Incidence of spontaneous remission in patients with CD25-positive mycosis fungoides/Sézary syndrome receiving placebo.

BACKGROUND

Spontaneous remission is recognized in mycosis fungoides (MF) and Sézary syndrome (SS).

OBJECTIVE

We analyzed the outcome of 44 patients with previously treated CD25-positive (CD25+), recurrent/persistent MF/SS randomly assigned to receive placebo as part of a phase III trial.

METHODS

This trial investigated the efficacy and safety of two doses of denileukin diftitox in patients with MF/SS who had received up to 3 prior therapies. The primary end point was overall response rate. Multivariate regression analyses were used to assess the relationship between baseline covariates and clinical outcomes.

RESULTS

The overall response rate was 15.9% for placebo recipients (complete response: 2.3%; partial response: 13.6%), reflecting the baseline rate of disease remission that can be expected in a clinical trial. The median progression-free survival (PFS) in the placebo arm was moderately short at 4.4 months compared with the active-agent arm but important to consider in the context of recent single-arm phase II studies of other therapies for MF/SS that report PFS of approximately 6 months. Multivariate analyses identified no significant effects of any baseline factors on either overall response rate or PFS, although there was a trend toward poorer PFS with advanced age. Because sepsis occurred significantly more often in the placebo arm versus the active-treatment arm, the role of antibiotics in causing remission cannot be discounted (6.8% vs 0%; P < .05).

LIMITATIONS: This study had a relatively small sample size, yielding a wide 95% confidence interval.

CONCLUSION

The results may serve as a useful comparator for other active-treatment studies of MF/SS that lack a placebo-control arm.