Use of Adjuvant Chemotherapy among Stage II Colon Cancer Patients in 10 Population-Based National Program of Cancer Registries.

Background: Some guidelines advise adjuvant chemotherapy be considered after surgical resection for high-risk stage II colon cancer patients; however, high-risk criteria are poorly defined and the long-term benefits are still debated. This study documents patterns of care by selected patient and tumor characteristics using a US population-based cohort of stage II colon cancer patients diagnosed in 2011. Methods: Data were collected from 10 specialized cancer registries participating in the Centers for Disease Control and Prevention's National Program of Cancer Registries' Enhancing Cancer Registry Data for Comparative Effectiveness Research project. The data were used to describe characteristics of stage II colon cancer patients treated by surgery to evaluate factors associated with receiving adjuvant chemotherapy. Results: Of the 3,891 stage II colon cancer patients, 14.3% were treated with surgery and adjuvant chemotherapy compared to 82.9% by surgery alone. The patients treated with adjuvant chemotherapy were predominately non-Hispanic white (66.1%), of younger age, and had private insurance (39.9%). Compared to surgery alone, the 5 characteristics associated with adjuvant therapy were younger age (adjusted odds ratio [AOR] for 5-year decrease below 75 years, 1.25; P < .001); more advanced stage (IIB/IIC vs IIA) (AOR, 4.79; P < .001); lymphovascular invasion (AOR, 1.76, P < .001); higher grade (III/IV vs I/II) (AOR, 1.84; P < .001); and registry area. Conclusions: In this population-based cohort, younger patients with more advanced stage II colon tumors, with lymphovascular invasion, and poor differentiation were more likely to receive adjuvant chemotherapy in addition to surgery. These characteristics align with high-risk profiles defined in guidelines. Ongoing data collection on outcomes, including recurrence and survival, will help clarify the benefits of adjuvant treatments for stage II colon patients.