A protocol for the development of core outcome sets for effectiveness trials and clinical audits in renal cell cancer (R-COS)

Background: There is inconsistency in outcomes collected in renal cell cancer (RCC) intervention effectiveness studies and variability in their definitions. This makes critical summaries of the evidence base difficult and sub-optimally informative for clinical practice guidelines and decision-making by patients and healthcare professionals. A solution is to develop a core outcome set (COS), an agreed minimum set of outcomes to be reported in all trials in a clinical area. Objectives: To develop three COS for (a) localised, (b) locally advanced and (c) metastatic RCC study design, participants and methods: The methods are the same for each of our three COS and are structured in two phases. Phase 1 identifies potentially relevant outcomes by conducting both a systematic literature review and patient interviews (N similar to 30 patients). Qualitative data will be analysed using framework analysis. In phase 2, all outcomes identified in phase 1 will be entered in a modified eDelphi, whereby patients and healthcare professionals (50 of each) will score each outcome's importance (Likert scale from 1 [not important] to 9 [critically important]). Outcomes scored in the 7-9 range by =70% and 1-3 by =15% will be regarded as 'consensus in', and the vice versa of this will constitute 'consensus out'. All other combinations will be regarded as equivocal and discussed at consensus meetings (including 10 patients and 10 healthcare professionals) in order to vote on them and ratify the results of the eDelphi. Discussion: The R-COS will reduce outcome reporting heterogeneity and improve the evidence base for RCC. Study registration: The study is registered with the COMET initiative: https://www. comet-initiative.org/studies/details/1406.