Purpose Reduction of adjuvant treatment duration may decrease toxicities without loss of efficacy in stage III colon cancer. This could offer clear advantages to patients and health care providers.

Methods In International Duration Evaluation of Adjuvant Chemotherapy (IDEA) France, as part of the IDEA international collaboration, patient with colon cancer patients were randomly assigned to 3 and 6 months of modified FOLFOX6 (mFOLFOX6: infusional fluorouracil, leucovorin, and oxaliplatin) or capecitabine plus oxaliplatin (CAPOX) by physician choice. The primary end point was disease-free survival (DFS), and analyses were descriptive.

Results A total of 2,010 eligible patients received either 3 or 6 months of chemotherapy (modified intention-to-treat population); 2,000 (99%) had stage III colon cancer (N1: 75%, N2: 25%); 1,809 (90%) received mFOLFOX6, and 201 (10%) received CAPOX. The median age was 64 years, and the median follow-up time was 4.3 years. Overall, 94% (3 months) and 78% (6 months) of patients completed treatment (fluoropyrimidines ± oxaliplatin). Maximal grade 2 and 3 neuropathy rates were 28% and 8% in the 3-month arm and 41% and 25% in the 6-month arm ( P < .001). Final rates of residual neuropathy greater than grade 1 were 3% in the 3-month arm and 7% in the 6-month arm ( P < .001). There were 578 DFS events: 314 and 264 in the 3- and 6-month arms, respectively. The 3-year DFS rates were 72% and 76% in the 3- and 6-month arms, respectively (hazard ratio [HR], 1.24; 95% CI, 1.05 to 1.46; P = .0112). In the 3 and 6-month arms, respectively, for patients who received mFOLFOX6, the 3-year DFS rates were 72% and 76% (HR, 1.27; 95% CI, 1.07 to 1.51); for the T4 and/or N2 population, they were 58% and 66% (HR, 1.44; 95% CI, 1.14 to 1.82); and for the T1-3N1 population, they were 81% and 83% (HR, 1.15; 95% CI, 0.89 to 1.49).

Conclusion IDEA France, in which 90% of patients received mFOLFOX6, shows superiority of 6 months of adjuvant chemotherapy compared with 3 months, especially in the T4 and/or N2 subgroups. These results should be considered alongside the international IDEA collaboration data.