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

Summary 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.