Predictive risk-score model for selection of patients with high-risk stage II colon cancer for adjuvant systemic therapy.

ABSTRACT

BACKGROUND: Adjuvant systemic therapy is selectively considered for high-risk stage II colon cancer, but which patients benefit most from adjuvant systemic therapy is unclear. METHODS: Patients who underwent resection of stage II colon cancer were identified from the National Cancer Database (2010-2016). Risk-factors for decreased overall survival on multivariable analysis were used to establish a predictive risk-score model for all-cause mortality. After propensity matching within each risk group, 5-year overall survival was estimated based on receipt of adjuvant systemic therapy. RESULTS: Of the 15,241 patients evaluated, 2,857 (18.8%) received adjuvant systemic therapy. Risk factors for decreased overall survival included age >75 (hazard ratio 3.3, P < .001), male sex (hazard ratio 1.2, P < .001), White/Black race (hazard ratio 1.4, P = .020), preoperative carcinoembryonic antigen >3.5 ng/mL (hazard ratio 1.6, P < .001), T4a T-stage (hazard ratio 2.0, P < .001), T4b T-stage (hazard ratio 2.4, P < .001), lymphovascular invasion (hazard ratio 1.2, P = .003), perineural invasion (hazard ratio 1.3, P = .003), and non-R0 proximal/distal resection margins (hazard ratio 1.7, P < .001). An internally validated risk-score model using these factors was developed composed of low-risk (n = 8,489), moderate-risk (n = 4,623), and high-risk (n = 2,129) groups; within each group, 19.9%, 15.7%, and 20.8% of patients, respectively, received adjuvant systemic therapy. After propensity matching, adjuvant systemic therapy was not associated with improved 5-year overall survival for low-risk patients (89.8% vs 88.3%, P = .280), but was for moderate-risk (80.5% vs 70.8%, P < .001), and high-risk (65.2% vs 45.7%, P < .001) patients. CONCLUSION: A predictive risk-score model incorporating patient and tumor factors identifies a high-risk cohort of stage II colon cancer patients who may benefit from adjuvant systemic therapy, although the minority of these patients appear to be receiving treatment.