Leukocytosis, thrombosis and early mortality in cancer patients initiating chemotherapy.

BACKGROUND

Leukocytosis has been associated with thrombosis and mortality in cancer patients. We explored the association of leukocytosis with venous thromboembolism (VTE) and early mortality in cancer patients initiating chemotherapy.

METHODS

Data from a prospective, multicenter observational study of treatment-related complications in 4,405 ambulatory cancer patients initiating chemotherapy was used for this analysis. The association of leukocytosis, VTE and mortality during the course of chemotherapy was evaluated in univariate and multivariate analysis.

RESULTS

Ninety-three patients (2.1%) developed VTE and 134 (3%) died over a median follow up of 75 days (range 0-384). Of 4391 patients with available baseline white blood cell (WBC) count, 561 (12.8%) had elevated pretreatment leukocyte counts, defined as WBC > 11 x 10(9) cells/L. VTE occurred in 25 of 561 patients (4.5%) with baseline leukocytosis compared to 68 of 3830 (1.8%) with WBC <or= 11 x 10(9) cells/L (P < 0.0001). Baseline leukocytosis was associated with VTE by multivariate analysis as well (HR 2.1, 95% confidence interval 1.3-3.4, p = 0.003). Forty one patients (7.3%) with leukocytosis died compared to 92 (2.4%) with WBC <or= 11 x 10(9) cells/L (P < 0.0001). Baseline leukocytosis was associated with early mortality by multivariate analysis as well (HR 2.2, 95% confidence interval 1.5-3.3, p < 0.0001). Mortality was greatest in patients with both leukocytosis and VTE. In multivariate analysis several factors were predictive of leukocytosis.

CONCLUSIONS

Elevated WBC, particularly neutrophils, is strongly associated with increased risk of VTE and mortality in cancer patients receiving systemic chemotherapy. Further studies are needed to elicit the mechanisms involved.