Postoperative Chemotherapy With or Without Bevacizumab for Patients With Stage II or III Rectal Cancer

Inclusion Criteria: * Histologically confirmed adenocarcinoma of the rectum meeting 1 of the following clinical (e.g., before neoadjuvant therapy) or pathologic staging criteria: * T3, N+, M0 * T3, N0, M0 * T4, N0, M0 * Any T, N1-2, M0 * T4, N0-2, M0 disease must meet 1 of the following criteria: * Clinically fixed tumor on rectal examination with tumor adherent to the pelvic sidewall or sacrum * Hydronephrosis on Computed Tomography (CT) scan or Intravenous Pyelogram (IVP) * Ureteric or bladder invasion as documented by cystoscopy and cytology or biopsy * Invasion into prostate * Vaginal or uterine involvement * Must have undergone complete tumor resection \>= 28 days ago and able to begin treatment by day 56 * Must have undergone concurrent neoadjuvant chemoradiotherapy\* * NOTE: \*Neoadjuvant chemoradiotherapy received on protocol NSABP-R-04 allowed provided it met these criteria * Must have undergone prior radiotherapy at 40-55.8 Gy\*\* AND received 1 of the following chemotherapy regimens: * Continuous infusion of fluorouracil with or without oxaliplatin; fluorouracil and leucovorin calcium * Capecitabine with or without oxaliplatin; capecitabine with or without oxaliplatin OR a continuous infusion of fluorouracil with or without oxaliplatin received on protocol NSABP-R-04 * NOTE: \*\*Intensity-modulated radiotherapy allowed * ECOG performance status 0-1 * Platelet count \>= 100,000/mm\^3 * Absolute granulocyte count \>= 1,500/mm\^3 * Bilir…