Would you drop carboplatin/paclitaxel weeks or considering shortening duration of treatment in a BRCA1+ patient with synchronous TNBC (left 2.4 cm tumor, right 9 mm tumor) who has complete response on interim breast ultrasound?

From a medical oncology perspective, the short answer would be no. The ability of imaging to predict pathologic complete response is not good enough. For example, here is one looking at MRI: Weber et al., PMID 28919579. Imaging isn't good enough to spot a true path CR. Certainly, if there is toxicity you can consider what to do with therapy, but shortening it because you "think" you're there I think would be unadvisable. If you had residual disease on path and you had short changed the therapy, ...