Problems of Utility With Organ Allocation to Multi-organ Transplant Recipients
This variation in MOT practice and the absence of minimal listing criteria create the possibility of inefficient organ allocation (as measured by survival benefit derived from the organs), while making it difficult for practitioners to interpret outcome data and construct valid risk-benefit assessments of MOT for most patients. The lack of minimal listing criteria for MOT enables physicians to list some patients for MOT whose outcome may only be improved incrementally by the nonprimary organ—and diverts that nonprimary organ from other candidates who may die waiting. For example, it is common for MOT candidates to receive a kidney transplant even before receiving chronic dialysis, because of the concern that complications of transplant surgery may cause the patient's chronic kidney disease to proceed to ESRD. However, unlike candidates for a kidney-alone transplant who must demonstrate an estimated glomerular filtration rate (eGFR) ≤20 mL/min/1.73 m, a MOT candidate does not need to demonstrate any level of eGFR to obtain a kidney.
Unfortunately, the lack of high-quality data about the added value of MOT versus single-organ transplant has undermined consensus about what should constitute minimal clinical criteria. No randomized controlled trials of single-organ transplant versus MOT have been conducted. Most studies have been retrospective and commonly based on data from the Organ Procurement and Transplantation Network (OPTN), with the prominent limitation of unmeasured confounding, because MOT candidates differ in meaningful ways from single-organ recipients. The other valuable data source has been single-center studies with the problem of limited generalizability. In the case of SLK, for example, an analysis of OPTN data by Locke et al suggested that due to an elevated risk of ESRD after liver transplant alone, SLK should be considered for liver transplant candidates with >12 weeks of dialysis. An analysis by Ruebner et al of nondialyzed liver transplant candidates suggested that diabetic patients with a median eGFR <30 mL/min/1.73 m should also be considered for SLK. When the cause of renal dysfunction is established as hepatorenal syndrome, which is often reversible after successful liver transplantation, SLK is unlikely to improve outcomes. However, perhaps due to limitations of the available data, two consensus conferences on the selection of patients for SLK recommended very different clinical criteria for candidates.
Wolf et al recently reported lower survival on the waiting list and after transplant for simultaneous thoracic and abdominal (STA) transplantation candidates versus single-organ candidates. Using registry data, Wolf et al found that posttransplant survival was worse than the reference group of abdominal transplant recipients at 1 and 5 years for all STA combinations except simultaneous heart–liver recipients. STA recipients' outcomes were similar to thoracic-only recipients. The authors suggest that data are needed to support utility claims that distribution of more than one organ to one individual leads to "long-term viability of the allocated resource(s)."
Given the limitations of observational studies, decision analysis may offer a complementary approach to estimating utility from MOT. For example, Kiberd et al examined whether greater net patient survival would result from separate allocation of a liver and kidney to two transplant candidates versus SLK to a single candidate. Separate allocation led to greater total quality adjusted life years unless the SLK recipient had a very high probability of ESRD by 1-year posttransplant. A similar approach could be useful in comparing net outcomes in allocation if SPK candidates were provided with various levels of priority for the kidney versus kidney-alone candidates.