Clinicopathologic significance of cyclooxygenase-2 overexpression in esophageal squamous cell carcinoma

Background. Esophageal cancer is one of the most aggressive malignancies in the world, and whether multiple therapeutic modalities could improve long-term survival remains controversial. Recent studies have shown an increase of cyclooxygenase-2 (COX-2) expression in various malignancies, but its clinicopathologic role in esophageal squamous cell carcinoma (ESCC) remains unclear. Methods. From 1993 to 1997, tissue samples from 96 patients with ESCC who underwent esophagectomy at our institution were collected for analysis. Cyclooxygenase-2 expression was examined by immunohistochemical staining, and further confirmed by Western blot analysis on six frozen tissues. Clinicopathologic data were analyzed to verify the significance. Results. Cyclooxygenase-2 immunoreactivity was detected in 59 of 96 ESCC specimens (61%), and COX-2 overexpression (COX-2 high) was observed in 49% (47 of 96) of ESCCs. Statistical differences between COX-2 high and COX-2 low were found with respect to the status of distant metastasis (M factor) (p = 0.035) and tumor stage (p = 0.04). The survival was not significantly different between patients with and without COX-2 overexpression (p = 0.43). Using the Cox regression analysis, only the N factor (p = 0.0034) and M factor (p = 0.0325) were independent prognostic factors. Conclusions. Our results showed that in patients with ESCC, COX-2 overexpression was significantly correlated with fewer metastases and less advanced stage, but had no impact on survival. The status of local or distant lymph node metastasis was the most important prognostic factor. The biological role and pathophysiologic regulation of COX-2 overexpression in ESCC deserve further investigation.