S0713: Oxaliplatin, Capecitabine, Cetuximab, and RT Followed By Surgery in Pts W/Stage II or III Rectal Cancer

OBJECTIVES: * To assess the pathologic complete response rate for the combination of oxaliplatin, capecitabine, and cetuximab alone and concurrently with external beam radiotherapy for patients with adenocarcinoma of the rectum, stages II and III with wild-type K-ras. * To estimate the 3-year disease-free survival probability in this patient population when treated with this regimen. * To assess the frequency and severity of toxicities associated with this regimen in these patients. * To explore, preliminarily, the association between expression levels of genes involved in the DNA repair, EGFR (epidermal growth factor receptor), angiogenesis, and 5-FU pathway (i.e., k-ras, TS \[Thymidylate Synthase\], ERCC-1 \[excision repair cross complementing-1), TP \[Thymidine phosphorylase\], DPD \[Dihydropyrimidine dehydrogenase\], EGFR, VEGF \[vascular endothelial growth factor\], and IL-8 \[interleukin-8\]) and pathologic complete response. (Due to advances in methodology, the translational medicine objectives are being reconsidered. Therefore, results for this objective are not reported) * To explore, preliminarily, the intratumoral gene expression levels of these genes after completion of study treatment.(Due to advances in methodology, the translational medicine objectives are being reconsidered. Therefore, results for this objective are not reported) * To obtain, preliminarily, data on genomic polymorphisms of these genes for correlation with clinical outcome and toxicity. (Due to advances in methodology, the translational medicine objectives are being reconsidered. Therefore, results for this objective are not reported) OUTLINE: This is a multicenter study. * Neoadjuvant therapy (course 1): Patients receive oxaliplatin IV over 2 hours once a week for 5 weeks, oral capecitabine twice daily 5 days a week for 5 weeks, and cetuximab IV over 1-2 hours once a week for 5 weeks. * Neoadjuvant therapy with concurrent radiotherapy (course 2): Beginning two weeks later, patients receive oxaliplatin IV over 2 hours once a week in weeks 1, 2, 4, and 5. Patients also receive capecitabine and cetuximab as in course 1. Patients also undergo external beam radiotherapy 5 days a week for 5 weeks beginning in week 1. Treatment continues in the absence of disease progression or unacceptable toxicity. Patients undergo surgery 3-8 weeks after completion of chemoradiotherapy. Blood samples are collected for germline polymorphism testing and tissue samples are collected and assessed for gene expression analysis. After completion of study treatment, patients are followed every 6 months for 4 years.