Duration of Adjuvant Chemotherapy for Stage III Colon Cancer

Abstract

Background: Since 2004, a regimen of 6 months of treatment with oxaliplatin plus a fluoropyrimidine has been standard adjuvant therapy in patients with stage III colon cancer. However, since oxaliplatin is associated with cumulative neurotoxicity, a shorter duration of therapy could spare toxic effects and health expenditures.

Methods: We performed a prospective, preplanned, pooled analysis of six randomized, phase 3 trials that were conducted concurrently to evaluate the noninferiority of adjuvant therapy with either FOLFOX (fluorouracil, leucovorin, and oxaliplatin) or CAPOX (capecitabine and oxaliplatin) administered for 3 months, as compared with 6 months. The primary end point was the rate of disease-free survival at 3 years. Noninferiority of 3 months versus 6 months of therapy could be claimed if the upper limit of the two-sided 95% confidence interval of the hazard ratio did not exceed 1.12.

Results: After 3263 events of disease recurrence or death had been reported in 12,834 patients, the noninferiority of 3 months of treatment versus 6 months was not confirmed in the overall study population (hazard ratio, 1.07; 95% confidence interval [CI], 1.00 to 1.15). Noninferiority of the shorter regimen was seen for CAPOX (hazard ratio, 0.95; 95% CI, 0.85 to 1.06) but not for FOLFOX (hazard ratio, 1.16; 95% CI, 1.06 to 1.26). In an exploratory analysis of the combined regimens, among the patients with T1, T2, or T3 and N1 cancers, 3 months of therapy was noninferior to 6 months, with a 3-year rate of disease-free survival of 83.1% and 83.3%, respectively (hazard ratio, 1.01; 95% CI, 0.90 to 1.12). Among patients with cancers that were classified as T4, N2, or both, the disease-free survival rate for a 6-month duration of therapy was superior to that for a 3-month duration (64.4% vs. 62.7%) for the combined treatments (hazard ratio, 1.12; 95% CI, 1.03 to 1.23; P=0.01 for superiority).

Conclusions: Among patients with stage III colon cancer receiving adjuvant therapy with FOLFOX or CAPOX, noninferiority of 3 months of therapy, as compared with 6 months, was not confirmed in the overall population. However, in patients treated with CAPOX, 3 months of therapy was as effective as 6 months, particularly in the lower-risk subgroup. (Funded by the National Cancer Institute and others.).

Figure 1.. Disease-free Survival with 3 Months versus 6 Months of Adjuvant Therapy.

Panel A shows the distribution of disease-free survival in the overall modified intention-to-treat population. At a median follow-up of 41.8 months, noninferiority of 3 months of treatment versus 6 months was not confirmed (hazard ratio, 1.07; 95% confidence interval [CI], 1.00 to 1.15; P = 0.11 for noninferiority of 3-month therapy; P = 0.045 for superiority of 6-month therapy). The 3-year rate of disease-free survival was 74.6% (95% CI, 73.5 to 75.7) in the 3-month therapy group, as compared with 75.5% (95% CI, 74.4 to 76.7) in the 6-month therapy group. Panel B shows the 3-year rate of disease-free survival according to subgroup, including treatment, tumor and nodal status, and risk.

Figure 2.. Disease-free Survival with 3 Months versus 6 Months of Therapy, According to Subgroup.

Among the subgroups of patients who were evaluated for disease-free survival, noninferiority of 3 months of therapy versus 6 months was confirmed only in the patients who had received CAPOX (hazard ratio, 0.95; 95% CI, 0.85 to 1.06) in the main analysis and in the patients at low risk (T1, T2, or T3 N1 disease) (hazard ratio, 1.01; 95% CI, 0.90 to 1.12) in an exploratory analysis. The test for interaction according to treatment was highly significant (P = 0.006), but the overall test for interaction according to risk group was not (P = 0.11). The interaction with therapy duration was not significant for tumor stage (P = 0.14) or for nodal stage (P = 0.91). The dashed vertical line indicates the noninferiority margin of 1.12 for the upper boundary of the two-sided 95% confidence interval.