The current standard of care for treatment of locally advanced rectal cancer consists of neoadjuvant whole pelvic RT with radiosensitizing single-agent 5-FU followed by surgery and adjuvant full dose chemotherapy (typically FOLFOX). For all clinical T3, T4, and/or lymph node positive rectal cancer patients the standard neoadjuvant radiation dose per fraction is 180 cGy delivered on consecutive weekdays over 5.5 weeks for a total of 5040 cGy. A potentially paradigm-changing approach is currently being investigated in a phase II/III trial in which neoadjuvant RT is omitting in favor of using full dose FOLFOX chemotherapy based on provocative data published from Memorial Sloan Kettering Cancer Center. We hypothesize that whole pelvic LDFRT using 40 cGy fractions for a total of 960 cGy can be safely added concurrently to neoadjuvant full dose FOLFOX as an alternative to standard neoadjuvant 5-FU chemoradiation. We further hypothesize that using LDFRT as a chemopotentiatior will significantly increase the pCR rate as reported by the Memorial Sloan Kettering pilot study of 27%. Lastly, due to the significantly lower radiation dose per fraction and lower total radiation dose we expect that this novel strategy will not cause higher rates of severe toxicity compared to neoadjuvant FOLFOX alone.