When does dr do tests to check...

I do not know what the standard of care is regarding scans to see if the chemo is working, but were it me I'd be asking that question every week. It seems important to me and to you too, obviously. As my aunt used to tell me "you have cancer, you're entitled to ask anything at any time". Don't be shy.

Here, if you've had surgery already and are doing chemo after, they don't do scans. The surgery took all the visible cancer if they got good margins. Chemo is to stop seeding of little tiny cells which wouldn't show on a scan anyway.

I think additional scans are more common if they're doing chemo before surgery to shrink a tumor prior to surgical removal.

I had an MRI after neoadjuvant chemo. We discussed doing it part way through chemo when I was considering quitting, but ... sometimes what is "seen" on scans isn't really true. For instance - sometimes the cancer kind of does a Swiss cheese thing which is hard to evaluate on a scan.

Final surgical pathology is the most helpful. That should guide any follow up care.