Phase II trial of intermittent high-dose recombinant interferon alfa-2a in mycosis fungoides and the Sézary syndrome.

We previously demonstrated that recombinant interferon alfa-2a (IFN-alfa) in a dose of 50 X 10(6) U million units (MU)/m2 intramuscularly (IM) three times per week has efficacy against mycosis fungoides (MF) and the Sézary syndrome (SS). However, this regimen given to patients with refractory disease was uniformly complicated by toxicities requiring major dose reductions. The present study was designed to determine if intermittent high-dose IFN-alfa would preserve efficacy and decrease toxicity in a similar patient population. Twenty-four patients with advanced disease refractory to one or more standard therapies received IFN-alfa, 10 MU/m2 IM on day 1 followed by 50 MU/m2 IM on days 2 to 5 every 3 weeks; after the first four cycles, stable and partially responding patients underwent dose escalation to twice the starting dose. One complete (CR) and six partial responses (PRs) were observed (response rate, 29%; 95% confidence interval, 13% to 51%) lasting 4 to 19 months (median, 8 months). No improvement in objective response was seen in the eight patients who received dose escalation. Dose reductions were necessary in eight of 22 patients receiving one or more cycles of therapy. Weighted mean dose rate intensity for patients on this study over the first four cycles of treatment was 65.5 MU/m2/wk compared with 73.2 MU/m2/wk over the first 12 weeks of treatment in patients from the previous study, in which all 19 patients receiving more than 1 week of treatment required dose reduction. IFN-alfa is effective against previously treated MF and the SS and is better tolerated on this intermittent schedule.