MRI guided bx and mentrual cycle

I was originally diagnosed with pleomorphic ILC in 2007. Had a screening breast MRI last month that came back BIRADS 4C--highly suspicious for malignancy. The MRI report states that there is a probable local recurrence at the lumpectomy site with two new suspicious spots in the same breast. The radiologist recommended trying to target the areas via u/s and biopsying that way, then going to MRI guided biopsy if that didn't work.

So I went for the u/s Monday, and they couldn't see anything. The MRI place called today and said I have to wait for my next menstrual cycle to have the MRI guided biopsy done. I've had an MRI guided biopsy done before and did it around my cycle, but that one had been a BIRADS 4A in the "good" breast , not a 4C in the cancer side. When I was first diagnosed in 2007, they did the post-diagnosis breast MRI without regards to my cycle, b/c they said it just needed to get done.

I have a call in to my onc's office to ask if we absolutely have to schedule this biopsy around my cycle. I am irregular and often skip months. Stress doen't help the situation! I realize the MRIs are more accurate between days 7 and 14 of the cycle, but it doesn't seem like we'd be too worried about false positive enhancements at this juncture in my situation.

Just wanted to see if any pre-meno ladies were able to do MRI guided biopsies without regard to where they were in their cycles. Thanks!