Quantification of total plasma cell-free DNA in ovarian cancer using real-time PCR

Our objective was to compare the levels of total circulating plasma cell-free DNA (CfDNA) using real-time PCR in patients with late-stage ovarian cancer with those in unaffected controls. Following IRB consent, DNA was extracted from archived frozen plasma of 19 patients with primary ovarian carcinoma and 12 age-matched controls using Qiagen DNA Isolation Kits. Quantification of total CfDNA was performed using real-time PCR with the TaqMan Assay for GAPDH, beta-actin and beta-globin and the number of genome equivalents (GE/mL) were determined from a standard curve. CfDNA levels of these loci were compared between the groups with Student's t-test, with P < 0.05 being statistically significant. The mean age of the patients was 61.6 years (+/-9.6) and of the controls was 54 years (+/-12.2). All patients had high-grade, advanced stage (III or IV) serous ovarian carcinomas. Preoperative CA-125 levels ranged from 43 to 15,626 IU/mL (mean 2487.2 +/- 3686 IU/mL). Total CfDNA in ovarian cancer was higher among patients with ovarian cancer as compared to controls at all three loci: GAPDH (P = 0.022), beta-actin (P = 0.025), and beta-globin (P = 0.0089). CfDNA is elevated in advanced stage disease compared to controls. These preliminary results suggest that total CfDNA in the plasma of patients with ovarian cancer may be useful for noninvasive screening and disease surveillance.