Quantification improves the prognostic value of CD38 expression in B-cell chronic lymphocytic leukaemia

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Abstract
Summary. Recent studies have shown that CD38 expressed as a percentage of the antigen positivity can predict prognosis and disease progression in patients with B‐cell chronic lymphocytic leukaemia (B‐CLL). The present study showed that quantification of CD38 expressed as antibody‐binding capacity (ABC) improves the prognostic value of the percentage of CD38 positivity in B‐CLL. In a cohort of 81 patients with B‐CLL, a level of CD38 expression of ≥ 30% and an ABC value of 250 proved statistically valid cut‐off points to predict disease progression (% CD38: P=0·0027; ABC: P < 0·0001). There was a positive and significant correlation between the percentage of CD38 expression and ABC (r=0·7; P < 0·0001). There was a better discrimination of survival using ABC rather than percentage CD38 positivity (P < 0·0001 compared with P=0·0027). Only ABC predicted for survival in patients under 60 years of age (P=0·0076) or with stage A disease (P=0·0195). Both percentage CD38 and ABC discriminated between time to first treatment for all patients but only ABC predicted time to treatment for stage A patients (P=0·0004). In conclusion, CD38 positivity is an important prognostic factor in B‐CLL. However, quantification of CD38 is superior to the percentage positivity and should be used clinically in conjunction with other variables of predictive value to identify B‐CLL patients that are likely to progress.