Biomarkers in Patients With Rectal Cancer Undergoing Chemotherapy and Radiation Therapy

OBJECTIVES: Primary * Observe whether NF-kappa B is activated in response to treatment with external beam radiotherapy. * Correlate NF-kappa B pathway activation (presumed to be anti-apoptotic in nature) with therapeutic outcomes (as measured by rate of pathologic complete response or downstaging by endoscopic ultrasound \[EUS\]). Secondary * Study downstream events induced by NF-kappa B activation. * Determine global gene expression profiles at baseline and during chemoradiotherapy. * Correlate changes in gene expression (compared with the baseline gene expression pattern) induced by a single dose of external beam radiotherapy with patient outcomes (as measured by pathologic response rate or downstaging by EUS). * Study downstream events related to activation of p53 in response to treatment with radiotherapy. * Correlate p53 pathway-mediated events with clinical outcomes. OUTLINE: Patients receive fluorouracil or capecitabine and undergo radiotherapy and surgery per standard care. Patients undergo tumor pinch biopsies at baseline and on days 1 and 2 of chemoradiotherapy. At the time of final surgical resection, a portion of the remaining rectal tumor will be liquid nitrogen banked. Patients not deemed surgical candidates are evaluated by transrectal ultrasound 6-8 weeks after completion of chemoradiotherapy to assess ultrasound response (downstaging versus no downstaging). Tumor tissue samples are analyzed for NF-kappa B pathway activation; downstream events induced by NF-kappa B activation; changes in global gene expression; p53 function; apoptosis; and mRNA expression. Laboratory techniques used include tissue microarray, ELISA, RNase protection assay, fluorescence semi-quantitative PCR, TUNEL, IHC, and cDNA microarray analysis. If normal tissue from biopsies is not available, whole blood may be collected at any point while patient remains on study for correlative analysis or research related to rectal cancer.