Actual Size Mismatch in Lung Transplantation for Restrictive Lung Disease

PurposeDonor to recipient predicted total lung capacity (TLC) ratio is increasingly used for size matching in lung transplantation. This can overlook significant reductions in the actual TLC frequently seen in restrictive lung diseases. Forced vital capacity (FVC) is a useful surrogate for actual TLC, with proportionate decreases with progression of restrictive conditions. Analyzing donor predicted:recipient actual FVC could better predict actual lung size mismatch.MethodsThe UNOS database was used to identify 7,572 patients with restrictive lung disease undergoing isolated bilateral lung transplantation from 2005 to 2021. Lung size mismatch was quantified by donor:recipient FVC ratio, and patients were divided into quintiles. Multivariable cox regression was used to assess the relationship between size mismatch and all-cause mortality, adjusting for patient, donor and center baseline characteristics including lung allocation score (LAS) and degree of recipient FVC decline. Restricted cubic splines were used to assess the non-linear relationship between the FVC ratio and relative mortality hazard. Median follow-up was 2.6 (range 0-15) years.ResultsThe median age of the cohort was 59 (Interquartile range (IQR) 53-64) years, 32.5% (n=2,464) were female and the median LAS was 47.1 (IQR 39.7-67.3). The median FVC ratio was 2.4 (range 1.1-5.3). Overall unadjusted 10-year survival was 37.3% (95% confidence interval (CI) 35.5-39.2). The primary cause of death was graft failure in 19.0% (n=532) cases. The highest quintile of FVC ratio was an independent predictor of mortality in multivariable analysis (hazard ratio 1.2, 95% CI 1.1-1.4). Spline analysis indicated that an FVC ratio >3.45 predicted significantly worse survival (Figure 1), corresponding to the 1,043 (14%) most oversized patients.ConclusionOversizing with respect to FVC results in worse long-term survival despite adjustment for baseline characteristics, emphasizing the importance of considering recipient actual TLC in donor-recipient matching. Donor to recipient predicted total lung capacity (TLC) ratio is increasingly used for size matching in lung transplantation. This can overlook significant reductions in the actual TLC frequently seen in restrictive lung diseases. Forced vital capacity (FVC) is a useful surrogate for actual TLC, with proportionate decreases with progression of restrictive conditions. Analyzing donor predicted:recipient actual FVC could better predict actual lung size mismatch. The UNOS database was used to identify 7,572 patients with restrictive lung disease undergoing isolated bilateral lung transplantation from 2005 to 2021. Lung size mismatch was quantified by donor:recipient FVC ratio, and patients were divided into quintiles. Multivariable cox regression was used to assess the relationship between size mismatch and all-cause mortality, adjusting for patient, donor and center baseline characteristics including lung allocation score (LAS) and degree of recipient FVC decline. Restricted cubic splines were used to assess the non-linear relationship between the FVC ratio and relative mortality hazard. Median follow-up was 2.6 (range 0-15) years. The median age of the cohort was 59 (Interquartile range (IQR) 53-64) years, 32.5% (n=2,464) were female and the median LAS was 47.1 (IQR 39.7-67.3). The median FVC ratio was 2.4 (range 1.1-5.3). Overall unadjusted 10-year survival was 37.3% (95% confidence interval (CI) 35.5-39.2). The primary cause of death was graft failure in 19.0% (n=532) cases. The highest quintile of FVC ratio was an independent predictor of mortality in multivariable analysis (hazard ratio 1.2, 95% CI 1.1-1.4). Spline analysis indicated that an FVC ratio >3.45 predicted significantly worse survival (Figure 1), corresponding to the 1,043 (14%) most oversized patients. Oversizing with respect to FVC results in worse long-term survival despite adjustment for baseline characteristics, emphasizing the importance of considering recipient actual TLC in donor-recipient matching.