Clinical Analysis of the Efficacy and Safety of Different Neoadjuvant Strategies in the Treatment of Locally Advanced Rectal Cancer.

Objective: In this study, we retrospectively analysed the efficacy and safety of three treatment models, namely, short-course radiotherapy sequential XELOX chemotherapy, neoadjuvant mFOLFOX6 concurrent radiotherapy and long-course concurrent radiotherapy with total mesorectal excision (TME) after treatment of locally advanced rectal cancer with high-risk factors.

Methods: We collected clinical data on 177 patients with locally advanced rectal cancer (cT3-4 and/or cN+) who were treated at the Department of Abdominal Oncology of the Affiliated Cancer Hospital of Guizhou Medical University from December 2017 to December 2022. All patients were associated with 2-3 risk factors [T4b, N2, Extramural Vascular Invasion (EMVI), Mesorectal Fascia (MRF) positivity], positive lateral lymph nodes. Among them, there were 45 cases in the short course radiotherapy sequential XELOX chemotherapy group (RT + XELOX group); 64 cases in the neoadjuvant mFOLFOX6 concurrent radiotherapy group (mFOLFOX6 + CRT group); and 68 cases in the long course concurrent radiotherapy group (CRT group). The RT + XELOX group and mFOLFOX6 + CRT group completed radiotherapy and 4 cycles of neoadjuvant chemotherapy, respectively, and then rested for 1-2 weeks before TME surgery; the CRT group completed concurrent radiotherapy and then rested for 6-8 weeks before TME surgery.Adjuvant chemotherapy was conducted after surgery in each of the three groups: 2 cycles of adjuvant chemotherapy with XELOX regimen in the RT + XELOX group, 4-6 cycles of adjuvant chemotherapy with mFOLFOX6 in the mFOLFOX6 + CRT group, and 8-12 cycles of adjuvant chemotherapy with mFOLFOX6 in the CRT group.The pathological complete response rate (pCR rate), tumour downstage rate, tumour complete resection rate (R0 resection rate), local recurrence rate, distant metastasis rate, overall survival rate, incidence of adverse reactions, surgical complications and completion rate of perioperative systemic chemotherapy were compared among patients in the three groups of cases after TME.

Results: The pCR rate (21.95% vs 17.24% vs 5.00%, p = 0.034) and and tumour downstage rate (78.05% vs 68.97% vs 53.33%, p = 0.029) were higher in the RT + XELOX group and mFOLFOX6 + CRT group compared to the CRT group. The RT + XELOX group had a lower 3-year distant metastasis rate (14.63% vs 36.67%, p = 0.048) and improved 3-year overall survival (76.57% vs 48.56%, p < 0.001) compared to the CRT group. There was no significant reduction in the 3-year distant metastasis rate in the mFOLFOX6 + CRT group versus the CRT group (27.59% vs 36.67%, p = 0.719), and the 3-year overall survival was similar (51.23% vs 48.56%, p = 0.35). Multi-logistic regression analysis and stratified analysis showed that patients in the RT + XELOX group and mFOLFOX6 + CRT group were more likely to achieve pCR than the CRT group (RT + XELOX group: OR 7.3, 95% CI [2.6-20.8], p < 0.001; mFOLFOX6 + CRT group OR 2.9, 95% CI [1.1-7.9], p = 0.036). The completion rates of perioperative systemic chemotherapy in the RT + XELOX, mFOLFOX6 + CRT, and CRT groups were 82.93% vs. 84.48% vs. 61.67% (χ=9.95, p = 0.007), respectively. And there were significant differences in grade 3-4 leukopenia and thrombocytopenia (incidence of leukopenia: 15.50% vs. 7.81% vs. 1.47%, p = 0.045; incidence of thrombocytopenia: 13.33% vs 7.81% vs 1.47%, p = 0.027). There was no significant difference in the incidence of intraoperative and postoperative complications among the three groups (p > 0.05).

Conclusions: RT + XELOX group and mFOLFOX6 + CRT group significantly improved the near-term outcome (e.g., pCR rate) in patients with locally advanced rectal cancer with high-risk factors compared with CRT group. The RT + XELOX group also reduced the 3-year distant metastasis rate, increased the 3-year overall survival rate, and did not increase the incidence of perioperative surgical complications. It provides an effective means for the comprehensive treatment of locally advanced rectal cancer and has important clinical guidance and application value.