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Would you offer adjuvant TDM-1 to a patient with residual disease after neoadjuvant treatment for biopsy proven HER2 positive breast cancer, although residual tumor biopsy shows discordance with HER2 negative status?
Answer from: Medical Oncologist at Academic Institution
Yes, I would offer T-DM1 in this case since such patients would have been included in the KATHERINE trial that showed a clear benefit in patients with residual invasive disease, unselected for repeat staining (which is not the standard of care) (1). It is plausible that the HER2 status of resi...
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Answer from: Medical Oncologist at Academic Institution
Just curious if this patient is negative by FISH on residual disease? I would treat this patient, irrespective of FISH with TDM-1. In the pivotal trial (von Minckwitz et al., PMID 30516102) of TDM-1 versus trastuzumab, HER2 status was primarily tested on the pretreatment biopsy or if not available, ...
Answer from: Medical Oncologist at Academic Institution
It is not our standard practice to repeat HER2 testing on the surgery specimen. However, this has occurred a few times in my practice. Usually, I would recommend continued treatment for a HER2+ breast cancer. Based on the improved iDFS in KATHERINE, it is standard of care to change to T-DM1...
Answer from: Medical Oncologist at Community Practice
Yes. Trastuzumab and other anti-HER2 neu drugs may have rendered the results from residual tumor falsely negative.