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Risk of relapse with imatinib (IM) at 5 years in advanced GIST patients: Results of the prospective BFR14 randomized phase III study comparing interruption versus continuation of IM at 5 years of treatment: A French Sarcoma Group study. I. Ray-Coquard, N. Bin Bui, A. Adenis, M. Rios,
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Risk of relapse with imatinib (IM) at 5 years in advanced GIST patients: Results of the prospective BFR14 randomized phase III study comparing interruption versus continuation of IM at 5 years of treatment: A French Sarcoma Group study. I. Ray-Coquard, N. Bin Bui, A. Adenis, M. Rios, F. Bertucci, S. Chabaud, D. Pérol, J. Y. Blay, A. Le Cesne for the French Sarcoma Group
Objectives Main endpoint Progression-free survival (PFS) Secondary endpoints Overall survival (OS) Response to imatinib re-start in the STOP arm Time to secondary resistance (TSR) in both arms
Summary of study steps • 1 year randomization From May 03 to March 04, 58 patients were randomized (32 in the STOP group). STOP group: 1-year PFS: 31% [CI95% , 16-47] CONT group: 1-year PFS: 85% [CI95%, 64-94] • 3 years randomization From June 05 to May 07, 50 patients were randomized (25 in the STOP group). STOP group : 1-years PFS : 32% [CI95% ; 15-50] CONT group : 1-years PFS : 92% [CI95% ; 72-98] • May 2007: amendment to address similar question after 5 years of imatinib treatment.
5 years randomization, statistical methods Since, Nov 07, 24 patients have been randomized (13 in the STOP group). Statistical consideration:in order to stop the study earlier ASAP in case of excess of relapses in the Stop arm : a Bayesian approach (study endpoint every 3 months) Bayesian Principle: Progression rate considered as a random parameter. Distribution updated at each analysis conditionally to previous data Probability of progression rate > in the STOP arm vs. CONT arm is estimated. If Prob (STOP > CONT) > 0.95: progression rate in STOP group is considered as statistically higher than in the CONT group. Adamina, M., G. Tomlinson, and U. Guller. "Bayesian statistics in oncology: a guide for the clinical investigator"; Cancer 115.23 (2009): 5371-81. Berry, D. A. "Bayesian clinical trials"; Nat.Rev.Drug Discov. 5.1 (2006): 27-36.
Results (2) • Density probability function • Date • Feb 2009: • STOP group: 1 prog / 6 • CONT group: 0 prog / 4 • Prob (STOP > CONT): p = 0.641 • Aug 2009: • STOP group: 3 prog / 10 • CONT group: 0 prog / 8 • Prob (STOP > CONT): p = 0.887 • May 2010: • STOP group: 7 prog / 11 • CONT group: 0 prog / 10 • Prob (STOP > CONT): p = 0.987
Results (3) Median follow-up : 11.9 months STOP group : median PFS : 12.6 months (CI95% = 8.6;21.8) CONT group : median not reached Log-rank test: p value = 0.0317
Conclusions • Imatinib stop at 5 yrs resulted in a higher rate of progression than imatinib maintenance in patients with advanced GIST in response or stabilized with imatinib. • Imatinib has to be given continuously until PD or intolerance in the population of non progressing advanced or metastatic GIST.