Abstract: ObjectiveTo investigate the clinical value of detection of combined secreted frizzledrelated proteins 1 （SFRP1） and septin 9（SEPT9） gene methylation in stool DNA for early diagnosis of elderly colorectal cancer （CRC）. 
MethodsThirtyfive patients with CRC who were aged over 60 years from January 2016 to September 2016 were inrolled in the study. At the same time， 35 normal people， who passed the physical examination and were aged over 60 years， were selected as the control group. DNA in the stool of CRC and normal subjects was extracted. Methylation specific PCR （MSP） technique was used to detect the methylation status of SFRP1 and SEPT9 genes respectively. The difference of detection rate of single gene and double gene methylation in CRC patients was compared， and the detection rate of combined double gene methylation in CRC patients was compared with that in normal control group. The correlation between the methylation of SFRP1 or SEPT9 gene in CRC patients and the clinicopathological parameters， such as age， sex， and tumor location， was analyzed. 
ResultsThe detection rates of methylation of SFRP1 and SEPT9 genes in stool DNA of CRC patients were 45.71％ （16／35） and 51.43％ （18／35）， respectively， which were significantly higher than those in control group 857％ （3／35） and 14.29％ （5／35）， and the differences were statistically significant （P＜0.01）. There was at least one gene methylation in the stool DNA of 82.86％ （29／35） CRC patients， which was significantly higher than the single gene detection rate （P＜0.01）， which was also higher than that of the control group 17.14％ （6／35）， the difference was statistically significant （P＜0.01）. The methylation of SFRP1 or SEPT9 genes in CRC patients was not related to age， sex and tumor location （P＞0.05）. 
ConclusionThe methylation test of SFRP1 and SEPT9 genes in stool DNA is more sensitive than single gene detection， which is of great value in the early diagnosis of elderly colorectal cancer.

Key words: Elderly colorectal cancer, Stool DNA, Secreted frizzledrelated proteins 1 （SFRP1）, Septin 9（SEPT 9）, Methylation detection, Early diagnosis