Does Doublet Chemotherapy Improve Survival in Rectal Cancer?

TOPLINE Total neoadjuvant therapy (TNT) integrating long-course radiotherapy with uninterrupted doublet chemotherapy improves disease-free survival by more than 8% compared with conventional neoadjuvant chemoradiotherapy (nCRT) in patients with high-risk locally advanced rectal cancer. The TNT approach also more than doubles the pathologic complete response rate and enhances metastasis-free survival while maintaining manageable toxicity. METHODOLOGY - High-risk locally advanced rectal cancer is associated with lower rates of major pathologic response and reduced tumor regression after conventional nCRT and neoadjuvant chemotherapy, underscoring the need for intensive strategies targeting both the primary tumor and micrometastatic disease in this population. A previous phase 2 study by the authors of this study researchers demonstrated that long-course radiotherapy combined with uninterrupted capecitabine plus oxaliplatin (CAPOX) achieved a promising complete response rate of 36.2% in high-risk patients, providing the foundation for this phase 3 trial. - Researchers conducted a multicenter, randomized, phase 3 trial at nine Chinese institutions between June 6, 2017, and December 27, 2023, enrolling 458 patients with stage II/III locally advanced rectal cancer and at least one high-risk feature (cT4a-b, cN2, mesorectal fascia involvement, or cT3c-d with extramural vascular invasion). - Patients were randomly assigned 1:1 to receive one of two treatment regimens. One group (n = 232) received total neoadjuvant therapy utilizing long-course radiotherapy combined with uninterrupted doublet chemotherapy (doublet-LC TNT). Specifically, this consisted of one cycle of induction capecitabine plus oxaliplatin (CAPOX; oxaliplatin 130 mg/m2 once every 3 weeks, capecitabine 1000 mg/m2 twice daily on days 1-14), followed by long-course radiotherapy with capecitabine 825 mg/m2 twice daily and oxaliplatin 130 mg/m2 once every 3 weeks for two cycles, then three cycles of consolidation CAPOX, before surgery. - The control group (n = 226) received nCRT consisting of long-course radiotherapy with concurrent capecitabine 825 mg/m2 twice daily, followed by surgery and six cycles of adjuvant CAPOX initiated 4-8 weeks postoperatively. Radiotherapy was delivered using intensity-modulated radiotherapy or volumetric modulated arc therapy to 50-50.4 Gy in 25-28 fractions in both groups, with median follow-up of 51 months. - The primary endpoint was disease-free survival, defined as time from random assignment to first occurrence of locoregional failure, distant metastasis, new primary colorectal cancer, or death from any cause. TAKEAWAY - At a median follow-up of 51 months, doublet-LC TNT improved 3-year disease-free survival compared with nCRT (74.8% vs 66.0%; hazard ratio [HR], 0.674; P = .016). - The 3-year metastasis-free survival rate was higher with doublet-LC TNT than nCRT (77.7% vs 67.6%; HR, 0.655; P = .013), and pathologic complete response rates were more than doubled (26.37% vs 9.80%; P < .001). - Locoregional failure rates remained low and comparable between groups (6.03% vs 6.19%; P = .943), while the 3-year overall survival rate showed no significant difference (90.2% vs 87.5%; HR, 0.727; P = .167). - Grade ≥ 3 adverse events during neoadjuvant treatment were more frequent with doublet-LC TNT (27.59% vs 8.56%; P < .001), but severe toxicities across the entire treatment course (28.02% vs 24.32%; P = .371) and major postoperative complications (3.98% vs 2.94%; P = .567) were comparable. IN PRACTICE “Compared with conventional nCRT, doublet-LC TNT improved [disease-free survival, metastasis-free survival, and pathologic complete response] rates with manageable toxicity. These findings support this intensified, doublet-based regimen as a standard option within the modern TNT paradigm,” the authors of the study wrote. SOURCE This study was led by Xin Wang, PhD, Division of Abdominal Tumor Multimodality Treatment, Department of Radiation Oncology, State Key Laboratory of Biotherapy and Cancer Center, and Ziqiang Wang, MD, PhD, Colorectal Cancer Center, Department of General Surgery, both from West China Hospital, Sichuan University in Chengdu, China. It was published online on July 23 in Journal of Clinical Oncology. LIMITATIONS According to the authors, the study has several limitations. First, enrolled patients were younger than 70 years, limiting generalizability to older patients. Second, mismatch repair results were incomplete because, at study initiation, international guidelines did not yet routinely recommend mismatch repair testing to guide treatment selection. Third, long-term outcomes remain immature at the current analysis, with limited disease-free survival events, and require longer follow-up. Finally, conventional nCRT was used as the control arm and, given the long accrual period, at present reflects an earlier treatment paradigm than current practice. DISCLOSURES This study received support from the Sichuan Science and Technology Support Project (No. 2024YFFK0338), the 1.3.5 project for disciplines of excellence at West China Hospital, Sichuan University (20HXJS003), and the 1.3.5 project for disciplines of excellence-Clinical Research Incubation Project at West China Hospital, Sichuan University (22HXFHO001). No potential conflicts of interest were reported by the authors. This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.