The single-center retrospective analysis of steroid-free rmap regimen (ruxolitinib, montelukast, azithromycin, and pirfenidone) treating moderate-to-severe bronchiolitis obliterans syndrome (BOS).

Abstract Background: Bronchiolitis obliterans syndrome (BOS) is the most common late-onset pulmonary complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT), significantly impacting patient survival and quality of life. Currently, moderate-to-severe BOS is frequently complicated by recurrent infections, high mortality, and a lack of long-term effective treatments, resulting in low clinical remission rates. Objective:To retrospectively analyze the clinical efficacy and influencing factors of the steroid-free RMAP regimen (ruxolitinib, montelukast, azithromycin, and pirfenidone) in treating moderate-to-severe BOS. Methods:This study included 25 patients who developed moderate-to-severe BOS after allo-HSCT at our center between January 1, 2018, and December 31, 2024. The clinical outcomes and influencing factors of the RMAP regimen were retrospectively evaluated. Results: (1) Treatment response rate:The overall response rates at 3, 6, and 12 months were 48.0% (12/25), 56.0% (14/25), and 58.3% (14/24), respectively. Among responders (n=14), lung function, exercise tolerance, and overall health status improved (n=7) or remained stable (n=7). (2) Survival outcomes:With a median follow-up of 20 (6–80) months, 11 patients (44.0%) died, all due to severe pneumonia-related complications. Univariate analysis suggested a trend toward improved survival with prolonged RMAP treatment (P=0.049). (3) Steroid withdrawal: Among 23 patients with a history of long-term glucocorticoid use, 14 (56.0%) successfully discontinued steroids within 1 month of initiating RMAP, while 4 (16.0%) achieved a >50% dose reduction. (4) Safety:The regimen was well tolerated, with primary adverse events being grade 1–2 gastrointestinal reactions (n=19) and hematologic changes (n=16). No severe treatment-related adverse events were reported. Conclusion:The steroid-free RMAP regimen demonstrated promising efficacy in moderate-to-severe BOS, enabling rapid steroid withdrawal while improving quality of life and long-term survival. However, given the small sample size and retrospective design, further prospective studies are warranted for validation.