Impact of cyclooxygenase-2 and prostaglandin-E2 expression on clinical outcome after pulmonary metastasectomy

Background: Pulmonary metastasectomy (PM) is a standard procedure in the treatment of stage IV colorectal cancer (CRC). In most centers the indication for PM is solely based on clinical factors without taking the tumor biology into account. This results in diverse outcomes ranging from long-term remission to early recurrence. Inflammation is considered a hallmark of cancer development and progression. On the other hand the accessibility of CRC cells to the immune system reflects the grade of tumor aggressiveness. We sought to investigate the impact of cyclooxygenase-2 (COX-2) and prostaglandin-E2 (PGE2) expression in pulmonary metastases on different outcome parameters following PM. Methods: From 04/2009 to 11/2013 53 patients with complete PM for CRC were included in this single-center study. Tissue samples of resected pulmonary metastases and available corresponding primaries were collected and assessed by immunohistochemistry for COX-2 and PGE2 expression of the tumor tissue and the peritumoral stroma. Results were correlated with clinical outcome parameters. Results: COX-2 and PGE2 were detected in nearly every pulmonary CRC metastasis. Staining intensities of pulmonary metastases correlated only weakly with intensities found in primary tumors. When dividing metastases in high expressing and low expressing tumors, a trend towards longer recurrence free survival and improved survival was found in tumors with strong COX-2 and PGE2 staining. Conclusions: In conclusion, this pilot study shows that COX-2 and PGE2 are uniformly overexpressed in pulmonary metastases from CRC. High expression of COX-2 and PGE2 seems to reflect a beneficial tumor biology with late tumor recurrence and prolonged overall survival after PM.