New lesions by themselves may define iUPD (when they appear), or iCPD when they increase in size (5mm or more if they are target, or any increase if non target), or another lesion appears.
However, as noted, the rules of RECIST1.1 always apply – if new lesions appear but then decrease in size or stay stable there are 2 scenarios possible
- each subsequent TP response remains iUPD. Here, any subsequent increase in size of the new lesions (5mm or more* for target or any for non-target new lesions) would allow ICPD to be defined. The TPR would be iUPD, iUPD, iUPD, iCPD for example
- Subsequent TP response is iSD, iPR. Here, the new lesions would result in a new iUPD in the following circumstances
- Further new lesions develop
- The NLT meet RECIST 1.1 criteria for PD (20% or more increase in SOM from ‘baseline’ or nadir)
- The NLNT meet RECIST 1.1 criteria for PD (unequivocal increase equating to a 73% overall increase in tumour burden)
* Note: sequential increases are additive; thus a 4mm increase at one assessment, followed at the next assessment by a further 2mm increase meets the criteria for iCPD.