Trial design and endpoints in clinical transplant research

Propensity Score and Instrumental Variable Techniques in Observational Transplantation Studies: An Overview and Worked Example Relating to Pre-Transplant Cardiac Screening

Inferring causality from observational studies is difficult due to inherent differences in patient characteristics between treated and untreated groups. The randomised controlled trial is the gold standard study design as the random allocation of individuals to treatment and control arms should result in an equal distribution of known and unknown prognostic factors at baseline. However, it is not always ethically or practically possible to perform such a study in the field of transplantation. Propensity score and instrumental variable techniques have theoretical advantages over conventional multivariable regression methods and are increasingly being used within observational studies to reduce the risk of confounding bias. An understanding of these techniques is required to critically appraise the literature. We provide an overview of propensity score and instrumental variable techniques for transplant clinicians, describing their principles, assumptions, strengths, and weaknesses. We discuss the different patient populations included in analyses and how to interpret results. We illustrate these points using data from the Access to Transplant and Transplant Outcome Measures study examining the association between pre-transplant cardiac screening in kidney transplant recipients and post-transplant cardiac events.

Demonstrating Benefit-Risk Profiles of Novel Therapeutic Strategies in Kidney Transplantation: Opportunities and Challenges of Real-World Evidence

While great progress has been made in transplantation medicine, long-term graft failure and serious side effects still pose a challenge in kidney transplantation. Effective and safe long-term treatments are needed. Therefore, evidence of the lasting benefit-risk of novel therapies is required. Demonstrating superiority of novel therapies is unlikely via conventional randomized controlled trials, as long-term follow-up in large sample sizes pose statistical and operational challenges. Furthermore, endpoints generally accepted in short-term clinical trials need to be translated to real-world (RW) care settings, enabling robust assessments of novel treatments. Hence, there is an evidence gap that calls for innovative clinical trial designs, with RW evidence (RWE) providing an opportunity to facilitate longitudinal transplant research with timely translation to clinical practice. Nonetheless, the current RWE landscape shows considerable heterogeneity, with few registries capturing detailed data to support the establishment of new endpoints. The main recommendations by leading scientists in the field are increased collaboration between registries for data harmonization and leveraging the development of technology innovations for data sharing under high privacy standards. This will aid the development of clinically meaningful endpoints and data models, enabling future long-term research and ultimately establish optimal long-term outcomes for transplant patients.

The Need to Update Endpoints and Outcome Analysis in the Rapidly Changing Field of Liver Transplantation

Liver transplantation (LT) survival rates have continued to improve over the last decades, mostly due to the reduction of mortality early after transplantation. The advancement is facilitating a liberalization of access to LT, with more patients with higher risk profiles being added to the waiting list. At the same time, the persisting organ shortage fosters strategies to rescue organs of high-risk donors. This is facilitated by novel technologies such as machine perfusion. Owing to these developments, reconsideration of the current and emerging endpoints for the assessment of the efficacy of existing and new therapies is warranted. While conventional early endpoints in LT have focused on the damage induced to the parenchyma, the fate of the bile duct and the recurrence of the underlying disease have a stronger impact on the long-term outcome. In light of this evolving landscape, we here attempt to reflect on the appropriateness of the currently used endpoints in the field of LT trials.

Does renal transplant in children with LUTD improve their bladder function?

Much is still unknown about LUT function after receiving renal graft. Graft function was the main focus of different studies discussing the same issue. However, these studies ignored the effects of the graft on lower tract function and more demand for bladder cycling and growth of the child. Therefore, we aimed at evaluating the LUT function after RT into patients with LUTD. We enrolled a retrospective cohort of 83 live renal transplant children with LUTD. The 44 patients in Group (A) had a defunctionalized bladder, and the 39 patients in Group (B) had underlying LUT pathology. All patients had clinical and urodynamic evaluation of LUT functions at least 1 year after RT. We found that the improvement in patients with impaired bladder compliance was 73% in Group (A) and 60% in Group (B), with no statistically significant difference between the study groups. In Group (B), there was statistically significant worsening of MFP (8.4%) and mean PVR (79.9%) after RT. In Group (A), mild but stable significant improvement of all clinical and urodynamic parameters was observed. Serum creatinine was significantly worse in patients with pathological LUTD compared with those with defunctionalized bladder but without significant effect on graft survival. All LUT variables seemed to have no adverse effect on graft survival except for use of CIC and augmented bladder. Incident UTI independent of LUT variables accounted for 20% of graft creatinine change.

Prognostic value for long-term graft survival of estimated glomerular filtration rate and proteinuria quantified at 3 months after kidney transplantation

Background

The estimated glomerular filtration rate (eGFR) measured at 1 year is the usual benchmark applied in kidney transplantation (KT). However, acting on earlier eGFR values could help in managing KT during the first post-operative year. We aimed to assess the prognostic value for long-term graft survival of the early (3 months) quantification of eGFR and proteinuria following KT.

Methods

The 3-, 6- and 12-month eGFR using the Modified Diet in Renal Disease equation (eGFR_MDRD) was determined and proteinuria was measured in 754 patients who underwent their first KT between 2000 and 2010 (with a mean follow-up of 8.3 years) in our centre. Adjusted associations with graft survival were estimated using a multivariable Cox model. The predictive accuracy was estimated using the C-index and net reclassification index. These same analyses were measured in a multicentre validation cohort of 1936 patients.

Results

Both 3-month eGFR_MDRD and proteinuria were independent predictors of return to dialysis (all P < 0.05) and there was a strong correlation between eGFR at 3 and 12 months (Spearman’s ρ = 0.76). The predictive accuracy of the 3-month eGFR was within a similar range and did not differ significantly from the 12-month eGFR in either the derivation cohort [C-index 62.6 (range 57.2–68.1) versus 66.0 (range 60.1–71.9), P = 0.41] or the validation cohort [C-index 69.3 (range 66.4–72.1) versus 71.7 (range 68.7–74.6), P = 0.25].

Conclusion

The 3-month eGFR was a valuable predictor of the long-term return to dialysis whose predictive accuracy was not significantly less than that of the 12-month eGFR in multicentre cohorts totalling >2500 patients. Three-month outcomes may be useful in randomized controlled trials targeting early therapeutic interventions.

Preservation of kidney function in kidney transplant recipients by alkali therapy (Preserve-Transplant Study): rationale and study protocol

Background

Graft survival after kidney transplantation has significantly improved within the last decades but there is a substantial number of patients with declining transplant function and graft loss. Over the past years several studies have shown that metabolic acidosis plays an important role in the progression of Chronic Kidney Disease (CKD) and that alkalinizing therapies significantly delayed progression of CKD. Importantly, metabolic acidosis is highly prevalent in renal transplant patients and a recent retrospective study has shown that metabolic acidosis is associated with increased risk of graft loss and patient death in kidney transplant recipients. However, no prospective trial has been initiated yet to test the role of alkali treatment on renal allograft function.

Methods

The Preserve-Transplant Study is an investigator-initiated, prospective, patient-blinded, multi-center, randomized, controlled phase-IV trial with two parallel-groups comparing sodium bicarbonate to placebo. The primary objective is to test if alkali treatment will preserve kidney graft function and diminish the progression of CKD in renal transplant patients by assesing the change in eGFR over 2 years from baseline. Additionally we want to investigate the underlying pathomechanisms of nephrotoxicity of metabolic acidosis.

Discussion

This study has the potential to provide evidence that alkali treatment may slow or reduce the progression towards graft failure and significantly decrease the rate of end stage renal disease (ESRD), thus prolonging long-term graft survival. The implementation of alkali therapy into the drug regimen of kidney transplant recipients would have a favorable risk-benefit ratio since alkali supplements are routinely used in CKD patients and represent a well-tolerated, safe and cost-effective treatment.

Trial registration

ClinicalTrials.gov NCT03102996. Trial registration was completed on April 6, 2017.

Clinicians' and researchers' perspectives on establishing and implementing core outcomes in haemodialysis: semistructured interview study

OBJECTIVES

To describe the perspectives of clinicians and researchers on identifying, establishing and implementing core outcomes in haemodialysis and their expected impact.

DESIGN

Face-to-face, semistructured interviews; thematic analysis.

STETTING

Twenty-seven centres across nine countries.

PARTICIPANTS

Fifty-eight nephrologists (42 (72%) who were also triallists).

RESULTS

We identified six themes: reflecting direct patient relevance and impact (survival as the primary goal of dialysis, enabling well-being and functioning, severe consequences of comorbidities and complications, indicators of treatment success, universal relevance, stakeholder consensus); amenable and responsive to interventions (realistic and possible to intervene on, differentiating between treatments); reflective of economic burden on healthcare; feasibility of implementation (clarity and consistency in definition, easily measurable, requiring minimal resources, creating a cultural shift, aversion to intensifying bureaucracy, allowing justifiable exceptions); authoritative inducement and directive (endorsement for legitimacy, necessity of buy-in from dialysis providers, incentivising uptake); instituting patient-centredness (explicitly addressing patient-important outcomes, reciprocating trial participation, improving comparability of interventions for decision-making, driving quality improvement and compelling a focus on quality of life).

CONCLUSIONS

Nephrologists emphasised that core outcomes should be relevant to patients, amenable to change, feasible to implement and supported by stakeholder organisations. They expected core outcomes would improve patient-centred care and outcomes.

Standardized Duplex Ultrasound-Based Protocol for Early Diagnosis of Transplant Renal Artery Stenosis: Results of a Single-Institution Retrospective Cohort Study

Transplant renal artery stenosis (TRAS) is the most frequent vascular complication after kidney transplantation (KT) and has been associated with potentially reversible refractory hypertension, graft dysfunction, and reduced patient survival. The aim of the study is to describe the outcomes of a standardized Duplex Ultrasound- (DU-) based screening protocol for early diagnosis of TRAS and for selection of patients potentially requiring endovascular intervention. We retrospectively reviewed our prospectively collected database of KT from January 1998 to select patients diagnosed with TRAS. The follow-up protocol was based on a risk-adapted, dynamic subdivision of eligible KT patients in different risk categories (RC) with different protocol strategies (PS). Of 598 patients included in the study, 52 (9%) patients had hemodynamically significant TRAS and underwent percutaneous angioplasty (PTA) and stent placement. Technical and clinical success rates were 97% and 90%, respectively. 7 cases of restenosis were recorded at follow-up and treated with re-PTA plus stenting. Both DU imaging and clinical parameters improved after stent placement. Prospective high-quality studies are needed to test the efficacy and safety of our protocol in larger series. Accurate trial design and standardized reporting of patient outcomes will be key to address the current clinical needs.

The New Era of Transplant Oncology: Liver Transplantation for Nonresectable Colorectal Cancer Liver Metastases

Colorectal cancer (CRC) is the third most incident cancer worldwide. Most of CRC patients will develop distant metastases, mainly to the liver, and liver resection is the only potential chance for cure. On the other hand, only a small proportion of patients with hepatic CRC metastasis are candidates for upfront liver resection. Liver transplantation (LT) is an attractive option for patients with nonresectable CRC liver metastases (NRCLM) without extrahepatic involvement. Initial experiences with LT for NRCLM achieved very poor outcomes, with a 5-year overall survival (OS) lower than 20%. However, these initial studies did not have a standardized patient selection or neoadjuvant or adjuvant therapies. With recent advances in the surgical and medical oncology fields, the landscape has changed. Recent studies from Norway have shown an encouraging 5-year OS of 50% when transplanting patients with NRCLM. Nevertheless, the main concern when expanding the indications for LT is organ shortage. To manage this organ shortage, strategies utilizing live donor liver transplantation are gaining favor. A few ongoing trials are assessing the impact of LT in NRCLM patient survival. Therefore, the aim of this paper is to review the current status of LT for NRCLM.

Toward Establishing Core Outcome Domains For Trials in Kidney Transplantation: Report of the Standardized Outcomes in Nephrology-Kidney Transplantation Consensus Workshops

BACKGROUND

Treatment decisions in kidney transplantation requires patients and clinicians to weigh the benefits and harms of a broad range of medical and surgical interventions, but the heterogeneity and lack of patient-relevant outcomes across trials in transplantation makes these trade-offs uncertain, thus, the need for a core outcome set that reflects stakeholder priorities.

METHODS

We convened 2 international Standardized Outcomes in Nephrology-Kidney Transplantation stakeholder consensus workshops in Boston (17 patients/caregivers; 52 health professionals) and Hong Kong (10 patients/caregivers; 45 health professionals). In facilitated breakout groups, participants discussed the development and implementation of core outcome domains for trials in kidney transplantation.

RESULTS

Seven themes were identified. Reinforcing the paramount importance of graft outcomes encompassed the prevailing dread of dialysis, distilling the meaning of graft function, and acknowledging the terrifying and ambiguous terminology of rejection. Reflecting critical trade-offs between graft health and medical comorbidities was fundamental. Contextualizing mortality explained discrepancies in the prioritization of death among stakeholders-inevitability of death (patients), preventing premature death (clinicians), and ensuring safety (regulators). Imperative to capture patient-reported outcomes was driven by making explicit patient priorities, fulfilling regulatory requirements, and addressing life participation. Specificity to transplant; feasibility and pragmatism (long-term impacts and responsiveness to interventions); and recognizing gradients of severity within outcome domains were raised as considerations.

CONCLUSIONS

Stakeholders support the inclusion of graft health, mortality, cardiovascular disease, infection, cancer, and patient-reported outcomes (ie, life participation) in a core outcomes set. Addressing ambiguous terminology and feasibility is needed in establishing these core outcome domains for trials in kidney transplantation.

Clinical Evaluation of Modified Release and Immediate Release Tacrolimus Formulations

The science of drug delivery has evolved considerably and has led to the development of multiple sustained release formulations. Each of these formulations can present particular challenges in terms of clinical evaluation and necessitate careful study to identify their optimal use in practice. Tacrolimus is an immunosuppressive agent that is widely used in organ transplant recipients. However, it is poorly soluble, has an unpredictable pharmacokinetic profile subject to important genetic polymorphisms and drug-drug interactions, and has a narrow therapeutic index. For these reasons, it represents an agent that could benefit from modified release formulations to overcome these limitations. The objective of this review is to discuss the clinical evaluation of immediate and modified release tacrolimus formulations in renal transplant recipients. Clinical trials from early development of immediate release tacrolimus to formulation-specific post-marketing trials of modified release tacrolimus formulations are reviewed with an emphasis on key elements relating to trial design end endpoint assessment. Particular elements that can be addressed with formulation alterations, such as pharmacokinetics, pharmacogenomics, and toxicity and corresponding clinical evaluations are discussed. In addition, current knowledge gaps in the clinical evaluation of immediate and modified release tacrolimus formulations are discussed to highlight potential avenues for the future development of different tacrolimus formulations with outcomes relevant to the regulators, the transplant community, and to transplant recipients. This review shows that new formulations may alter tacrolimus bioavailability, alleviate certain adverse events while potentially enhancing patient convenience.

Research priority setting in organ transplantation: a systematic review

Barriers to access and long-term complications remain a challenge in transplantation. Further advancements may be achieved through research priority setting with patient engagement to strengthen its relevance. We evaluated research priority setting in solid organ transplantation and described stakeholder priorities. Databases were searched to October 2016. We synthesized the findings descriptively. The 28 studies (n = 2071 participants) addressed kidney [9 (32%)], heart [7 (25%)], liver [3 (11%)], lung [1 (4%)], pancreas [1 (4%)], and nonspecified organ transplantation [7 (25%)] using consensus conferences, expert panel meetings, workshops, surveys, focus groups, interviews, and the Delphi technique. Nine (32%) reported patient involvement. The 336 research priorities addressed the following: organ donation [43 priorities (14 studies)]; waitlisting and allocation [43 (10 studies)]; histocompatibility and immunology [31 (8 studies)]; immunosuppression [21 (10 studies)]; graft-related complications [38 (13 studies)]; recipient (non-graft-related) complications [86 (14 studies)]; reproduction [14 (1 study)], psychosocial and lifestyle [49 (7 studies)]; and disparities in access and outcomes [10 (4 studies)]. The priorities identified were broad but only one-third of initiatives engaged patients/caregivers, and details of the process were lacking. Setting research priorities in an explicit manner with patient involvement can guide investment toward the shared priorities of patients and health professionals.

Quality and consistency of outcome reporting in clinical trials of immunosuppression in renal transplantation

Interpretation, comparison, and combination of results of clinical trials are reliant on accurate and complete reporting of outcomes. This study aimed to assess the quality and variability in outcome reporting in immunosuppression trials following renal transplantation. All randomized controlled trials comparing immunosuppressive interventions in renal transplant recipients published over a 5-year period were included. Outcomes reported in these studies were extracted, along with data regarding completeness of reporting and whether a clear definition of the method used to measure the outcome was provided. A total of 4760 outcomes were identified from 182 studies. Overall, 90.3% outcomes were completely reported; the remainder had missing data that would preclude use in meta-analysis; 31.5% manuscripts did not define a primary endpoint. Efficacy outcomes were more likely to be clearly defined than safety outcomes (OR: 0.022, P<.001) or patient-reported outcome measures (PROMs) (OR: 0.014, P<.001). PROMs were reported in less than half of manuscripts, and only five reported quality-of-life data using a validated tool. There was significant variability in the way that common efficacy and safety outcomes were defined. Variability in the way that endpoints are selected and reported in trials in renal transplantation makes interpretation and comparison between studies difficult.

Standardized Outcomes in Nephrology-Transplantation: A Global Initiative to Develop a Core Outcome Set for Trials in Kidney Transplantation

Background

Although advances in treatment have dramatically improved short-term graft survival and acute rejection in kidney transplant recipients, long-term graft outcomes have not substantially improved. Transplant recipients also have a considerably increased risk of cancer, cardiovascular disease, diabetes, and infection, which all contribute to appreciable morbidity and premature mortality. Many trials in kidney transplantation are short-term, frequently use unvalidated surrogate endpoints, outcomes of uncertain relevance to patients and clinicians, and do not consistently measure and report key outcomes like death, graft loss, graft function, and adverse effects of therapy. This diminishes the value of trials in supporting treatment decisions that require individual-level multiple tradeoffs between graft survival and the risk of side effects, adverse events, and mortality. The Standardized Outcomes in Nephrology-Transplantation initiative aims to develop a core outcome set for trials in kidney transplantation that is based on the shared priorities of all stakeholders.

Methods

This will include a systematic review to identify outcomes reported in randomized trials, a Delphi survey with an international multistakeholder panel (patients, caregivers, clinicians, researchers, policy makers, members from industry) to develop a consensus-based prioritized list of outcome domains and a consensus workshop to review and finalize the core outcome set for trials in kidney transplantation.

Conclusions

Developing and implementing a core outcome set to be reported, at a minimum, in all kidney transplantation trials will improve the transparency, quality, and relevance of research; to enable kidney transplant recipients and their clinicians to make better-informed treatment decisions for improved patient outcomes.