What is a ‘Core Outcome Set’?

In this article, we will set out some basic definitions for the work we will be developing over the coming months and years.

What is a ‘Core Outcome Set’?

The GASTROS study aims to develop a core outcome set for trials examining surgical treatments for gastric cancer. A ‘core outcome set’ is defined as a standardized collection of outcomes that all trials looking at a specific clinical area report as a minimum.  It is a recommendation of ‘what’ should be measured. Ensuring that all trials report the same outcomes means that more meaningful comparisons can be made between studies. This is especially so in conditions such as gastric cancer where the overall survival remains poor and so reliably identifying effective treatments is vital.

What is an ‘Outcome Measurement Instrument’?

Outcome measurement instruments are tools to enable to measurement of outcomes. It is a recommendation of ‘how’ the chosen outcome should be reported. GASTROS aims to identify the most appropriate outcome measurement instruments to accompany the core outcome set. By doing so, it will enable more consistent reporting of outcomes in trials.

Worked Examples

An example of an outcome (‘what’ should be measured) is ‘survival following treatment’. This outcome may be measured in different ways (‘how’ – outcome measurement instrument); 30, 60 and 90-days or 1, 3 and 5 year survival. Survival may be defined as ‘overall survival’ or ‘disease-free survival’. The task of the GASTROS study is to determine whether ‘survival’ should be in the core outcome set, the most appropriate instrument to measure ‘survival’ and agree definitions through consultation with key stakeholders.

Another example of an outcome is ‘complications following treatment’.  How complications are measured (e.g. types of complications, severity of complications and the timing of complications) will be within the remit of our study.