Detection of epithelial messenger RNA in the plasma of breast cancer patients is associated with poor prognosis tumor characteristics

Purpose: Free plasma RNA has been scarcely studied in patients with cancer. Here we examine the presence of RNA from epithelial tumors in plasma from a series of breast cancer patients and its correlation with tumor character istics and circulating tumor cells. Experimental Design: beta -actin mRNA was analyzed to check the viability o f plasma RNA in samples from 45 patients with breast cancer and 25 controls . Nested primers were used to detect the presence of cytokeratin 19 (CK19) and Mammaglobin in the same samples. Eleven clinicopathological parameters were studied and correlated with molecular parameters. Additionally, we loo ked for circulating tumor cells in 16 of these patients and in 10 of the co ntrols. Results: All samples showed detectable quantities of beta -actin RNA. In co ntrols, 3 cases (12%) were positive for Mammaglobin, and 5 (20%) were posit ive for CK19 RNA; of the 45 patients, 27 cases (60%) were positive for Mamm aglobin, and 22 (49%) were positive for CK19. These differences were statis tically significant (P = 0.001). Tumor size (P = 0.01) and proliferative in dex (P = 0.02) were associated with the presence of Mammaglobin, CK19, or b oth RNAs in plasma. Pathological stage (P = 0.06) was close to significance . Although a statistical relationship was not demonstrated, 9 of the 10 pat ients with circulating tumor cells showed epithelial mRNAs in plasma. Conclusions: We conclude that epithelial tumor RNA is detectable in plasma from breast cancer patients and that this finding is associated with a prob able poor prognosis and circulating tumor cells.