Background: Although adjuvant chemotherapy is recommended for patients with stage II colon cancer characterized by poor prognostic features, its pros and cons remain a controversial issue. We aim to evaluate the real effectiveness of chemotherapy on stage II colon cancer as well as select suitable patients.
Methods: Patients during 1988-2013 were identified from the Surveillance, Epidemiology, and End Results (SEER) database. The competing risk regression model and propensity score matching method were used to evaluate colon-cancer-specific death (CCSD) and non-CCSD. Also, a competing-risk nomogram was constructed to identify risk of patients. Risk score (RS) was calculated according to nomogram.
Results: A total of 58,133 patients were included, 25.66% received chemotherapy, and 74.34% were without chemotherapy. In total, 19.95% and 25.78% of patients died of CCSD and non-CCSD, respectively. Univariate and multivariate analyses showed that receiving chemotherapy appears to be associated with more CCSD and less non-CCSD (HR 1.23, 95% CI 1.18-1.28; HR 0.45, 95% CI 0.43-0.47, respectively), even after adjustment for covariates and propensity score weighting. A competing-risk nomogram was established; the model was relatively good with a C-index of 0.661. Based on the RS, risk stage could only predict prognosis but failed to predict the benefit from chemotherapy.
Conclusions: The value of chemotherapy is much less than we thought. It is time to de-escalate chemotherapy for stage II colon cancer. CCSD, rather than overall survival, should be considered as an appropriate primary end point for future trials in stage II colon cancer.
Keywords: SEER; chemotherapy; colon cancer; competing; nomogram; survival.