of CA IX was not associated with a difference in tamoxifen response. In the control arm, CA IX was associated with worse outcome. Subgroup analysis revealed that CA IX was associated with reduced breast cancer specific survival in patients with one to three positive lymph nodes (p = 0.0134). Cox multivariate analysis, including standard prognostic markers, revealed that CA IX was the only independent prognostic marker of breast cancer-specific survival (Hazard Ratio 3.2, 95% Confidence Intervals 1.15-9.13; p = 0.027) in patients within this subgroup. These findings suggest that CA IX is an independent marker in patients with one to three positive lymph nodes. As all of these patients received locoregional radiotherapy, inhibition of CA IX may be a useful method of increasing the radiosensitivity of such tumors. Funding is acknowledged from the Health Research Board of Ireland, Cancer Research Ireland, Enterprise Ireland, and the BACR.