Minimum exposure and best response definition for primary resistance to immune checkpoint inhibitor−chemotherapy combinations in advanced tumor settings
| Resistance phenotype | Exposure requirement | Timing of RECIST progression* | Confirmatory scan |
| Primary resistance† | 6–8 weeks‡ | ≤6 months | Not required |
| Secondary or late resistance† | >6 months | >6 months | Not required |
*Regardless of best response.
†For patients that experience recurrent disease after stopping therapy for reasons other than toxicity, no uniform clinical definitions of resistance applicable across disease states could be described.
‡For rapidly progressing disease, any exposure is adequate.
RECIST, Response Evaluation Criteria In Solid Tumors.