Background: The serum concentration of soluble α chain of the interleukin-2 receptor (sIL-2R) correlates with tumor burden in cutaneous T- cell lymphoma (CTCL). Therefore the sIL-2R level may be useful to monitor the condition of patients treated with extracorporeal photopheresis or other treatments. Objective: Our goal was to determine the utility of serum sIL-2R as a test in monitoring of patients with advanced CTCL. Methods: Serum sIL- 2R was measured serially in 36 patients with advanced CTCL treated with extracorporeal photopheresis and other modalities (interferon alfa, methotrexate, topical nitrogen mustard, electron beam). Results: Serum concentrations of sIL-2R as well as lactate dehydrogenase (LDH) correlated strongly with lymph node size, but only sIL-2R correlated significantly with the severity of skin manifestations in erythrodermic patients. In addition, serum sIL-2R, but not LDH, was significantly higher in patients with nodal involvement. The level of sIL-2R also was significantly higher in patients with large-cell transformation in the skin or lymph nodes compared with patients without transformed disease. During treatment, serum concentrations of both serum sIL-2R and LDH correlated with changes in clinical status, but only sIL-2R showed statistically significant differences in mean levels for different relative global response scores. Pretreatment levels of both sIL- 2R and LDH correlated significantly with survival, but only sIL-2R retained significance when both were entered into the Cox proportionate hazards model. Conclusion: The concentration of serum sIL-2R correlates well with disease status and is more useful than LDH or Sezary cell counts to monitor clinical change in patients with advanced CTCL. Moreover, our data suggest that sIL- 2R is produced at a relatively low rate by tissue-based lymphoma cells, and that large-cell transformation in CTCL results in marked increase in sIL-2R production in some patients.
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