The prospective, randomized SPIRIT trial, conducted in France, compared long-term outcomes with imatinib and imatinib combinations in patients with chronic-phase chronic myeloid leukemia (CML). The findings from this four-arm study, published in Leukemia, found that long-term survival rates were similar across imatinib dose levels, but response rates were significantly higher with imatinib 400 mg plus pegylated interferon alfa-2a.
The SPIRIT trial, which started in 2003, randomized 787 patients with treatment-naïve CML to receive either:
- imatinib 400 mg
- imatinib 600 mg
- imatinib 400 mg + cytarabine
- imatinib 400 mg + pegylated interferon alfa-2a
The median overall follow-up was 13.5 years (range = 3 months to 16.7 years). At 15 years, the overall and progression-free survival rates were similar across arms, ranging between 82% and 85% for overall survival and 79% and 84% for progression-free survival.
The rate of major molecular response at 12 months and deep molecular response (MR4) over time were significantly higher with the combination imatinib 400 mg + pegylated interferon alfa-2a (p = 0.0001 and p = 0.0035, respectively).
The authors noted that progression to advanced phases and secondary malignancies were the most frequent causes of death.