Prospective evaluation of methylated SEPT9 in plasma for detection of asymptomatic colorectal cancer

Abstract

Background: As screening methods for colorectal cancer (CRC) are limited by uptake and adherence, further options are sought. A blood test might increase both, but none has yet been tested in a screening setting.

Objective: We prospectively assessed the accuracy of circulating methylated SEPT9 DNA (mSEPT9) for detecting CRC in a screening population.

Design: Asymptomatic individuals ≥50 years old scheduled for screening colonoscopy at 32 US and German clinics voluntarily gave blood plasma samples before colon preparation. Using a commercially available assay, three independent blinded laboratories assayed plasma DNA of all CRC cases and a stratified random sample of other subjects in duplicate real time PCRs. The primary outcomes measures were standardised for overall sensitivity and specificity estimates.

Results: 7941 men (45%) and women (55%), mean age 60 years, enrolled. Results from 53 CRC cases and from 1457 subjects without CRC yielded a standardised sensitivity of 48.2% (95% CI 32.4% to 63.6%; crude rate 50.9%); for CRC stages I-IV, values were 35.0%, 63.0%, 46.0% and 77.4%, respectively. Specificity was 91.5% (95% CI 89.7% to 93.1%; crude rate 91.4%). Sensitivity for advanced adenomas was low (11.2%).

Conclusions: Our study using the blood based mSEPT9 test showed that CRC signal in blood can be detected in asymptomatic average risk individuals undergoing screening. However, the utility of the test for population screening for CRC will require improved sensitivity for detection of early cancers and advanced adenomas.

Clinical trial registration number: NCT00855348.

Keywords: Colonoscopy; Colorectal Adenomas; Colorectal Cancer Screening; Colorectal Neoplasm; Methylation.

Figure 1

Enhanced STAndards for the Reporting of Diagnostic accuracy studies (STARD) diagram of the disposition of subjects in the study, based on the template at http://www.stard-statement.org. ^aGerman law requires that data from subjects in Germany who withdrew cannot be retained or used for study purposes. ^bCR, colorectal. ^cSample either had too little volume or was unusable. ^dHGD, high grade dysplasia. ^eCases selected for laboratory analysis in a stratified random sampling.

Figure 2

PRospective Evaluation of SEPT (PRESEPT) results: target population and study subjects, age–sex distribution. Target sample and study sample distributions compared by sex and 5 year intervals of age at enrolment from 50 to 80 years (50–54, 55–59, etc). For the PRESEPT study sample (n=1516), the lowest interval of age (50, 55 years) includes one subject aged <50 years. Similarly, the highest interval (75, 80 years) includes 23 subjects who were aged 80 years or more. Proportions extending to the right in each plot represent proportions of the PRESEPT study sample overall; the sum of all proportions from both plots is 1. Proportions extending to the left in each plot represent proportions of the German and US population in the year 2000.

Figure 3

Methylated SEPT9 (mSEPT9) positivity rates by clinical findings. mSEPT9 assay positivity estimates and 95% CI by outcome category, standardised to the target population. Dot represents point estimate (Est), bars represent 95% CI. AA, advanced adenomas; CRC, colorectal cancer; HGD, high grade dysplasia; NA, non-advanced adenomas; NED, no evidence of disease; Test, raw result of assay; P, number of positive assays; Tot, number of valid measurements.

Figure 4

Methylated SEPT9 (mSEPT9) assay positivity estimates by age, sex and clinical findings. Comparing mSEPT9 assay positivity estimates and 95% CI by age group and outcome category and by sex and outcome category, standardised to the target population. Dot represents point estimate (Est), bars represent 95% CI. AA, advanced adenomas; CRC, colorectal cancer; HGD, high grade dysplasia; NA, non-advanced adenomas; NED, no evidence of disease; Test, raw results of assay; P, number of positive assays; Tot, number of valid measurements.