Evaluating the long-term effectiveness and safety of bosutinib versus imatinib in patients with newly diagnosed chronic phase chronic myeloid leukemia.

This study evaluated the long-term effectiveness and safety of bosutinib (Bosulif) versus imatinib (Gleevec) in patients with newly diagnosed chronic phase (CP) chronic myeloid leukemia (CML). The data showed that bosutinib had better effectiveness than imatinib in these patients.

CML is a type of cancer that starts in blood-forming cells of the bone marrow and enters the blood. Tyrosine kinase inhibitor (TKI) is a type of targeted therapy that works by blocking the growth of cancer cells. TKIs such as bosutinib and imatinib significantly improved survival for patients with CML.

Bosutinib is approved for the treatment of patients with newly diagnosed chronic phase CML. A previous study showed that bosutinib was more effective than imatinib in these patients. However, the long-term effectiveness and safety of bosutinib versus imatinib in patients with newly diagnosed CP-CML are still unknown.

This study involved 536 patients with CP-CML. Patients were randomly assigned into two groups. Group 1 included 268 patients who received 400 mg of bosutinib once daily. Group 2 included 268 patients who received imatinib daily. The average follow-up time was 55 months.

Molecular response to the drug was determined on a BCR-ABL1 international scale. BCR-ABL genes are found in cancerous cells. Lower percentages of BCR-ABL1 (10% or lower) are considered an optimal response. Major molecular response (MMR) is achieved when the BCR-ABL1 level is lower than 0.1%.

After 5 years, the MMR rate was 73.9% in group 1 versus 64.6% in group 2. Patients treated with bosutinib had a 57% higher chance of achieving MMR compared to those treated with imatinib. 

Treatment-related side effects were similar between the two groups. The most common side effects were heart and kidney related.

This study supported the use of 400 mg of bosutinib once daily as standard-of-care in patients with newly diagnosed CP-CML.

The patients knew which treatment they were getting. This might affect the conclusions. This study was funded by Pfizer, the manufacturer of bosutinib.