Evaluation of blood parameters for the monitoring of erythrodermic cutaneous T-cell lymphoma.

Background and Objectives: Erythrodermic cutaneous T-cell lymphomas are aggressive diseases posing diagnostic and therapeutic challenges. Numerous indicators for confirming diagnosis and disease-monitoring have been proposed. CD26-negativity of peripheral CD4 + T-cells has been reported to have these properties. Our aim was to test, if the CD4 + T-cell count, fraction of CD26-or CD7-negative CD4 + T-cells during the course of disease are valuable markers to predict therapeutic efficacy or disease progression in relation to changes in skin status. Patients and Methods: Retrospective cohort analysis of eleven patients treated at a tertiary referral centre. Statistics were done by linear regression analysis and logrank test. Results: Five patients displayed response to therapy in the skin, nine in the blood. Patients with cutaneous response showed a decrease of CD4 + T-cells, preceding the clinical response in most patients, whereas the percentage of CD26-negative T-cells changed first during clinical improvement. The calculated positive predictive values for response or progression were low for both CD4-count and CD26-expression. Conclusions: CD26 is not a reliable marker of either response or progression. As cutaneous response was always associated with a response in blood and not vice versa, we conclude, that the clinical status represents the most important parameter for guiding therapeutic decisions.