How would you treat a patient with TNBC with a residual strongly PR+, ER- breast mass on mastectomy after neoadjuvant KEYNOTE 522 based chemoimmunotherapy?

I would treat such a patient the same way that I would any patient with residual TNBC after neoadjuvant chemotherapy and pembrolizumab, which depends to some extent upon the patient's stage at diagnosis and the extent of residual disease at surgery - in patients with residual disease after neoadjuvant chemotherapy for TNBC, patients who were stage III at diagnosis are at greater risk of distant recurrence than those who were stage II (or stage I, if for some reason you decided to administer neoa...

Assuming that the original tissue biopsy was accurate as triple negative tumor, this may be a scenario with heterogenous tumor biology where initial biopsy sampling did not catch PR positivity, and following neoadjuvant therapy PR positive tumor clones remained as dominant residual disease. I would certainly do a NextGen sequencing on the original and/or residual tumor tissue if possible for targetable mutations (BRCA, ESR1, PIK3A, and more).

Outside of a clinical trial, adjuvant pembrolizumab a...