How do you approach adjuvant treatment of pT1cN0 metaplastic triple negative breast cancer?

Triple negative metaplastic breast cancers (TNMetBC) are rare, relatively chemorefractory tumors that behave quite differently from triple negative ductal cancers. (Reddy et al., PMID 33148288) The two types are usually treated similarly due to a lack of conclusive data on how to optimally treat TNMetBC. Retrospective TNMetBC data suggests anthracyclines did not have much activity and more responses were seen with taxanes. (Chen et al., PMID 21792625). There are some case series data that carbo/taxane treated TNMetBC cases did reasonably well. (Harper et al., PMID 31208874) For these reasons, I would favor adjuvant carbo/taxane doublet over ddAC-T for a stage 1 metaplastic tumor in a 67-year-old.