Celecoxib in Treating Patients With Early-Stage Rectal Cancer

RATIONALE: Studying samples of tissue, blood, and urine from patients with cancer in the laboratory may help doctors learn more about changes that may occur in DNA and identify biomarkers related to cancer. It may also help doctors predict how rectal cancer will respond to treatment with celecoxib. PURPOSE: This clinical trial is studying how well celecoxib works in treating patients with early-stage rectal cancer.