Pelvic Radiotherapy With Concurrent Neoadjuvant FOLFOX for Patients With Newly Diagnosed Rectal Adenocarcinoma

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. Specifically, this phase II trial intends to determine whether 6 cycles of neoadjuvant FOLFOX with concurrent LDFRT followed by comprehensive restaging and TME achieves favorable outcomes for patients with T3N0M0, T3N1M0, or T2N1M0 rectal cancer. As mentioned above, the current standard of care for all locally advanced rectal cancer patients includes radiosensitizing 5-FU and concurrent whole pelvic RT to 5040 Gy in 180 Gy once daily fractions. Per the proposed protocol, T3N0M0, T3N1M0, or T2N1M0 rectal cancer patients who are eligible to undergo a low anterior resection would receive whole pelvic RT to 960 cGy in 40 cGy fractions delivered twice daily on days 1-2 of each cycle of FOLFOX chemotherapy for a total of 6 cycles. Eligible study subjects include adults who are candidates for curative intent sphincter-sparing surgery and who lack high-risk features, particularly tumor encroaching upon the mesorectal fascia (within 3 mm) as determined by pre-treatment endoscopic ultrasound (EUS) and/or magnetic resonance imaging (MRI) or distal rectal tumors (\<5 cm from the anal verge).