European Journal of Cancer
Volume 45, Issue 2, January 2009
The only proven way of measuring tumour response is by measuring size on imaging. This of course is subject to measurement error, and so criteria have been published that allow measurement of response in even small tumours (5mm)
When it comes to clinical trials of therapeutic agents, tumour shrinkage (objective response) and time to the development of disease progression are both important endpoints in trials, and, increasingly in recent years, trials have been using time to progression (or progression-free survival) as their main endpoint on which to base conclusions about the efficacy of a drug.
The new RECIST (RECIST 1.1 to distinguish them from the original RECIST) answer some of the questions and issues that have arisen since 2000 as a result of changing methodologies and available treatments
Key changes in RECIST 1.1 that will simplify, optimise and standardise the assessment of tumour burden in clinical trials are as follows:
- 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 is no longer required for randomised studies, since the control arm of these studies provides appropriate means for interpreting results of the experimental arm
- The definition of disease progression has been refined so that it not only includes a 20% increase in the size of the lesion, but also a 5 mm absolute increase as well, so that changes of just a few mms in very small tumours, which may be within the range of measurement error, are not unnecessarily described as disease progression
- Guidance on imaging, including its use in the detection of new lesions and the interpretation of FDG-PET scan assessment
