Outcomes of neoadjuvant chemoradiotherapy in T4 rectal cancer patients: a real-world single institution experience.

Purpose: Treatment outcomes of locally advanced rectal cancer have improved significantly in recent decades. This retrospective study aimed to assess the efficacy of neoadjuvant chemoradiotherapy (nCRT) followed by surgery in patients with T4 rectal cancer and the different outcomes between T4a and T4b patients.

Materials and methods: A total of 60 clinically T4 rectal cancer patients who underwent nCRT were included in the analysis. Patient characteristics, treatment regimens, down-staging rates, pathological response, and overall survival (OS) were evaluated.

Results: Both T4a and T4b patients experienced down-staging following nCRT (36.6% and 6.2% respectively; p = 0.021). T4a patients exhibited a higher rate of pathological complete response (pCR) than T4b patients (13.3% in T4a vs. 0% in T4b; p = 0.122). After a median follow-up of 36 months, the OS and recurrence-free survival (RFS) of T4a patients were significantly higher compared to T4b patients (hazard ratio [HR] = 2.52, 95% confidence interval [CI] 1.05-6.05, p = 0.038 for OS; HR = 2.32, 95% CI 1.09-4.92, p = 0.025 for RFS).

Conclusion: This study provides valuable insights into the effectiveness of nCRT in T4 rectal cancer patients. Although down-staging was observed in both T4a and T4b subgroups, achieving a pCR remains a challenge, particularly in T4b patients. Further research is needed to optimize treatment strategies and enhance pCR rates in T4 rectal cancer patients to improve oncologic outcomes.