To compare the sensitivity and specificity estimates of Colvera with that of a commercially available CEA test for detection of recurrent disease in subjects with colorectal cancer that have documented recurrence or no evidence of recurrence by CT.

The study will be carried out as a single cohort, observational, prospective study to compare sensitivity of Colvera to detect recurrent colorectal cancer confirmed by radiology imaging (CT) with CEA sensitivity in paired testing. 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 (No evidence of disease). Subjects will have recently (within 4 weeks of blood collection) had 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 PAXgene blood tubes (minimum 10 mL, maximum 20 mL) 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 was determined to be in remission at the conclusion of primary therapy and has been in clinical surveillance for at least 6 months. (No imaging is required for the determination of remission. Last treatment was at least 6 months earlier. No requirement to complete all of the initial adjuvant treatment plan.)
4. Subject has had a surveillance CT scan within the past 4 weeks and either has recurrent CRC or does not have recurrent CRC based on that CT scan result.
5. Subject is willing to provide a blood sample. (2 PAXgene tubes)
6. Definition of recurrence is evidence of local tumor recurrence or metastasis by CT scan of chest, abdomen and pelvis or other modalities that confirm recurrent CRC

Exclusion Criteria:

1. Subject has other cancer at the time of recruitment.
2. Subject has prior history of recurrent CRC.
3. Subject has a diagnosis of End Stage Renal Disease (ESRD), with or without current dialysis treatment.
4. Subject's life expectancy is less than one year based on performance status and clinical signs and symptoms.
5. Subject is receiving chemo- or radiotherapy at the time of blood collection, or between radiological imaging and blood collection.
6. Results of the recent surveillance CT of the chest, abdomen and pelvis are inconclusive regarding recurrence of CRC, and further work up (other imaging and/or biopsy) is not required at this time.

This prospective study will enroll 50 subjects with radiologic confirmation of recurrence of colorectal cancer and 50 subjects without CRC recurrence (documented by CT scan). Eligible study subjects will include men and women (18 years or older) of any race and ethnicity who have completed treatment (no further adjuvant chemotherapy or surgery currently planned) for primary CRC of stages II and III (AJCC, [2]), and have been considered by the site clinical management team for at least 6 months to be in remission. . (Concurrent imaging is not required as part of the clinical determination of remission. Subjects who have had a recent (within 4 weeks) or prior CT scan for purposes of surveillance are eligible.)

Data from each subject is captured without any identifiers in an electronic database.