Abstract Background The lung Continuous Allocation System (CAS), implemented in March 2023, replaced the Lung Allocation Score (LAS) and was designed to allocate donor lungs based on medical urgency and five-year post-transplant benefit with elimination of geographic boundaries. Although early analyses have described shifts in recipient characteristics and transport distances, the effect of CAS on the distribution of transplant activity among U.S. centers has not been evaluated. We reviewed volume redistribution among lung transplant centers in CAS compared to LAS era. Methods All adult (≥18 years), single-organ, first-time lung transplants performed between March 9, 2018 and June 30, 2025 were identified in the UNOS STAR thoracic dataset. Pediatric, redo, multi-organ transplants, and those listed in LAS but transplanted in CAS, were excluded. The LAS era (03/09/2018-03/09/2023) and CAS era (03/09/2023-06/30/2025) were compared across 71 U.S. transplant centers in 11 UNOS regions. Centers were stratified into quintiles of annualized transplant volume based on LAS-era activity. Primary outcome was the change in transplant share across quintiles (χ² test). Secondary analyses included within-center change in annualized volume (paired t-test/Wilcoxon) and linear and mixed-effects models assessing predictors of growth, with UNOS region as a random effect. Results A total of 19,492 adult lung transplants met the inclusion criteria (12,746 LAS; 6,746 CAS). The number of active centers remained constant (n = 71). National transplant share shifted significantly across volume quintiles (χ² = 142.5, df = 4, p 0.001): Q5 (highest volume) centers decreased from 45.3% to 37.7%, while Q4 (mid-high) centers increased from 24.4% to 29.7%. Median change in annualized volume per center was +2.6 cases/year (IQR -5.0 to + 11.8), with 58% of centers increasing activity. In regression models, only Q4 centers showed a significant increase compared with Q1 (+14 cases/year; 95 % CI 2.3-25.7; p = 0.019), whereas Q5 centers trended downward (-7.5 ± 5.8; p = 0.21). Mixed-effects modeling confirmed no regional clustering (region variance = 0). Conclusions Implementation of CAS was associated with a statistically significant redistribution of lung transplant activity across U.S. centers without geographic clustering. While overall center-level volume increased modestly, mid-volume programs exhibited the largest relative growth, and the highest-volume centers lost share. These findings suggest that CAS broadened national participation in lung transplantation and reduced procedural concentration without evidence of regional disparity. This abstract is funded by: None
Olson et al. (Fri,) studied this question.