CD44 expression is predictive of poor prognosis in pharyngolaryngeal cancer: systematic review and meta-analysis

Pharyngolaryngeal cancer is one of the most common head and neck cancer worldwide, and the early diagnosis and prognosis prediction are still difficult because of lacking in reliable cell markers. Although the expression of CD44 has been reported to correlate with poor prognosis of pharyngolaryngeal cancer in most literatures, some controversies still exist. Since the limited patient numbers within independent studies, here we performed a meta-analysis to clarify the correlations between CD44 expression and clinicopathological features and prognosis in pharyngolaryngeal cancer. A search of PubMed, ISI Web of Science and China National Knowledge Infrastructure databases (up to June 2013) was performed. Nineteen studies with 1,405 patients met the inclusion criteria. The expression of pan-CD44, including all variant isoforms, was detected in 58.0% (14.1-79.2%) specimens, while CD44-v6 (variant isoform 6 of CD44) was expressed in 54.8% (12-79.2%). In pooled analysis, CD44 expression was significantly associated with larger tumor size (T category, RR (relative risk) = 1.21, 95% CI: 1.01-1.46), lymph nodes metastasis (N category, RR = 1.94, 95% CI: 1.38-2.73) and poor prognosis [3-year overall survival (OS): RR = 0.70, 95% CI: 0.53-0.91; 5-year OS: RR = 0.66, 95% CI: 0.66-0.94]. In the stratified analysis of CD44 isoforms, high expression of CD44-v6 was related with a poor 5-year OS rate (RR = 0.53, 95% CI: 0.37-077). We propose that CD44 expression is associated with tumor size, lymph node metastasis, and poor prognosis in pharyngolaryngeal cancer patients.