Would you add neoadjuvant pembrolizumab to chemotherapy in a premenopausal female with T2N1 breast cancer that is weakly ER or PR positive?

I would not give neoadjuvant pembrolizumab. Although cancers like the one described tend to behave more like triple negative cancers than hormone receptor positive ones, the KEYNOTE-522 study defined triple negative by the ASCO-CAP guidelines which (without knowing the details of this patient's pathology) would have presumably excluded this patient. With that said, I think that there is a possibility that checkpoint inhibitor therapy may be effective in this HR low positive group and trials including these patients are needed. I would also make sure that the PR status is truly accurate and consider re-testing or re-biopsy if indicated, as there could be intra-tumoral heterogeneity.