The risk of thrombosis in patients with acute leukemia:: occurrence of thrombosis at diagnosis and during treatment

Background: Thromboernbolism can occur during acute leukemia, especially acute lymphoid leukemia (ALL) treated with L-asparaginase. Yet, most reports are anecdotical and scarce data are available on the risk of thrombosis in acute myeloid leukemia (AML). Objectives: To evaluate the risk of thrombosis in patients with acute leukemia. Patients and methods: Three-hundred and seventy-nine consecutive adult patients with newly diagnosed acute leukemia were recruited in an observational cohort study conducted from January 1994 to December 2003. Diagnosis was ALL in 69 patients, acute promyelocytic leukemia (APL; FAB subtype M3) in 31, and non-M3 AML in 279. All first or recurrent symptomatic thromboembolic events objectively diagnosed were recorded. Results: Twenty-four patients of the overall 379 (6.3%; 95% CI 4.1%-9.2%) had a first thrombosis, venous in 80% of the cases and arterial in 20%. At diagnosis, thrombosis was a presenting manifestation in 13 cases (3.4% of the whole cohort): 1.4% in ALL, 9.6% in APL, and 3.2% in non-M3 AML patients. Follow-up was carried out on 343 patients without thrombosis at diagnosis and further It thrombotic events (3.2%) were recorded. At 6 months from diagnosis, the cumulative incidence of thrombosis was 10.6% in ALL, 8.4% in APL, and 1.7% in non-M3 AML patients. The patients who received L-asparaginase had a 4.9-fold increased risk of thrombosis in comparison with those who did not (95% CI 1.5-16.0). The fatality rate due to thrombosis was 0.8%. Conclusions: In patients with acute leukemia, the risk of thrombosis is not negligible. Thombosis can be a presenting symptom at diagnosis in a significant portion of cases with APL (9.6%) and non-M3 AML (3.2%); a similar rate of thrombosis can occur during the subsequent course of the disease. The incidence of symptomatic thrombosis at diagnosis is relatively low in ALL patients (1.4%), but is significantly increased by further treatment up to 10.6%. Strategies of antithrombotic prophylaxis should be investigated in this setting.