Background: There is no conclusion about the most important contributor to the upswing of locally advanced colorectal cancer (LACRC) survival.
Methods: Data from the Surveillance, Epidemiology, and End Results (SEER) database was extracted to identify colorectal adenocarcinoma cancer patients at stage II and III diagnosed in the two periods 1989-1990 and 2009-2010. The statistical methods included Pearson's chi-squared test, log-rank test, Cox regression model and propensity score matching.
Results: The Cox regression model showed that hazard ratio (HR) of non-surgery dropped from 11.529 to 3.469 in right colon cancer (RCC), 5.214 to 2.652 in left colon cancer (LCC) and 3.275 to 3.269 in rectal cancer (RC) from 1989-1990 to 2009-2010. The 95% confidence intervals (CIs) for surgical resection in 2009-2010 were narrower than those in 1989-1990. HR became greater in LACRC without chemotherapy (from 1.337 to 1.779 in RCC, 1.269 to 2.017 in LCC, 1.317 to 1.811 in RC). There was no overlapping about the 95% CI of chemotherapy between the two groups. The progress of surgery was not linked to the improvement of overall survival (OS) of RCC (p = 0.303) and RC (p = 0.660). Chemotherapy had a significant association with OS of all colorectal cancer (CRC) patients (p = 0.017 in RCC; p = 0.006 in LCC; p = 0.001 in RC).
Conclusions: Advancements in chemotherapy regimen were the main contributor to the upswing of CRC survival. The improvements in surgery had a limited effect on improvements in CRC survival.