Adjuvant chemotherapy does not improve cancer-specific survival for pathologic stage II/III rectal adenocarcinoma after neoadjuvant chemoradiotherapy and surgery: evidence based on long-term survival analysis from SEER data.

PURPOSE: Adjuvant chemotherapy is controversial in rectal cancer, especially after neoadjuvant chemoradiotherapy (NCRT). This retrospective study aims at evaluating adjuvant chemotherapy's long-term survival benefits in stage II and stage III rectal adenocarcinoma (RC). METHODS: This study obtained data from the Surveillance, Epidemiology, and End Results (SEER) database registered between 2010 and 2015. The survival analyses used the Kaplan-Meier method and were compared by log-rank test. The factors that affect survival outcomes were analyzed by univariate and multivariate Cox regression. The propensity score matching (1:4) was used to ensure the balance of variables between different groups. RESULTS: The median follow-up time for overall patients was 64 months. The 5-year overall survival (OS) and cancer-specific survival (CSS) rates were 51.3% and 67.4% in the adjuvant chemotherapy (-) group and 73.9% and 79.6% in the adjuvant chemotherapy ( +) group (p < 0.001, p = 0.002). However, subgroup analysis showed adjuvant chemotherapy after NCRT improved the 5-year OS but not CSS rates in stage II and stage III RC (p = 0.003, p = 0.004; p = 0.29, p = 0.3). Univariate and multivariate analyses found adjuvant chemotherapy after NCRT was an independent prognosis factor of OS but not CSS (HR 0.8, 95%CI 0.7-0.92, p < 0.001; p = 0.276). CONCLUSION: The survival benefits from adjuvant chemotherapy were associated with the status of NCRT for pathological stage II and III RC. For patients who did not receive NCRT, adjuvant chemotherapy is needed to significantly improve long-term survival rates. However, adjuvant chemotherapy after NCRT did not significantly improve long-term CSS.

The benefit of adjuvant chemotherapy in pathological T1-3N0M0 rectal mucinous adenocarcinoma: no improvement survival outcomes based on long-term survival analysis of large population data.

Background: Currently, the benefits of the administration of adjuvant chemotherapy (AT) in pathological low-risk rectal mucinous adenocarcinoma (RM) with T1-3N0M0 are unclear. The objective of this study is to retrospectively investigate the clinical significance of AT in terms of survival outcomes for patients with pathological T1-3N0M0 RM using data from a large population. Methods: The patient data were collected from the Surveillance, Epidemiology, and End Results (SEER) Program. The Chi-squared test was used to analyze categorical variables. The survival curves were compared using the log-rank test and the Kaplan-Meier method. A multivariate proportional hazards regression (Cox) model was applied to identify the independent prognostic factors of survival outcomes. Propensity score matching (PSM) was utilized to eliminate the differences between groups and estimate AT's effect. Results: The median follow-up duration for the rectal cancer (RC) cohort was 116 months. Multivariate analyses revealed that RM was a significant adverse prognostic factor, correlating with poorer overall survival (OS) and cancer-specific survival (CSS) for RC [hazard ratio (HR): 1.226, 95% confidence interval (CI): 1.094-1.375, P<0.001; HR: 1.446, 95% CI: 1.242-1.683, P<0.001]. Among patients with RM, the rates of 5-year OS and CSS were 68.6% and 79.3% in the AT (-) group, respectively. Additionally, the AT (+) group exhibited similar rates of 65.6% for 5-year OS and 74% for CSS (P=0.80, P=0.26). Subtype analysis according to preoperative therapy status showed that AT also did not significantly affect survival outcomes (P=0.65, P=0.34; P=0.90, P=0.76). Conclusions: Our study found that RM is a poor prognostic factor in pathological T1-3N0M0 RC. However, AT does not appear necessary to improve survival outcomes of pathological T1-3N0M0 RM.