Carbonic anhydrase-9 expression in head and neck cancer: a meta-analysis

The purpose of the study was to compare CA-9 positivity versus CA-9 negativity in head and neck malignancies and to correlate levels of CA-9 with tumor grade, size, and nodal status. Overall and disease-free survival were also compared for CA-9 positive and negative tumors. A literature search was performed using Medline, Embase, Ovid and Cochrane databases for studies between 1990 and 2009. Carbonic anhydrase IX, CA IX, CA-9, head and neck, and survival were used as search terms. Random-effect meta-analytical techniques were conducted for outcome measures of overall survival and disease-free survival. Sixteen studies matched the selection criteria, reporting on 1,470 patients. Eight hundred and forty two specimens were reported as being CA-9 positive or negative: 512 (60.81%) were CA-9 positive and 330 (39.19%) were CA-9 negative. Nine hundred and eighty specimens had levels of CA-9 expression recorded: 547 (55.82%) had high levels of CA-9 and 433 (44.18%) had low CA-9 levels. Survival was significantly reduced if the tumor was positive for CA-9 (P < 0.0001). Disease-free survival is significantly reduced in patients with CA-9 positive (P = 0.0008) head and neck malignant tumors. The presence of CA-9 in head and neck malignant tumors is associated with reduced overall survival and disease-free survival.