Quantitative and qualitative characterization of plasma DNA identifies primary and recurrent colorectal cancer

Because plasma DNA may be a useful tool for cancer detection, we screened primary tumors and related multiple plasma samples at the time of surgery and during the follow-up period for plasma DNA level as well as for K-Ras mutations and p16(INK4a) promoter hypermethylation in colorectal cancer patients. At the time of surgery, DNA levels were higher in tumor patients than in healthy donors, and K-Ras and p16(INK4a) alterations were detected in 7 and I I cancers respectively, and in all related plasma samples. During the follow-up, plasma DNA levels decrease progressively but rapidly increased when a relapse occurred, whereas K-Ras and p16(INK4a) alterations were detected only in relapsed patients. Therefore, combined quantitative and qualitative analyses of plasma DNA confirm the presence of colorectal cancer, define disease-free status and indicate the presence of relapse. (C) 2008 Elsevier Ireland Ltd. All rights reserved.