Results of Imatinib Therapy In Patients with Early and Late Chronic-Phase Chronic Myeloid Leukemia In a South Brazilian Cohort.

Imatinib treatment for Chronic Myeloid Leukemia (CML) was first introduced in Brazil in 2001, initially used as second line therapy for patients resistant or intolerant to interferon (IFN). In 2008 imatinib was adopted as front-line therapy for chronic-phase (CP-CML) and clinical experience is improving since then, but little is known about the result of its introduction in our clinical practice.

To evaluate the impact of imatinib treatment in the outcomes of a cohort of CP-CML and the prognostic significance of Sokal and Hasford scores and late-onset treatment.

We conducted a retrospective study in a cohort of patients with CP-CML from a south Brazilian database. All patients received imatinib 400mg as first or second-line therapy. Patient evaluation and response criteria followed the European LeukemiaNet. The outcomes were response to treatment, event-free survival (EFS) and overall survival (OS).

We analyzed data from 185 pts with CP-CML diagnosed since 1990. The median age at diagnosis was 48 years (4 – 85). The median time from diagnosis to imatinib was 7 months (0 – 178) and 29% of pts had more than 12 months lapse. Prior therapy with IFN was used in 70% pts. All pts had a minimum follow-up of 12 months. At baseline, 57 pts (31%) were in complete hematological response (CHR) due to the use of previous treatment. Of the 127 pts not in CHR at baseline, 98% achieved CHR early during imatinib treatment. 177 pts had cytogenetic evaluation during treatment and 9 pts were in complete cytogenetic response (CCyR) due to the use of previous IFN. Of the 168 pts not in CCyR at baseline, 86,4% achieved a major cytogenetic response (MCyR) during imatinib treatment (84% had a CCyR and 2,4% had a partial cytogenetic response). The rate of pts achieving MCyR any point during treatment differed significantly in the low, intermediate and high risk Sokal score groups (97%, 81% and 78% respectively, P=0,04), but not in the Hasford score groups (90%, 85% and 72%, P=0,22). Minor cytogenetic response was seen in 3,6% of pts, minimal cytogenetic response in 6% and 9,5% had no cytogenetic response. The median time to a MCyR was 9 months, with 62% of pts achieving MCyR at 12 months. The rate of pts achieving MCyR in 12 months differed significantly between pts who start imatinib before 12 months from diagnosis (68%) and those late treated (47%, P=0,02). Evaluation of minimal residual disease at the molecular level was available for 155 pts: 25,5% of pts had a complete molecular response (CMR), 43% had a major molecular response (MMR) and 2 pts were in MMR at baseline due to previous IFN. The projected EFS and OS rates at 4 years were, respectively, 68% and 92% after a median follow-up time of 4 years. The rate of EFS differed significantly in the low, intermediate and high risk Sokal score groups (80%, 66% and 52% respectively, P=0,04), but not in the Hasford score groups (78%, 62% and 44%, P=0,09). During treatment with imatinib, 120 pts (65%) had a register of any grade hematologic adverse event (21% being grades 3 or 4) and 165 pts (90%) had a register of any grade nonhematologic adverse event (9,3% being grades 3 or 4). Of the 185 pts who received treatment, 134 (72%) continue to receive imatinib and 51 (28%) discontinued treatment. The reasons for discontinuation were: 11 (6%) pts had drug-related adverse events (3 [1,6%] hematologic and 8 [4,3%] nonhematologic), 17 (9,2%) had disease progression (5 [2,7%] loss of CHR, 10 [5,4%] loss of CCyR, 2 [1%] had progression to accelerate or blastic phase), 22 (11,9%) had treatment failure (3 [1,6%] had no CHR, 13 [7%] had no CCyR and 6 [3,2%] had no MMR), 1 pt (0,5%) discontinued due to comorbidity. For the 51 (100%) pts that discontinued imatinib, 31 (61%) switched to dasatinib, 17 (33%) to nilotinib, 1 (2%) to hydroxyurea, 1 (2%) to other treatment and 1 (2%) remained without treatment. Sixteen pts (8,6%) died during imatinib treatment or during long-term follow-up after discontinuation of imatinib.

In our population of CP-CML pts treated with imatinib, a majority of patients achieved complete cytogenetic and major molecular responses, with a prolonged of OS and EFS and good safety profile. Sokal score showed better prognosis prediction than Hasford. Early onset of imatinib therapy led to better outcomes and justifies imatinib as front-line treatment of our patients.

No relevant conflicts of interest to declare.