A Study of the Role of Circulating Tumor DNA in Predicting the Likelihood of Organ Preservation After Clinical Complete Response to Neoadjuvant Therapy for Rectal Cancer

In this research study, the investigator are performing blood draws to see if the presence or
absence of circulating tumor DNA (ctDNA), the genetic material in the participant's cancer's
cells, will help the investigators predict whether the participant's cancer will come back or
not.

Inclusion Criteria:

- Participants must have achieved a clinical complete response (cCR) within 3 months of
last therapy - defined as absence of residual ulceration, mass or mucosal irregularity
at endoscopic assessment - following neoadjuvant therapy with chemoradiation or
chemotherapy followed by radiation for stage I, II, or III non-metastatic rectal
cancer. (Whitening of the mucosa with presence of telangiectasia will be accepted as
cCR.)

- Participants must have original tumor tissue (formalin-fixed, paraffin-embedded
specimens) available for analysis

- Participants must be 18 years of age or older.

- Participants must be able to understand and willing to sign a written informed consent
document.

- Participants must have received long course chemoradiation to 40-54 Gy.

- Participants must have received at least 4 cycles of FOLFOX

- Participant must be no more than 3 months past the conclusion of initial
chemoradiation of rectal cancer (i.e., end of chemoradiation).

Exclusion Criteria:

- Participants may 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.