Persistence of complete molecular remission in chronic myeloid leukemia after imatinib discontinuation: Interim analysis of the STIM trial

Abstract

7084 Background: Imatinib (IM) has greatly improved survival in chronic myeloid leukemia (CML). However, IM must be continued for an indefinite period of time. A multicenter trial “Stop Imatinib” (STIM) was initiated in July 2007, in order to evaluate the persistence of complete molecular remission (CMR) after stopping IM and determine factors associated with CMR persistence. Methods: Inclusion criteria were IM treatment duration ≥3 years and sustained CMR, defined as BCR-ABL transcripts below a detection threshold of a 5-log reduction (undetectable by RQ-PCR) for ≥2 years. Molecular relapse was defined as RQ-PCR positivity confirmed on 2 successive occasions. In case of relapse, pts were rechallenged with IM at 400 mg daily. Molecular monitoring was performed according to international recommendations. Results: Sixty-nine pts were recruited among which 60 with a follow-up >1 month, including 22 males and 38 females. Median age was 62 (29–80), 31 pts had been treated with IFN prior to IM and 29 with IM frontline (de novo). Median follow-up was 5 months (1–16). Relapse occurred in 37 pts within 6 months of IM discontinuation. Only 1 pt relapsed after 6 months (M7). All patients in molecular relapse were sensitive to IM reintroduction. At last follow-up in December 2008, CMR was sustained in 8 pts at M14 and 3 pts at M16. No differences in terms of demography, duration of IM treatment and CMR duration were found between pts who relapsed and those who did not. At M9, the probability of persistent CMR was 46% (95% CI: 32–59%), 53% (95% CI: 33–69%) for previously IFN-treated pts and 39% (95% CI: 20–58%) for de novo pts (p = 0.54). A trend for a lower probability of relapse in low Sokal score pts was observed. Conclusions: Our data confirm that CMR can be long-lasting after discontinuation of IM. Using stringent criteria, it is possible to stop IM in patients with sustained CMR, even in those treated with IM as a single agent. Updated follow-up will be presented. No significant financial relationships to disclose.