A systematic review of heterogeneity in outcome definition and reporting in localised renal cancer

Context: Outcomes in renal cell carcinoma (RCC) are reported inconsistently with variability in definition and measurement. Hence, it is difficult to compare intervention effectiveness and synthesise outcomes for systematic reviews or create clinical practice guidelines. This uncertainty in the evidence makes it difficult to guide patient-clinician decision-making. One solution is a core outcome set (COS): an agreed minimum set of outcomes.
Objective: We aimed to describe outcome reporting, definitions, and measurement heterogeneity as the first stage of co-creating a COS for localised renal cancer.
Evidence Acquisition: We systematically reviewed outcome reporting heterogeneity in localised RCC effectiveness trials and observational studies. In total, 2822 studies (randomized controlled trials, cohort studies, case control studies, systematic reviews) up to June 2020 met our inclusion criteria were identified. Abstracts and full texts were screened independently by two reviewers and in the case of disagreement, a third reviewer arbitrated. Data extractions were double-checked.
Evidence Synthesis: We included 149 studies and found that there were inconsistency in which outcomes were reported across studies and variability in the definitions used for outcomes which were conceptually the same We structured our analysis using the outcome classification taxonomy proposed by Dodd et al. Outcomes linked to adverse events (e.g., bleeding, outcomes linked to surgery) and renal injury outcomes (reduced renal function) were reported most commonly. Outcomes related to deaths due to any cause and due to
cancer were reported in 44% and 25% of studies respectively though the time point of measurement and analysis methods were inconsistent. Outcomes linked to life impact (e.g., global quality of life) were reported least often. Clinician reported outcomes are more frequently reported than patient reported outcomes in the renal cancer literature.
Conclusion: This systematic review underscores the heterogeneity of outcome reporting, definition, and measurement in localised renal cancer research. It catalogues the variety of outcomes and serves as first step towards the development of a core outcome set for localised renal cancer.
Patient Summary: Multiple terms and definitions to describe outcomes linked to localised renal cancer are used in the evidence. These are not defined consistently, and often not defined at all. This is the first phase of developing a core outcome set to enable better comparison to improve medical care.
Take Home Message: Our review indicates that clinical research for localised renal cancer is impeded by heterogeneity in outcome selection, definitions, and reporting. This work forms the first step in the development of a COS to improve the process for making clinical practice guidelines and facilitate healthcare professional and patient treatment decision making.