immune-related response criteria (irRC) replace RECIST for ICI treatments

[Olga]

Immune-related response evaluations during immune-checkpoint inhibitor therapy: establishing a “common language” for the new arena of cancer treatment
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4915158/
Response patterns unique to immune-checkpoint inhibitor therapy can be noted i) after an initial increase of tumor burden or ii) during or after the appearance of new lesions [5–7]. The phenomena are termed “pseudoprogression”, because they would be classified as progressive disease (PD) by conventional RECIST [5–9]. To capture these unconventional response patterns, irRC was proposed in 2009 with the key features including 1) requirement of confirmation of PD on two consecutive scans at least 4 weeks apart, and 2) inclusion of new lesion measurements to the total tumor burden [5–7]. These criteria are distinct from RECIST which immediately defines PD at tumor burden increase above the threshold or at the appearance of new lesions. While irRC is increasingly recognized, most trials of immune-checkpoint inhibitors continue to use RECIST1.1 to obtain standardized endpoints used for regulatory approvals in the past decade. Moreover, regulatory authorities have not yet accepted immune-related response evaluations as an endpoint for registrational studies