Abstract
6535 Background: The standard dose (SD) of imatinib for CP CML is currently 400 mg daily, but higher doses (HD) may be more effective. We conducted 2 consecutive trials using HD imatinib (i.e., 400mg twice daily) in previously untreated early CP CML pts. This is an updated analysis of the longer follow-up. Methods: A total of 175 previously untreated pts received HD imatinib. We compared the results with a previous study using SD imatinib (400mg/day) in untreated pts with early CP CML (N=50). Results: Cytogenetic and molecular responses were evaluable in 222 pts (N=49 at SD, 173 at HD) and 217 pts (N=46 at SD, 171 at HD), respectively. In HD group, Sokal risk classification was good in 69%, intermediate in 29%, and poor in 11% of pts. There were no differences in pre-treatment characteristics between two groups. The median age was 48 years in both groups. Median follow-up is 53 months for SD and 30 months for HD group. Patients treated with HD had a higher rate of complete cytogenetic responses (90% vs 78% with SD, p=0.03) and these occurred earlier, with 69% achieving this response after 6 months of therapy vs 45% with SD (p=0.001). The cumulative incidence of major molecular response was significantly better in HD group (p=0.03), and this response was also observed earlier in HD group: at 12 months 54% in HD and 24% in SD group had achieved this response (p=0.001). At 24 months, 19/70 (27%) evaluable pts with HD versus 3/31 (10%) of pts in SD group achieved complete molecular remission. Four pts (2%) in HD group and 4 pts (8%) in SD group have progressed to advanced phases (p=0.05). There was a trend in favor of the HD group for transformation-free-survival but it was not statistically significant (p=0.07). Overall survival is excellent in both groups (24 month survival, 99% with HD vs 98% with SD; p=0.24). Grade 3 or 4 hematologic toxicity was more frequent in HD group whereas extramedullary toxicity was similar in two groups. The median actual dose in HD group was 800 mg at 12 months, with 39% patients requiring dose reduction at some point. Conclusions: High-dose imatinib provides higher rates of complete cytogenetic responses and earlier molecular responses with some increase myelosupression. The long-term benefit of earlier responses remains to be demonstrated. [Table: see text]
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