Clinical Research: Phase 1 - Phase 4

Considering iRECIST Guidance in Evaluating Solid Tumors

In evaluating patient response to treatment of solid tumors, the nearly decade-old RECIST 1.1 guideline remains the gold standard. But the implementation earlier this year of the iRECIST guidance is focusing attention on how the many wide-ranging approaches to tumor assessment interrelate, and how they rank in relevance — today and looking forward.

It all started in 2000, when the Response Evaluation Criteria In Solid Tumors working group published a set of rules to define when tumors in cancer patients improved (or “responded,” in RECIST terminology), stayed the same (“stabilized”), or worsened (“progressed,” in RECIST lingo.) The criteria were published in February 2000 and supplanted in 2008 with the issuance of the updated RECIST 1.1.

Other criteria emerged in the meantime:

  • irRC, the Immune-Related Response Criteria, a bidimensional tumor measurement standard that’s now rarely used.
  • irRECIST, a unidimensional measurement technique that has demonstrated reduced variability and, alongside RECIST 1.1, remains a prominent method for evaluating treatment response.

Enter the iRECIST guidelines, published in early 2017 to promote standardization and validation of immune response criteria. It’s a unidimensional approach that defines measures for tumor progression and is expected to be the most commonly used standard in future clinical trials.

We stress future, however. While industry, academia, and regulators are embracing iRECIST, it is not today considered appropriate as guidance for treatment decisions. In late-phase and approval trials, RECIST 1.1 remains the primary criteria, with iRECIST seen as having high exploratory value. In early-phase studies, however, iRECIST is considered a suitable source of primary criteria in cases when assessment is performed via RECIST 1.1.

We covered immune-related treatment response in detail in our Expanding the Potential of Immuno-Oncology Therapies webinar, which you can watch online.