Economic Burden of Bronchiolitis Obliterans Syndrome (BOS) Following Allogeneic Hematopoietic Stem Cell Transplant (alloHSCT) in Patients with Commercial Insurance in the United States
Authors: Sacks Naomi , Healey Bridget , Cyr Philip , Batt Katharine , Henig Noreen Roth 
Published: November 2019

Background
Bronchiolitis obliterans syndrome (BOS), also known as respiratory chronic Graft versus Host Disease (cGvHD), is an obstructive airway disease of the lungs following alloHSCT that has significant morbidity and mortality. BOS is characterized by T-cell mediated inflammation and fibrosis of bronchiolar walls that reduces the diameter of the bronchioles resulting in progressive and irreversible airflow obstruction.
BOS is a well described complication following lung transplant and can also be a complication following alloHSCT, with similar histopathology and clinical symptoms. There is currently no approved therapy for the treatment of BOS. While data on alloHSCT costs are available (Milliman 2017; Broder et al., 2017), little is known about the impact of BOS on healthcare resource use (HRU) and costs in alloHSCT. The aim of this study is to quantify the economic burden of BOS in alloHSCT patients.
Methods
We performed a retrospective analysis of commercial claims data from the IQVIA PharMetrics Plus™ database for patients aged 0-64 who were treated with alloHSCT from 1/1/2007 to 9/30/2017. Patients were observable 12 months before and after index alloHSCT. Those who developed BOS were identified using International Classification of Disease (ICD) diagnosis codes (ICD-9: 491.8, 491.9, 515, 516.34, 561.8; ICD-10: J41.8, J42, J84.09, J84.89, J84.115) and propensity score matched to identify patients who did not develop BOS after alloHSCT. We calculated mean annual per patient rates of hospitalizations, tests and treatments for BOS, as well as costs in the follow-up year for inpatient admissions, Emergency Department (ED) and non-ED outpatient visits, and prescription medications. Costs for the index HSCT were included in the first follow-up year costs. All analyses were repeated for the subset of patients observable in the second post-alloHSCT year. The effect of BOS was estimated as the difference in HRU and costs between the matched BOS and non-BOS alloHSCT patients.
Results
We identified 161 alloHSCT patients with commercial insurance coverage who developed BOS. A majority were male (60%). Mean age was 51.0 yrs (+/- SD: 12.13); a small proportion (2%) were under age 18. We also identified 161 matched alloHSCT patients who did not develop BOS. More BOS patients were diagnosed with leukemias or lymphomas compared with non-BOS patients (94% vs. 84%) in the pre-alloHSCT year, and more had pulmonary disease (asthma or COPD; 24% vs. 16%). No other differences were statistically significant at p&gt;0.05.
In the year following alloHSCT, BOS patients had higher mean per patient annual numbers of inpatient admissions (3.9 [+/- SD: 3.3] vs. 2.6 [+/- SD: 2.5]). More BOS patients received lung function testing, including spirometry (60% vs. 42%), and more were treated with ventilation, oxygen therapy or pulmonary rehabilitation (61% vs. 39%). Costs were higher for BOS patients ($560,048 vs. $408,764), with inpatient costs responsible for most of this difference ($446,622 vs. $300,146). Lung function test costs were over 3 times as high for BOS patients ($35,744 vs. $10,192) and lung function treatment costs 2.5 times as high ($31,761 vs. $7,994). Costs for patients observable in the second post-alloHSCT year were considerably lower, as the costs for the initial alloHSCT costs were reflected in the first year expenditures. Nonetheless, costs remained higher for BOS patients ($72,829 vs. $43,665), with higher inpatient, outpatient and prescription drug costs and HRU (Table, Figure).
Conclusion
AlloHSCT patients who develop BOS in the U.S. have higher rates of hospitalization and have more lung function tests and treatments, compared with alloHSCT patients with no diagnosis of BOS in the first 1-2 years post-alloHSCT. These higher rates of healthcare service use are accompanied by mean annual per patient costs that are $151,000 higher in the first post-alloHSCT year.

Disclosures
Sacks: Breath Therapeutics Inc.: Other: Employee of Precision Health Economics (PHE). PHE received funding from Breath Therapeutics for this research. . Healey:Breath Therapeutics Inc.: Other: Employee of Precision Health Economics (PHE). PHE received funding from Breath Therapeutics for this research. . Cyr:Breath Therapeutics Inc.: Other: Employee of Precision Health Economics (PHE). PHE received funding from Breath Therapeutics for this research. . Batt:Breath Therapeutics Inc.: Other: Scientific Adviser to Precision Health Economics (PHE). PHE receieved funding from Breath Therapeutics for this research.. Henig:Breath Therapeutics Inc.: Employment.