EP107 - Role of Induction or Consolidation Chemotherapy in T4b Rectal Cancer: The Real Benefit of Additional Chemotherapy

Purpose/Background: Colorectal cancer is the third most common malignancy. For locally advanced rectal cancer invading adjacent organs (cT4b), multimodality treatment as neoadjuvant chemoradiotherapy followed by multivisceral resection is required to achieve R0 resection and improve survival. Adding systemic chemotherapy as induction or consolidation strategy is gaining popularity in recent years, but most studies have excluded cT4b rectal cancer. We aimed to evaluate the benefit of adding induction or consolidation chemotherapy to chemoradiotherapy compared with conventional concurrent chemoradiotherapy before multivisceral resection.

Methods/Interventions: We conducted a single-center retrospective cohort study from January 2015 to December 2024. The data of patients diagnosed with cT4b rectal cancer planned for curative resection who received neoadjuvant therapy according to multidisciplinary team decisions were reviewed. Exclusion criteria were recurrent rectal cancer and distant metastasis at presentation. Patients were categorized as receiving induction or consolidation chemotherapy in addition to concurrent chemoradiotherapy (CCRT+CMT group) versus conventional chemoradiotherapy alone (CCRT group). To balance baseline characteristics, we performed 1:1 propensity score matching. Short-term outcomes were R0 resection rate, tumor regression grade (TRG), and postoperative complications. Long-term outcomes included 3-year overall survival, distant metastasis-free survival, and locoregional recurrence-free survival.

Results/Outcomes: A total of 102 patients were analyzed (CCRT+CMT, n=36; CCRT, n=66). Short-term outcomes were similar between groups: R0 resection 88.9% vs 89.4% (p=0.937); postoperative complications 47.2% vs 54.6% (p=0.479); TRG were not different (p=0.110). Propensity score matching (1:1) yielded 25 matched pairs after a median follow up of 2.8 years. The 3-year overall survival was higher in patients who received additional induction or consolidation chemotherapy combined with chemoradiotherapy group 100% [95% CI, -] vs 71.1% [95% CI, 46.1%-86.0%], p=.002. No significant between-group differences were observed in 3-year distant metastasis-free survival (78.3% in CCRT+CMT group vs 60.7% in CCRT group, p = 0.051) and 3-year locoregional recurrent-free survival (90.2% in CCRT+CMT group vs 75.8% in CCRT group, p = 0.129). Female (HR 4.5; 95% CI, 1.04-19.41; p = 0.04), ECOG status >1 (HR 21.9; 95% CI, 3.8-126.1; p = 0.001), and having intraoperative complication (HR 5.2; 95% CI, 1.5-17.6; p = 0.01) were observed to be associated with overall survival.

Conclusion/Discussion: Among patients with cT4b rectal cancer undergoing multivisceral resection, adding induction or consolidation chemotherapy to concurrent chemoradiotherapy significantly improved 3-year overall survival without increasing postoperative complications and showed a favorable trend in distant metastasis free survival. Induction or consolidation chemotherapy should be considered in the neoadjuvant strategy for cT4b rectal cancer.

Summary table
This table shows a brief summary of demographic characteristics, pretreatment tumor characteristics, treatment details, surgical details, and pathological results.


Survival outcome
This figure shows 3-year overall survival, distant metastasis-free survival, and locoregional recurrent-free survival.