I think it depends on the patient and how they are responding. I know they told us PET CT scans after the 3rd or 4th treatment and then again 2 months after completion. Because we've had so many chemo related hospitalizations and complications we've already had 2 PET CT scans and a few MRIs and we've only had 3 treatments. On our case it worked out as the first scan didn't show much progress, but the second one showed significant progress. It's nice to know halfway through it all these chemicals are worth it.

I thought after each 4 rounds of infusions was PET scan time. Just found out from my oncologist, they do it every 3 months.

I had PET Scabs every 3 months