Prospective pooled analysis of six phase III trials investigating duration of adjuvant (adjuv) oxaliplatin-based therapy (3 vs 6 months) for patients (pts) with stage III colon cancer (CC): The IDEA (International Duration Evaluation of Adjuvant chemotherapy) collaboration.

LBA1 Background: Since 2004, 6 months (m) of oxaliplatin (oxali)-based treatment has been the standard of care as adjuvant therapy for stage III CC. Since oxali is associated with cumulative neurotoxicity, shorter duration of adjuv therapy could spare pts toxicity and lead to substantial saving in health expenditures. Methods: A prospective, pre-planned pooled analysis of 6 concurrently conducted randomized phase III trials (SCOT, TOSCA, Alliance/SWOG 80702, IDEA France (GERCOR/PRODIGE), ACHIEVE, HORG) was performed to evaluate the non-inferiority (NI) of 3m compared with 6m (ref) of adjuv FOLFOX/XELOX. The primary endpoint was disease-free survival (DFS), defined as time from enrolment to relapse, 2 CRC, and death (all causes). NI was to be declared if the 2-sided 95% confidence interval (CI) for DFS hazard ratio (HR 3m v 6m) estimated by a stratified Cox model was below 1.12. NI was examined within regimen and stage subgroups as pre-planned. Results: The analysis included 12,834 pts from 12 countries, accrued from 6/07 to 12/15. Stage distribution: 13% T1-2, 66% T3, 21% T4; 28% N2; 40% received XELOX. G3+ neurotoxicity was higher in the 6m v 3m arm (16 v 3% FOLFOX, 9 v 3% XELOX, p<0.0001). With a median follow-up of 39 mos, 3263 DFS events were observed. Overall, the 3 year DFS rate was 74.6% (3m) and 75.5% (6m), with estimated DFS HR of 1.07 (95%CI, 1.00-1.15). The 3m v 6m DFS HRs were 1.16 (95%CI, 1.06-1.26) and 0.95 (95% CI, 0.85-1.06) for FOLFOX and XELOX treated pts, respectively. The 3m v 6m DFS HRs were 1.01 (95%CI, 0.90-1.12) in T1-3 N1, and 1.12 (95%CI, 1.03-1.23) for T4 or N2 pts. Conclusions: While NI was not established for the overall cohort, NI of 3m v 6m oxali-based adjuv therapy was supported for XELOX. As each IDEA trial treated varying proportions of pts with XELOX (0 to 75%), the regimen interaction likely produced the differential outcomes observed between individual studies. Certain substages (T1-3 N1) also showed NI for 3m v 6m. These data provide a framework for discussions on risks and benefits of individualized adjuv therapy approaches. Support: U10CA180821, U10CA180882, U10CA180888, U10CA180835, INCA, PHRC2009, EME 09/800/34, HTA 14/140/84, CRUK C1348/A15960, JFMC. Clinical trial information: NCT01150045.

Duke Scholars

Author Donna Niedzwiecki Biostatistics & Bioinformatics, Division of Biostatistics