Title:
Zonal organ allocation system and its impact on long-term outcomes after lung transplantation: a propensity score matched analysis†.

Abstract:
Zonal organ allocation system comprises organ procurement by teams within a specific geographical area of each retrieval team. Therefore, in a substantial number of cases organs are retrieved by 'foreign' teams and are sent for transplantation to the implanting centre. The aim of this study was to assess the impact of zonal organ allocation system on early- and long-term outcomes after lung transplantation (LTx).
Included were 331 consecutive patients who underwent LTx performed at Harefield Hospital between January 2007 and January 2015. Recipients were divided into two groups depending on the organ retrieval team: 204 (61.6%) patients were transplanted using lungs procured by our institutional team (institutional group), whereas 127 (38.4%) organs were retrieved by other teams (external group) from experienced transplant centres in the UK. To exclude selection bias and other confounders, a 1:1 propensity score-based matching procedure was performed resulting in a total number of 238 donors and recipients who were well matched for baseline characteristics. The primary end-points were overall survival after LTx and freedom from bronchiolitis obliterans syndrome (BOS). Secondary end-points were perioperative clinical characteristics as well as adverse events that occurred over the follow-up.
After propensity score matching all donor characteristics and all baseline recipient characteristics were statistically similar between the two groups. In terms of early postoperative results, both groups were statistically comparable. However, there was a trend towards higher incidence of primary graft dysfunction in the external group (P = 0.054). Regarding long-term results with up to 7 years of follow-up, the overall survival also appeared to be poorer in the external group; however, this difference did not reach statistical significance. The freedom from BOS over the long-term follow was significantly poorer in the external group (P = 0.040).
Despite excellent early outcomes the zonal allocation system might be associated with significantly poorer long-term outcomes in terms of freedom from BOS after bilateral LTx. Further research is needed to find the underlying factors leading to these results.