RESUMO
BACKGROUND: Colorectal cancer (CRC) is a significant malignancy with widespread implications. Despite progress in surgical interventions for rectal cancer, improvements in overall prognosis remain disproportionate. Standard preoperative chemoradiation, while established as the standard treatment for the majority of rectal cancers, exhibits limited effectiveness in enhancing disease-free survival (DFS) and mitigating distant metastases, particularly in cases of locally advanced rectal cancer (LARC). METHODS: This randomised clinical trial assessed 286 patients with LARC in two paralleled groups. Group A underwent six courses of neoadjuvant MFOLFOX chemotherapy, chemoradiation, surgery, and six adjuvant chemotherapy cycles. Group B received concurrent chemoradiation, surgery, and twelve adjuvant chemotherapy cycles. Patient evaluations were achieved at multiple stages of treatment and follow-up. RESULTS: Group A had significantly lower local recurrence (11.64%) than Group B (21.74%, P = 0.025). The distant metastasis rate in Group A (8.90%) was lower than in Group B (20.29%) but was not significant (p = 0.143). More patients in Group A experienced downstaging (80.82% vs. 60.87%, p < 0.001). Specifically, 72.60% demonstrated downstaging of tumour invasion and 54.79% downstaging of lymph node involvement, compared to 57.25% and 41.30% in Group B (p = 0.009 and p = 0.025, respectively) as well as higher pCR rate (26.03% vs. 15.25%, p = 0.030) and three-year DFS rate (82.19% vs. 71.01%, p = 0.035) in group A compare to group B. CONCLUSION: This innovative strategy for LARC showed promising results with lower local recurrence and higher rates of downstaging and pCR. Treatment side effects were similar in both groups but less frequent in Group A. Anaemia was the most common haematological side effect (A: 58%, B: 68%), and peripheral sensory neuropathy was the most common non-haematological complication (A: 63%, B: 64%). These findings suggest this regimen could be a valuable therapeutic approach for LARC. TRIAL REGISTRATION: This trial was registered on 2023-12-08 within the IRCT.IR database under the number IRCT20210308050628N1.