Assigning response after the appearance of new lesion/s: must the new lesion/s resolve completely before an iPR or iCR can be assigned?

A number of questions have been received regarding the impact of new lesions on subsequent i-response assignment. The key principle is that the ‘new lesion’ may have resulted from immune infiltration rather than tumour growth. Therefore the continued presence of a ‘new lesion’, providing it does not increase further in size (using the 5mm rule), does not preclude subsequent cycles being assigned iSD, iPR or iCR*. This is demonstrated in supplementary materials.

  • In scenario B
  • In scenario D, there is iUPD after PR/iPR, with a 20% increase in target SOM, plus a new lesion; at the next assessment the target lesion SOM no longer meets the criteria for PD and has shrunk sufficiently to qualify for iPR (from baseline) and the new lesion disappears – note that this would be iPR even if the new lesion remained visible as long as not had not increased (by 5mm or more for target NLs or any increase if non target).
  • In scenario F, PR/iPR criteria are met at TP1, but at TP2 a new lesion develops, which remains unchanged at the next assessment. TP3 therefore remains iUPD as iCPD cannot be confirmed; it is not iPR as no further change in target SOM has occurred from TP1.

* Note: ideally iCR should not be assigned until the residual new lesion has been confirmed to be non-malignant pathologically or with functional imaging.