Background: In this study, we aimed to determine a cutoff level for CD38 that would aid us in identifying chronic lymphocytic leukemia patients in need of early therapy and predicting patients at sufficiently low risk who would likely exhibit a rapid improvement; we also aimed to find out if CD38 expression would show variability during disease course and determine the extent of CD38 expression.
Methods: 124 patients were diagnosed with CLL. CD38 and ZAP-70 expression levels were measured with four color flowcytometry. Time from diagnosis to initial therapy was calculated for all patients. CD38 expression was studied for a second time during follow-up in 50 patients.
Results: For cutoff levels of 7%, 20%, and 30%, CD38 expressions were 61.3%, 25%, and 24.2%, respectively. At all three cutoff levels there were significant correlations with all parameters except age between CD38+ vs. CD38- groups (p < 0.001). The comparative rates of starting therapy for cutoff levels of 7%, 20%, and 30% in CD38+ and CD38- groups were 77.5% vs. 6.25%; 100% vs. 30.7%, and 100% vs. 31.5%, respectively (p < 0.001). Multiple Cox Proportional Hazards Regression analysis: for a cutoff level of 7%, survival was affected by STAGE, ZAP70, and CD38.
Conclusions: A CD38 cutoff level of 7% determined by standardized laboratory techniques is an important prognostic marker. However, the number and frequency of repeat measurements of CD38 expression, and cutoff level of CD38 expression that significantly predict disease prognosis should be further determined by future cohort studies.