A recent publication in The Lancet Oncology journal highlights the development, led by the RECIST Working Group, of iRECIST (immunotherapy Response Evaluation Criteria in Solid Tumours) consensus–based guideline, which addresses the novel characteristics of this new class of anticancer therapeutics, ensuring consistent trial design and data collection.

“There are a growing number of new immune modulators being introduced for cancer therapy, and current trials assessing their efficacy are using a variety of response criteria,” said Dr Lesley Seymour, Director of the Investigational New Drug Program, Canadian Cancer Trials Group and lead author on this paper. “The iRECIST guideline, developed by a multidisciplinary group including academic, commercial and regulatory experts, is based on RECIST 1.1 but incorporates additional criteria allowing for consistent interpretation of tumour progression measurements for immunotherapy treatments.”

Novel immunotherapeutics have been shown, in some patients, to trigger different responses in tumours compared to traditional chemotherapy: they may initially increase in size, followed by shrinkage (pseudoprogression). While the RECIST 1.1 guideline may not capture this unusual pattern of response, iRECIST allows for the delayed responses that occur after ‘pseudoprogression’ to be identified and better characterized. The guideline describes a standard approach to solid tumour measurement and definitions for objective change in tumour size which can be used in immunotherapy clinical trials. In addition, it defines the minimum amount of data to be collected in order to create a data warehouse that can be used to later validate iRECIST.