Celecoxib in Treating Patients With Early-Stage Rectal Cancer

OBJECTIVES:

• Determine cyclooxygenase-2 (COX-2) over-expression in tumor specimens from patients with early-stage rectal cancer.
• Determine whether administration of a COX-2 inhibitor, celecoxib, results in changes in tumor (COX-2 overexpressing) levels of eicosanoids but not in levels in the surrounding normal tissue that is expected not to express COX-2.
• Determine whether surrogate markers of eicosanoid metabolism (i.e., serum VEGF levels, tumor prostaglandin E_2 [PGE_2], and the major urinary metabolite of PGE_2 [PGE-M]) in biological specimens from these patients correlate with changes noted in tumor tissue.
• Determine if there is a greater change in protein and gene expression from pretreatment biopsy levels in patient tumor specimens (COX-2 overexpressing) vs specimens of surrounding normal tissue (expected not to be COX-2 overexpressing).

OUTLINE: Patients receive oral celecoxib twice daily on days 1-5. Patients then undergo planned local excision or definitive radical resection on day 6.

Tumor tissue and normal tissue (at least 5 cm away from the tumor) samples are collected pretreatment. Post-treatment tissue samples are collected along with the surgery. Serum and urine samples are obtained at baseline and after administration of celecoxib. Tumor and normal tissue specimens are analyzed by assays measuring markers of cyclooxygenase-2 (COX-2) activity (i.e., COX-2 mRNA and protein, tumor prostaglandin E_2 [PGE_2], and VEGF). Tissue samples are also assessed by cDNA microarray and imaging mass spectrometry to determine overall changes in gene and protein expression from pretreatment levels. Surrogate markers of COX-2 activity in serum (i.e., VEGF) and urine (i.e., urinary metabolite of PGE_2 [PGE-M]) are also assessed and compared with changes noted in tumor tissue. COX-2 protein levels are determined by immunohistochemistry in patients with limited pretreatment tumor tissue specimens.