Published online Jul 7, 2022. doi: 10.3748/wjg.v28.i25.2920
Peer-review started: January 16, 2022
First decision: March 8, 2022
Revised: March 18, 2022
Accepted: May 27, 2022
Article in press: May 27, 2022
Published online: July 7, 2022
Colorectal cancer (CRC) is currently a health problem of global concern. In recent years, the incidence of CRC presents a trend of gradual increase. Most patients have unobvious early symptoms, and they are commonly in mid and advanced stages when the symptoms become evident, with rather high mortalities. Featuring high throughput, fastness, and rich information, next generation sequencing (NGS) can greatly shorten the detection time, which is a research hotspot at home and abroad at present.
As we all know, histopathological examination is the gold standard of diagnosis, but its invasiveness limits its development. Therefore, it is imperative to explore the screening, diagnosis, and prognosis of CRC by strong specificity, high sensitivity, and non-invasive methods.
In this study, NGS technology was used to conduct genetic testing on stool samples of CRC patients, and the results were compared with the corresponding tumor tissue genetic testing results. The aim was to find genes or gene combinations with high specificity and sensitivity in the stool and establish a technical platform for CRC screening and diagnosis and curative effect monitoring through fecal DNA detection, providing a strong basis and support for personalized diagnosis and treatment of CRC.
NGS was used to sequence the DNA in stools of patients with CRC, which were then compared with the genetic testing results of the stool samples of normal control and benign intestinal disease groups, as well as the tumor tissues of CRC patients. Specific genes or gene combinations in fecal DNA suitable for diagnosis and prognostic prediction of CRC were screened, and their significance in diagnosing CRC and predicting patients' prognosis was comprehensively evaluated.
High mutation frequencies of TP53, APC, and KRAS were detected in the stools and tumor tissues of CRC patients prior to surgery. Contrastively, no pathogenic mutations of the above three genes were noted in the postoperative stools, or two control groups. This indicates that the tumor-specific DNA was detectable in the preoperative stools of CRC patients. Compared to the postoperative stools and the stools in the two control groups, the pathogenic mutation frequencies of TP53 and KRAS were significantly higher for the preoperative stools (P < 0.05), suggesting that fecal TP53 and KRAS genes can be used for CRC screening, diagnosis, and prognostic prediction. No significant difference in the pathogenic mutation frequency of the APC gene was found from the postoperative stools or the two control groups (P > 0.05), so further analysis with larger sample size is required. In 27 preoperative stools of CRC patients, the sensitivity and negative predictive value of TP53- KRAS gene combination detection were higher than those of TP53 mutation or KRAS mutation alone, suggesting that TP53-KRAS gene combination detection can improve the detection rate of CRC. The "undetected" mutation sites found in preoperative stools and tumor tissues may be new mutation types in the occurrence and development of CRC, which need to be further studied. In addition, some mutations of "unknown clinical significance" were found, and their clinical value is worth further study.
NGS-based fecal genetic testing can be used as a complementary technique for the CRC diagnosis. Fecal TP53 and KRAS can be used as specific genes for the screening, diagnosis, prognostic prediction, and recurrence monitoring of CRC. Moreover, the combined testing of TP53 and KRAS genes can improve the CRC detection rate.
Fecal genetic detection is a new method for CRC diagnosis, which has the advantages of non-invasiveness, convenient sampling, and dynamic monitoring. Although the sensitivity of fecal genetic test in CRC screening is low, it is certain that it has great potential and broad prospects in the diagnosis and prognosis assessment of CRC. In addition, the "undetected" mutation sites in preoperative stools of CRC patients and the "unknown clinical significance" mutation sites are related to the occurrence and development of CRC, which requires further research and exploration.