To compare the sensitivity and specificity estimates of Colvera with that of a commercially available CEA test for detection of recurrent disease in CRC subjects who are undergoing surveillance for recurrence.

This is an observational, prospective comparison study, where blood is collected for assay of methylated BCAT1 and IKZF1 DNA and CEA, from subjects who have undergone curative treatment for primary CRC of stages II and III (AJCC) and who are in remission and scheduled for follow-up radiological imaging as part of their surveillance program for recurrence. Participation is for one visit only as part of each subject's surveillance-monitoring schedule. Two K2-EDTA blood tubes and two PAXgene™ tubes will be collected Any evidence of methylated BCAT1 and/or IKZF1 DNA in blood represents a Colvera "positive" result. CEA levels of 5ug/L or higher will represent a "positive" result. Sensitivity and specificity of the Colvera and CEA test will be estimated and compared in a paired fashion in each case where recurrence status has been investigated and determined by the site clinical management team. Blood testing shall be performed and analyzed by qualified staff blinded to clinical status. This is a cross-sectional observational non-significant risk study, and test results will not be used for clinical management, i.e. there will be no interventions in subjects consenting to participate in this Research Study.

Inclusion Criteria:

1. Subject is 18 years or older, and capable and willing to provide informed consent.
2. Subject has undergone curative treatment for primary CRC of stages II and III (AJCC).
3. Subject has no clinical evidence of disease (NED) (after initial treatment)
4. Subject has concluded course of initial treatment for primary CRC (i.e. end of surgery, chemotherapy and/or radiotherapy)
5. Subject is willing/able to provide a blood sample

Exclusion Criteria:

1. Subject has evidence of residual disease.
2. Subject has other organ cancer at the time of recruitment.
3. Subject has prior history of recurrent CRC.
4. Subject has concurrent serious non-neoplastic illness that makes enrollment impractical or clinically inappropriate.
5. Subject is receiving chemo- or radiotherapy at the time of blood collection, or between blood collection and radiological imaging.

subjects who have undergone curative treatment for primary Colon or rectal cancer of stages II and III (AJCC), and who are in remission and scheduled for clinical follow-up (usually radiological imaging) as part of their surveillance program for recurrence.

The data collected by recruiting sites is captured without any PHI or identifiers in an Electronic Data Capture system managed for the sponsor by a CRO.