Impact of complete pathological response outcome in Latin American patients with rectal cancer.

Abstract

58 Background: Rectal cancer is one of the leading cancer-related causes of death worldwide. Nevertheless, complete pathological response (pCR) to neoadjuvant treatment has been associated with a decrease in local recurrence and distant disease, and therefore an improvement in disease-free survival (DFS) and overall survival (OS). The aim of this study was to evaluate the impact of pCR in DFS and OS Mexican patients with rectal cancer. Methods: Retrospective, observational study. Included patients with rectal adenocarcinoma treated with neoadjuvant chemo-radiotherapy between 1998 and 2021. Statistical analysis: X2 and t-test, Kaplan Meier, Log Rank, and Cox Regression. Statistical significance p <0.05 bilaterally. Results: A total of 707 patients were included in the analysis. 52.3% were male with a median age of 57 (18 – 86) years. According to clinicopathological features, moderate-grade was the most prevalent at 66%, 38.5% were low-rectum and 32% of patients reported an ACE<10mg/dL. Patients were divided into 2 groups: pCR (n=155) and non-pCR (n=552) for the analysis. According to surgical margins, 89%(n=491) non-pCR-patients reported R0 (p=0.003). Recurrence rate was 12.9%(n=20) versus 35.7%(n=197) in pCR and non-pCR respectively (p<0.001). Regarding DFS analysis, pCR-patients median-DFS was Not Reached (NR), while non-pCR-patients median-DFS was 154 months (p<0.001; HR:0.32, 95%CI:0.20-0.51). At OS analysis, pCR-patients median-OS was NR, non-pCR-patients median-OS was 166 months (p<0.001; HR:0.41,95%CI 0.26-0.65). At DFS-multivariate analysis, location (p<0.001; HR:1.47, 95%CI:1.20-1.80) and rPC (p=0.013; HR:0.48,95%CI:0.27-0.85) remained predictive factors of DFS. At OS-multivariate analysis, ACE (p=0.047; HR:1.37, 95%CI:1.00-1.89) and pCR (p=0.009; HR:0.45, 95%CI:0.24-0.81) remained as predictive factors of OS. Conclusions: The pCR rate in our population is similar of what is reported in the literature. Our study demonstrates that pCR significantly impacts DFS and OS, rectal cancer patients. Total neoadjuvant chemo-radiotherapy, short-scheme-radiotherapy, and immunotherapy in selected populations can achieve doubling the percentage of pCR. [Table: see text]