Weight Change in Underweight or Obese Patients Awaiting Lung Transplantation Does Not Impact Post-Trasplant Survival

BACKGROUND: Lung transplantation remains the definitive treatment for end-stage COPD, respiratory complications of cystic fibrosis, and interstitial lung diseases. However, long-term survival after lung transplantation remains poor, with an overall 5-year survival rate of 54%. Initial selection of lung transplant candidates includes evaluation of body mass index (BMI), since obesity is a relative contraindication to lung transplantation. However, BMI changes occurring while waiting for transplantation may not reflect initial listing BMI and may be associated with poorer long-term survival. OBJECTIVE: To determine the effects of pre-transplant BMI change on long-term survival following lung transplantation. METHODS: A retrospective chart review of adult lung transplantations performed between January 2004 and May 2016 was conducted. Patient demographics, survival status, and date of death, hours on the mechanical ventilator (MV hours), and ICU length of stay (ICU LOS) were collected. Cases were categorized as underweight (BMI < 20 kg/m2) or obese (BMI > 30 kg/m2), with change in BMI from time of listing to time of transplantation as subsets. Kaplan-Meier plots were constructed to summarize differences in overall survival between BMI groups. The log rank test was used to assess differences between survival curves. A Z-test using Greenwood's formula was performed to compare post-transplant survival rates at 1, 3, and 5 years. P-values were adjusted using the false discovery rate (FDR). RESULTS: There were 460 cases included in this study. The group sizes were as follows: underweight and lost weight (BMI < 20 kg/m2 -), 35; underweight and gained weight (BMI < 20 kg/m2 +), 47; obese and lost weight (BMI > 30 kg/m2 -), 61; obese and gained weight (BMI > 30 kg/m2 +), 25. Patients with initial BMI between 20.1 kg/m2 - 29.9 kg/m2 were assigned to the control group (n = 292). There were no differences in 1-year, 3-year, or 5-year survival rates (1-year: control 87.6%; BMI < 20 kg/m2 -, 91.3%; BMI < 20 kg/m2 + 86.4%; BMI > 30 kg/m2 - 93.%; BMI > 30 kg/m2 + 71.2%; all comparisons non-significant [NS]) (3-year: 71.1%; 49.2%; 54.1%; 69.8%; 56.6%, NS) (5-year: 61.1%; 35.1%; 45.9%; 49.1%; 50.9%, NS). Kaplan-Meier plots similarly showed no differences in overall survival (p = 0.203). There were no significant differences among the groups in ICU LOS or MV hours. CONCLUSION: Weight change in obese or underweight patients prior to lung transplantation does not affect overall survival. Therefore, BMI > 30 kg/m2 at the time of listing may not be a relative contraindication to lung transplantation.