This pilot study is being done to answer the following question: Will patients with margin-clear Stage 2 or 3 rectal cancer who don't require a colostomy agree to be randomized to 'surgery only' or 'chemotherapy and then surgery'? Study participants will be randomized to receive either 12 weeks of chemotherapy before rectal cancer surgery or they will proceed directly to surgery. The researchers hypothesize that patients with margin-clear clinical Stage II or III rectal cancer can avoid neo-adjuvant (i.e., pre-operative) radiation and chemotherapy treatments and go directly to surgery. A positive pilot study will support funding requests for a related large efficacy trial; this larger trial, if positive, should lead to an important de-escalation innovation - avoiding use of neo-adjuvant chemoradiation and associated toxicity risks for patients with margin-clear Stage II or III rectal cancer.