Imatinib shows continued excellent control of CML at 5 years

The IRIS study randomised 1,106 newly diagnosed patients with chronic phase chronic myelogenous leukaemia (CML) to either imatinib (IM) or interferon and cytosine arabinoside (Ara-C). An earlier publication had shown the benefit of using IM and the authors now presented mature data 5 years after the last patient was recruited. Crossover was allowed and 69% of patients had remained on the imatinib arm compared to 3% on Ara-C and interferon. The reasons for stopping IM were adverse events (6%), inadequate therapeutic effect (11%), other reasons (11%) and cross over to interferon and Ara-C (3%).At a median follow-up of 54-months, the overall survival was 89% (95% counting only CML related deaths) with a cumulative best response rate of complete haematologic response (CHR) of 98%, major cytogenetic response (MCyR, which included complete or partial cytogenetic responses) of 92% and complete cytogenic response (CCyR, defined as having no Ph+ metaphases) of 87%. An estimated 83% of patients had not progressed on treatment and 93% had not had progression to accelerated phase/blast crisis CML (AP/BC). The annual rate of progression to AP/BC in the first five years was 1.5, 2.8, 1.6, 0.9 and 0.6% respectively. The degree of response was important with 97% of the 436 patients achieving a MCyR at 12 months being free of progression to AP/BC at 54 months compared to only 81% of the 73 pts who did not achieve a MCyR at 12 months (p 3 log reduction of BCR-ABL transcript levels from the standardized baseline MMR within 12 months) progressed to AP/BC within 54 months. The authors concluded that this data confirmed the effectiveness of IM and that the rate of progression in the fourth year was lower than in each of the preceding three years. Good cytogenetic and molecular responses predicted good long-term outcomes.Reference...