Molecular Response <1% BCR-ABL IS at 12 Months Is Associated with Improved Overall and Progression-Free Survival. the Randomized German CML-Study IV

Abstract 669 Introduction: The prognostic relevance of major molecular remission (MMR, Patients and Methods: We have analyzed 848 patients within the CML-Study IV (randomized comparison of imatinib 800 mg vs 400 mg vs 400 mg + IFN). BCR-ABL (IS) was determined by quantitative RT-PCR. Patients with atypical BCR-ABL transcripts were excluded from the analysis. Median observation time was 40 months (minimum 12). Landmark analyses have been performed at 12 months for overall and progression-free survival using 3 groups of response ( 1% BCR-ABL IS). Results: 341 patients achieved a BCR-ABL expression 1% by 12 months. Independent of treatment approach, the groups of patients achieving MMR and 0.1%- 1% BCR-ABL by 12 months (Figure). Conclusion: Faster and deeper response to imatinib-based treatment by 12 months revealed to be associated with improved PFS and overall survival. The critical cutoff level seems to be 1% BCR-ABL IS which has been shown to closely correlate with complete cytogenetic remission. Disclosures: Muller: Novartis: Honoraria, Research Funding. Schnittger: MLL Munich Leukemia Laboratory: Employment, Equity Ownership. German CML-Study Group: Deutsche Krebshilfe: Research Funding; Novartis: Research Funding; Roche: Research Funding; BMBF: Research Funding; Essex: Research Funding.