Background and objectives: B-cell chronic lymphocytic leukemia (B-CLL) cells are variably distributed among the major lymphoid compartments contributing to the heterogeneous clinical presentation and course of this disease. In order to evaluate this variable distribution we propose a model for its clinical assessment.
Design and methods: We introduce the model for tumor distribution (TD) assessment based on TTM scoring system, where TD value represents percentage of total tumor mass infiltrating peripheral blood and bone marrow (TD=TM(1)/TTM). TD in B-CLL can be categorized into 3 subgroups: pure leukemia if TD=100%, predominantly leukemia if TD=50-99% and predominantly lymphoma TD<50%.
Results: Among 341 B-CLL patients there were 22.6%, 55.1%, 22.3%, pure leukemia, predominantly leukemia and predominantly lymphoma cases, respectively. TD parameter was strongly associated in univariate analysis with TTM size, Rai and Binet stages, spleen size and beta(2) microglobulin. TD was associated with response to therapy and survival, with higher TD values translated into higher response rates and longer survival. However, in univariate and multivariate Cox analysis TD displayed much stronger relationship with prognosis in female patients, where it is the strongest independent predictor of survival along with age and Binet stage.
Interpretation and conclusions: TD, a quantitative and simple clinical parameter, easily assessed in all patients, offers a reliable tool for evaluation of tumor cell distribution in B-CLL. It has independent and strong prognostic power in females, as opposed to males, possibly unmasking important, yet unrecognized, biological difference in B-CLL patients.