Lenalidomide and dexamethasone for Rosai-Dorfman disease: a single arm, single center, prospective phase 2 study

Rosai-Dorfman disease (RDD) is a rare heterogeneous histiocytic disorder lacking standardized first-line treatment.

This single-center, phase 2 prospective study enrolled 13 newly diagnosed and 10 recurrent RDD patients from June 2021 to March 2023 at Peking Union Medical College Hospital (Beijing, China). Lenalidomide 25 mg days 1-21 plus dexamethasone 40 mg days 1, 8, 15, 22 was administered in 28-day cycles, totaling 12 cycles. The primary endpoint was progression-free survival (PFS). Secondary endpoints were overall response rate (ORR) to lenalidomide and dexamethasone (RD) regimen, toxicity, and overall survival (OS) measured from RD start to death or last follow-up. OS and PFS were estimated according to Kaplan-Meier survival analysis and compared with the log-rank test. For OS and OR rate, 95% confidence limits were obtained using the Clopper-Pearson method, with standard methods used for PFS. p < 0.05 was considered statistically significant. The trial was registered with ClinicalTrials.gov (NCT04924647).

The median age was 44 years (IQR 35-54). All patients had extranodal RDD. MAPK pathway alterations occurred in 6/18 (33%). Elevated IL-6 and TNF-α were found in 39% (n = 9) and 70% (n = 16), respectively. All patients received ≥6 cycles (median 12, range 6-12, IQR 10-12). The ORR was 87% (20/23, 95% CI 66%-97%), 30% (n = 7) complete remission, 57% (n = 13) partial remission). Treatment with RD significantly decreased median serum levels of both IL-6 (from 5.9 (IQR 4.2-8.7) to 2.9 (IQR 2.1-5.9) pg/mL, p = 0.031) and TNF-α (from 12.2 (IQR 8.6-17.9) to 8.3 (IQR 6.1-10.5) pg/mL, p = 0.0012). With a median 26 months follow-up (range 6-28, IQR 16-28), 4 patients relapsed and none died. Two-year OS and PFS were 100.0% (95% CI 85%-100%) and 69.0% (95% CI 51%-94%), respectively. No grade 3-4 adverse events or discontinuations due to adverse events occurred. Twelve patients (n = 12, 52%) had grade 1-2 hematological toxicity. Other toxicities included constipation (n = 2, 9%), glucose intolerance (n = 2, 9%), edema (n = 2, 9%), insomnia (n = 1, 4%), and tremor (n = 1, 4%).

Lenalidomide and dexamethasone regimen is an effective and safe regimen for newly diagnosed and recurrent RDD.

National Natural Science Foundation of China, Beijing Natural Science Haidian frontier Foundation Funding, and the National High Level Hospital Clinical Research Funding.