HER2 negative but actually a low positive and neratinib

The vast majority of breast cancer drugs start in trials with metastatic patients, where they are studied for a period of time in that population. After noting efficacy, some of these drugs are then extended to the early stage community, where they are studied again - usually more rapidly because the dosing has already been established - and incorporated into the standard of care for early stage. For some of these drugs there are parameters for use such as hormonal receptor arrangement, Her2 status, tumor size/nodal spread, etc. Neratinib is one of those drugs, initially studied and used for metastatic patients, then offered to Her2+ patients who have had chemo and Herceptin, and possibly Perjeta. I have not seen it used for those who are not classified as Her2+, it is not FDA approved for that type of use, nor could I find any trials doing so. It is possible that the I-Spy trials might have been a fit, but I believe that this is for neoadjuvent design so you can't have had surgery yet. Neratinib is currently prescribed to be used after you have completed a year of Herceptin for those who are early stage. I believe the most common side effect is diarrhea, but through experimentation I think they have found that is anti-D meds are taken simultaneously for those with this SE, and/or the dosage is ramped up slowly, it works out - but some have had to discontinue because it can't be controlled.

Enhertu is the big breakthrough drug for HER2 low pts, but I think this is also reserved for metastatic BC at the present time