In RECIST 1.1 the usual principle used is that once a PR has been assigned, and confirmed (if required), then the best response is always PR even is subsequent TP measurements no longer quite meet the criteria (providing that the criteria for PD are not met).  The same principles hold for iRECIST as shown below.

	Baseline	TP1	TP2	TP3	TP4	TP5
T lesions (sum)	100	70	70	80	80	80
NT lesions	Pres	No change	No change	No change	No change	No change
New lesions		–	–	–	–	–
TP response (R)		PR	PR	PR	PR	PR
TP response (iR)		iPR	iPR	iPR	iPR	iPR