Impact of Adjuvant Chemotherapy Following Neoadjuvant Concurrent Chemoradiotherapy and Total Mesorectal Excision in Rectal Cancer

Background/Aim: This study investigated the efficacy of adjuvant chemotherapy (ACT) after total mesorectal excision (TME) for rectal cancer in patients who responded well to neoadjuvant concurrent chemoradiotherapy (nCCRT). Patients and Methods: This retrospective study included patients with rectal cancer treated at Taipei Veterans General Hospital (2009-2017). Among 302 patients who underwent nCCRT and TME, 178 good responders [pathologic complete response (pCR), pT1, or pT2] were analyzed. Patients were grouped based on ACT administration. Primary outcomes included disease-free survival (DFS) and recurrence. Kaplan-Meier survival analysis and Cox proportional hazards regression were used to assess ACT efficacy. Results: The ACT group (n=96) had poorer baseline disease characteristics, including higher initial clinical T and N stages. However, recurrence rates did not differ significantly between ACT and non-ACT groups (23.2% vs. 17.7%, p=0.271). DFS curves showed no significant difference between ACT and non-ACT groups (p=0.360). Multivariable analysis confirmed that ACT was not significantly associated with DFS [adjusted hazard ratio (aHR)=0.76, 95% confidence interval (CI)=0.37-1.59]. However, the advanced surgical pT stage (pT3-pT4) was an independent predictor of recurrence (aHR=3.24, 95%CI=1.01-10.38, p=0.047). Conclusion: The role of ACT remains inconclusive after TME for rectal cancer in patients who respond well to nCCRT. Surgical pT stage, particularly pT3 and pT4, remain a significant predictor of recurrence, emphasizing its importance in risk stratification.