B-cell count and survival: Differentiating chronic lymphocytic leukemia (CLL) from monoclonal B-cell lymphocytosis (MBL) based on clinical outcome

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Blood First Edition Paper, prepublished online November 17, 2008; DOI

10.1182/blood-2008-09-176149.

B-cell count and survival: Differentiating chronic lymphocytic leukemia (CLL)

from monoclonal B-cell lymphocytosis (MBL) based on clinical outcome

Tait D Shanafelt*, Neil E. Kay, Greg , G. Call, Clive S Zent,

Diane F Jelinek, G. Morice, Boysen, Liam Zakko, Schwager,

L Slager, and Curtis A. Hanson

Mayo Clinic, Rochester, MN, United States

* Corresponding author; email: shanafelt.tait@... .

The diagnosis of CLL in asymptomatic patients has historically been based on

documenting a characteristic lymphocyte clone and the presence of lymphocytosis.

There are minimal data regarding which lymphocyte parameter(absolute lymphocyte

count[ALC] or B-cell count) and what threshold should be used for diagnosis. We

analyzed the relationship of ALC and B-cell count with clinical outcome in 459

patients with a clonal population of CLL phenotype to determine whether the CLL

diagnosis: 1)should be based on ALC or B-cell count; 2)what lymphocyte threshold

should be used for diagnosis; 3)whether any lymphocyte count has independent

prognostic value after accounting for biologic/molecular prognostic markers.

B-cell count and ALC had similar value for predicting treatment free

survival(TFS) and overall survival as continuous variables but, as binary

factors, a B-cell threshold of 11x109/L best predicted survival. B-cell count

remained an independent predictor of TFS after controlling for ZAP-70, IGHV,

CD38, or FISH results(all p<0.001). These analyses support basing the diagnosis

of CLL on B-cell count and retaining the size of the B-cell count in the

diagnostic criteria. Using clinically relevant criteria to distinguish between

MBL and CLL could minimize patient distress caused by labeling asymptomatic

individuals at low risk for adverse clinical consequences as having CLL.