In which patients do you utilize a breast MRI as part of the initial workup for breast cancer?

I'm not a fan of routine MRI in the work-up for early-stage breast cancer, but I do agree with the fairly standard list of selective indications mentioned previously.

I also obtain an MRI when there is a significant discrepancy between standard imaging and physical exam. Examples would be:

1. One or a few small lesions on mammogram/US, but a large palpable lesion on exam,
2. An unexpected palpable lesion distinct from what was reported,
3. A palpable lesion much larger than characterized by standard diagnostic images.

I think personally reviewing images rather than relying on reports, and particularly careful physical examination to correlate with imaging, is an oncology "super power." :)

Usually, for us, it is done for lobular pathology, locally advanced breast cancer, or dense breast tissue.

We recently endorsed and expanded upon the Cancer Care Ontario (CCO) list of indications for pre-operative breast MRI in a modified Delphi consensus of expert opinion Cao et al., PMID 39590163

Preoperative breast MRI was recommended in the following situations:

• In patients diagnosed with invasive lobular carcinoma for whom additional information about disease extent could influence treatment
• To aid in surgical planning for breast-conserving surgery in patients with suspected or known multicentric or multifocal disease
• To identify additional lesions in patients with dense breasts
• To determine the presence of pectoralis major muscle/chest wall invasion in patients with posteriorly located tumours or when invasion is suspected
• To aid in surgica...

MRI discovers a second focus in 15-30% of patients. I try to use MRI often in my patients to aid in surgical and radiation treatment planning. At least 50% of the lesions detected are biopsy positive.