This will be a prospective single arm biomarker (plasma-free DNA 5-hydroxymethylation) study. Fifty-five Adult patients with peritoneal metastases of colorectal and appendiceal origin who are candidates for a curative surgery and fulfill the inclusion criteria will be offered to participate in this study. In addition to the postoperative standard of care oncological surveillance of these patients which includes periodic physical examinations, cross sectional imaging studies (CT or MRI) and blood work for conventional tumor markers, serial measurements of plasma hydroxymethylation signatures will be performed. We will use a model developed in a separate pilot study to identify recurrent peritoneal metastasis based on 5hmC signatures. As part of this study, blood collection for measurements of plasma hydroxymethylation signatures of target genes will be performed at seven time points:
* Just before surgery (During the preoperative clinic visit or at the operating room).
* 5-7 days after surgery (just before hospital discharge).
* 6 weeks after surgery (first postoperative clinic visit).
* 3 months after surgery (second postoperative clinic visit).
* 6 months after surgery (third postoperative clinic visit).
* 9 months after surgery (fourth postoperative clinic visit).
* 12 months after surgery (fifth postoperative clinic visit). Standard of care surveillance elements that include patient history and physical examination, conventional blood biomarkers (CEA, CA 19-9 and CA 125) and cross sectional imaging of the chest, abdomen and pelvis will be undertaken simultaneously at similar time points. We will then compare the sensitivities of DNA hydroxymethylation signatures and conventional blood biomarkers in diagnosing clinically detectable recurrence at 1 year after surgery. We hypothesize that plasma hydroxymethylation signatures have higher sensitivity in identifying clinically detectable recurrence when compared with conventional tumor markers (CEA, CA 19-9 and CA 125).
