Cell-free DNA is extracellular nucleic acids found in cell-free plasma/serum of humans. Circulating extracellular DNA can be found in healthy persons, persons with nonmalignant diseases, as well as persons with various malignancies. Given the recent approval of a liquid biopsy, the use of circulating tumor DNA as a novel and non-invasive test for the diagnosis and surveillance of cancer is a rapidly growing area of interest.
This study was carried out in Menoufia University hospital in the period from May 2015 to December 2015. It was conducted on 80 individuals classified into: Group I: included 40 colorectal cancer (CRC) patients Group II: included 20 patients with colorectal benign diseases. Group III: included 20 healthy controls. Laboratory investigations including detection of quantitative analysis of circulating cell free DNA (ccf-DNA) through detection of short (115bp) DNA fragments in serum by real time quantitative PCR by amplifying the ALU repeats (ALU-qPCR) and CA19 9 serum level by ELISA.
There was significant statistical difference in serum level of ALU 115 between group I (1123.8±356.3) and both of group II (432.2±147.8) and III (317±105) both (p = 0.001), where there was non-significant statistical difference in serum levels ALU 115 between group II & III (p = 0.180). There was significant statistical difference in serum level of CA19-9 between group I (42.4±92.3) and both of group II (10.5±5.87) (p = 0.032) and III (9.74±5.62) (p = 0.013), where there was non-significant statistical difference in serum levels of CA19-9 between group II & III (p = 0.684). The diagnostic accuracy for distinguishing primary CRC patients from normal control by ALU 115 is (85%), with sensitivity (83%), specificity (90%), positive predictive value (96%) and negative predictive value (64%) at cut off point of 426 ng/ml. The diagnostic accuracy by CA19-9 is (59%), with sensitivity (60%), specificity (55%), positive predictive value (80%) and negative predictive value (31%) at cut off point of 8.45 U/ml. combined detection of ALU115 and CA19-9 improved the sensitivity to (88%). There was a significant positive correlation between ALU 115 serum level and tumor grade (p = 0.024), also between CA19-9 and primary tumor stage and presence of metastases (p = 0.012) and (p = 0.044).
It was concluded that serum DNA concentrations may be valuable in early diagnosis and monitoring of colorectal cancer patients.
Clinical trial identification
Legal entity responsible for the study
All authors have declared no conflicts of interest.