New biopsy to determine inflammation or refractory Hodgkin's

I was wondering if anyone had to go through this too? My husband has had 4.5 cycles of ABVD and his PET is still positive (SUV of 2.5-3.0, originally 4.5) so the onc and 2 of is colleagues want a new biopsy. They said it is to check if the positive PET is just inflammation or if the cancer has/is becoming refractory. Has anyone else been through this? His onc said even if it is refractory now he is certain he can still "cure" him he just needs to switch chemos for 1-2 cycles. Any help would be appreciated!