@cookercooker
I am in a clinical trial and the two drugs are letrozole and verzenio (abimacyclib). They feel that my tumor was estrogen based so they gave me two breast cancer drugs and the tumor went away for the 2nd time. I did not have any issues with letrozole but the verzenio affected my kidneys (GFR). We now think it might be affecting the prednisone which is trying to get rid of the organizing pneumonia. I have had the pneumonia for 16 months & I believe I it got from the immunotherapy drug keytruda (pembrolizumab).
I hope this information is helpful to you.