Revised European guidelines on measuring tumour size and response to treatment should ease workloads in clinical trials for cancer without compromising outcomes, the authors say.

The first formal revision of the RECIST (Response Evaluation Criteria in Solid Tumours) guidelines has been published in a special issue of the European Journal of Cancer (EJC), the official publication of the European CanCer Organisation (ECCO). First published in 2000, the guidelines are used by investigators in Phase II and Phase III clinical trials of new cancer drugs as a way of measuring treatment efficacy.

Tumour shrinkage (objective response) and time to development of disease progression are important endpoints in oncology trials, ECCO points out. In recent years there has been a growing trend towards use of time to progression, or progression-free survival, as the main endpoint on which to base conclusions about drug efficacy.

According to ECCO, the new RECIST guidelines – or RECIST 1.1 – “answer some of the questions and issues that have arisen since 2000 as a result of changing methodologies and available treatments” in oncology.

RECIST 1.1 describes a standard approach to solid-tumour measurement and provides definitions for objective assessment of change in tumour size in adult clinical trials, notes Professor Jaap Verweij, clinical oncology editor for the EJC.

“Drug development and clinical cancer research is a global enterprise,” points out co-editor Professor Elizabeth Eisenhauer. “The more consistent we are in describing what we have seen, and in using the same measures and endpoints, the more reliably we are able to interpret the results from a variety of sources.”

The key changes in RECIST 1.1 that ECCO says will “simplify, optimise and standardise” the assessment of tumour burden in clinical trials are:

- A reduction in the number of lesions to be assessed for response from a maximum of ten to five, and from five to a maximum of two per organ.
- New guidance on making robust measurements of lymph node involvement.

- Confirmation of response is required for trials with objective response as a primary endpoint but no longer for randomised studies, since the control arm of these studies provides an appropriate means of interpreting results in the experimental arm.
- The definition of disease progression has been refined so that it includes not only a 20% increase in the size of the lesion but also a 5mm absolute increase. This means changes of just a few millimetres in very small tumours, which may be within the range of measurement error, will not be unnecessarily described as disease progression.
- Guidance on imaging, including its use in the detection of new lesions and the interpretation of FDG-PET (fluorodeoxyglucose-positron emission tomography) scan assessment.