Impact of the IDEA Collaboration Study on Real-World Practice Patterns of Adjuvant Chemotherapy in Patients With Stage III Colon Cancer: A Population-Based Study

PURPOSE The International Duration Evaluation of Adjuvant Chemotherapy (IDEA) collaboration showed no significant clinical difference in outcomes in patients with stage III colon cancer (CC) treated with 3 versus 6 months of oxaliplatin-based adjuvant chemotherapy (O-ACT). We aimed to assess change in real-world practice patterns before and after publication of the IDEA study. METHODS This retrospective cohort study included patients age ≥18 years with stage III CC diagnosed between January 1, 2012, and December 31, 2020. Eligible patients received >1 dose of ACT between March 20, 2012, and May 10, 2021 inclusive. They were categorized into pre-IDEA (diagnosed before March 31, 2018) and post-IDEA (diagnosed on or after April 1, 2018) groups. The primary outcome was the median duration and type of ACT and factors associated with a shorter duration. Secondary outcomes were 2-year overall survival (OS) and cancer-specific survival (CSS). RESULTS In total, 740 patients were included (median age, 64 years, range, 27-90; 52.7% male). 48.8% had pT4 and/or pN2 disease. 77% received O-ACT. In the post-IDEA era, capecitabine plus oxaliplatin (CAPOX) ACT use increased (22.8%-50.7%, P < .001), and median duration of treatment was significantly shorter (2.7 v 4.8 months, P < .001). Factors associated with shorter O-ACT duration included diagnosis in the post-IDEA era (odds ratio, 2.08, P = .002), absence of pT4 and/or pN2 disease (hazard ratio HR, 1.71, P = .01), and receipt of CAPOX (HR, 2.58, P < .001). Two-year OS and CSS were comparable between pre- and post-IDEA eras (OS 95% v 94%; CSS 96% v 96%). CONCLUSION Our study shows that the results of the IDEA trial have been largely adopted in clinical practice with shorter duration of ACT in low-risk stage III CC.