In stage III colon cancer, can adjuvant oxaliplatin-based chemotherapy safely be shortened from 6 months to 3 months without unacceptable loss of disease control? [IDEA Collaboration]
In stage III colon cancer, can adjuvant oxaliplatin-based chemotherapy safely be shortened from 6 months to 3 months without unacceptable loss of disease control?
Absolute Effect
Five-year OS was 82.4% with 3 months versus 82.8% with 6 months; HR 1.02 (95% CI 0.95–1.11). Overall non-inferiority was not formally established (FDR-adjusted P=.058).
Absolute effect: Five-year OS differed by only 0.4 percentage points overall (82.4% vs 82.8%). Updated DFS HR was 1.08 (95% CI 1.02–1.15); 3-year DFS was 74.6% vs 75.5%.
NNT: not applicable. This is a non-inferiority/de-escalation question; the small numerical OS difference must not be labelled a benefit of either duration.
NNH: not applicable as harm from 6 months is better expressed as an absolute reduction in toxicity with 3 months. In the IDEA/France toxicity dataset, grade 3–4 neuropathy was 8% with 3 months vs 25% with 6 months; the corresponding NNT-for-harm-prevention is about 6 for avoiding one grade 3–4 neuropathy case.
Follow-up: Median follow-up 72.3 months for final OS.
Clinical results and treatment burden
- Intervention: Three versus six months of adjuvant FOLFOX or CAPOX. Regimen choice was not randomized in the pooled analysis.
- Principal toxicity: The clinically central cumulative toxicity was oxaliplatin-induced sensory peripheral neuropathy. Across the IDEA programme, shorter therapy substantially reduced neuropathy; regimen and risk group modified the efficacy trade-off.
- Other efficacy/recurrence findings: CAPOX and FOLFOX behaved differently. Three months of CAPOX was compatible with non-inferiority, whereas three months of FOLFOX was not. Low-risk T1–3N1 disease was more tolerant of shortening than T4/N2 disease.
- Quality of life: The main patient-centred advantage is reduced cumulative neuropathy, treatment time, clinic visits and cost; long-term neurotoxicity is clinically important.
Eligibility and clinical context
12,834 patients with stage III colon cancer and ECOG performance status 0–1 from six prospective randomized phase III trials; regimen was FOLFOX or CAPOX.
Limitations and maturity: The pooled analysis is not a single conventional RCT: regimen choice was clinician-selected and individual component trials differed. The result cannot be reduced to '3 months is equivalent to 6 months' for every patient.