Association of change in clinical status and change in the percentage of the CD4+CD26- lymphocyte population in patients with Sézary syndrome.

Background: Because there are currently many effective therapies available for Sézary syndrome, close monitoring of disease progression is required in order for a clinician to know when to institute or change an intervention. It has been our clinical experience that changes in patients' CD4+CD26- T-cell populations of peripheral blood lymphocytes herald changes in their clinical status.

Objective: Our purpose was to evaluate whether a change in patients' CD4+CD26- population of T cells presages a change in their clinical status. We also sought to investigate the association between a change in T-cell populations that are CD4+CD7-, CD8+, CD56+, and the CD4+/CD8+ T-cell ratio and a change in the patient's clinical status.

Methods: We conducted a retrospective chart review analysis of 21 patients with Sézary syndrome who had flow cytometry, usually including levels of CD4+CD26-, CD4+CD7-, CD8+, CD56+, and CD4+/CD8+ ratios measured at two time periods, 12 weeks apart.

Results: We report two cases in which changes in patients' clinical status were preceded by several weeks by a change in their CD4+CD26- level. We report weak associations between a decreasing CD4+CD26- T-cell population, a decreasing CD4+CD7- population, an increasing CD56+ population, and an improving clinical status. We also report stronger associations between both a decreasing CD8+ population and an increasing CD4+/CD8+ ratio and a worsening clinical status.

Limitations: The study was limited by the number of patients and the time period over which the study was conducted. In addition, varying configurations of CD4+CD26- T-cell populations were observed that may have limited the utility of this measurement.

Conclusions: Flow cytometry assays of patients' blood and, in particular, measurement of the CD4+CD26- population of lymphocytes over time may be a valuable tool for monitoring patients with Sézary syndrome. There exist varying configurations of CD26 T lymphocytes that may cause differences in standards for what is considered positive and negative between observers. Further prospective analysis involving larger groups of patients is recommended.