That has spread to other parts of the body - meaning it's metastatic - as the first hormonal based therapy. ibrance plus letrozole significantly delayed disease progression versus letrozole. patients taking ibrance can develop low white blood cell counts which may cause serious infections that can lead to death. before taking ibrance, tell your doctor if you have fever, chills, or other signs of infection, liver or kidney problems, are pregnant, breastfeeding, or plan to become pregnant. common side effects include low red blood cell and low platelet counts, infections, tiredness, nausea, sore...