ctDNA and Organ Preservation/Pathologic CR in Rectal Cancer

This prospective observational, non-therapeutic study for patients with T3, T4, or node positive rectal cancer eligible to undergo total neoadjuvant therapy. This research study involves the collection of data and biospecimens (blood and tissue) to see if the presence of circulating tumor DNA (genetic material) ctDNA will help monitor rectal cancer more closely and potentially detect a recurrence before routine scans, performed per standard of care C2i Genomics, a biotechnology company, and the Spier Foundation are supporting this research study by providing funding for the study.

The research study procedures include screening for eligibility and the collection of data and biospecimens. Non-operative management is offered as part of routine clinical care. It is expected that up to 60 participants will be enrolled, with the goal that 55 participants will take part in this research study . Participants enrolled on the study will remain on study for up to 60 months.

Inclusion Criteria: * Participants with T3, T4, or node-positive non-metastatic rectal cancer. * Participants must have original tumor tissue (formalin-fixed, paraffin embedded specimens) available for analysis or be willing to undergo a baseline research biopsy. * Participants must be 18 years of age or older. * ECOG 0-2. * Participants must be eligible for at least 3 months of FOLFOX, FOLFIRINOX/FOLFOXIRI, or CAPOX * Participants must be eligible for long course chemoradiation to 40-54 Gy. * Participants must be able to understand and willing to sign a written informed consent document. Exclusion Criteria: * Participants must not have any other organ cancer evident at the time of enrollment. * Participants may not have any other concurrent serious illness that makes participation on this study impractical or clinically inappropriate. * Participants must not be actively or planning to be pregnant or breastfeeding