Abstract
BACKGROUND: Adjuvant chemotherapy is currently offered routinely, as standard, after radical resection for patients with rectal cancer receiving neo-adjuvant chemoradiation. However, the efficacy of adjuvant chemotherapy in patients with ypTis-2N0M0 has not been documented to the same extent, and the survival benefit remained controversial. The purpose of this work was to determine the role of chemotherapy in patients with ypTis-2N0M0 classification. MATERIALS AND METHODS: Data were obtained from the Surveillance, Epidemiology, and End Results database (n = 4,217). A propensity score model was utilized to balance baseline covariates. RESULTS: Of the 4,217 included patients, 335 with ypTis-2N0M0 did not receive adjuvant chemotherapy. There were comparable cancer-specific survivals (CSS) between those undergoing adjuvant chemotherapy or not (log-rank test = 0.136, p = .712) in the overall sample. After propensity score matching, the cancer-specific survival did not differ between the chemotherapy and observation groups (log-rank test = 0.089, p = .765). Additionally, the Cox model did not demonstrate adjuvant chemotherapy as the prognostic factor, with hazard ratio = 0.95 (95% confidence interval 0.69-1.32) for CSS. Furthermore, the 10-year cumulative CSS was 78.7% and 79.4% between the chemotherapy and observation groups, indicating no significance, and no impact of adjuvant chemotherapy on survival was observed in different subgroups stratified by T stage, histological grade, histology, lymph nodes, and tumor size. CONCLUSION: Patients with ypTis-2N0 rectal cancer did not benefit from adjuvant chemotherapy after preoperative radiology and radical surgery in this cohort study. These results provided new insight into the routine use of adjuvant chemotherapy for patients with rectal cancer with completed neo-adjuvant radiotherapy and curative surgery. IMPLICATIONS FOR PRACTICE: Inconsistent recommendations for patients with rectal cancer receiving neo-adjuvant chemoradiation are offered by clinical guidelines. Adjuvant chemotherapy had no cancer-specific survival benefit, not only in the whole cohort, but also in the propensity score-matched cohort. A Cox model also confirmed adjuvant chemotherapy was not a significant prognostic factor in ypTis-2N0 rectal cancer. No survival benefit conferred by adjuvant chemotherapy was observed, regardless of whether T stage, histological type, grade, lymph nodes and tumor size varied.