Characterization of Spirometric Response to Standard-of-care Treatment in Lung Allograft Recipients With Bronchiolitis Obliterans and the Utility of Spirometric Criteria for Rescue Therapy: Implications for the Design of Risk-stratified Clinical Trials

Background. The spirometric response to standard-of-care (SOC) immunosuppressive therapy for the management of bronchiolitis obliterans syndrome (BOS) has been sparsely reported in the literature. Data from a Medicare-approved Registry were analyzed to characterize the effectiveness/durability of a wide range of SOC interventions to manage the decline of lung function and to validate the study spirometric criteria for initiation of rescue therapy. Methods. Lung transplant recipients with refractory BOS at 21 US collaborating centers were enrolled in the Registry. Data included both nonspirometric (eg, demographic, Immunosuppressive Regimens for management of BOS) and spirometric parameters (ie, FEV 1 measurements and derived indices). The utility of study forced expiratory volume in 1 s (FEV 1 ) criteria for treatment (ie, statistically significant rate of FEV 1 decline >30 mL/mo) was evaluated by comparing the spirometric course between participants who met or did not meet this criterion. Results. Only 21% of participants treated with SOC therapy had >50% decrease (76 ± 25% decrease) in the rate of FEV 1 decline. Although 51% of participants had a partial response (rate of FEV 1 decline decreased on average 71%), 49% of participants had a substantial increase (mean increase 224%). The FEV 1 criterion for treatment was able to identify 19% of participants (48/258) who achieved durable stabilization (ie, nonsignificant rate of FEV 1 <30 mL/mo) with SOC therapy. Conclusions. Patients with BOS have a widely variable response to SOC therapy. Our findings support the use of FEV1 rate of decline to assess response to SOC therapy and to assure appropriate assignment of participants with refractory BOS to rescue therapy treatment cohorts.