How would you manage subsequent treatment for a patient with metastatic ER+HER2- breast cancer that develops pneumonitis on a CDK4/6 inhibitor but had an excellent response to therapy?  

One of our fellows and I conducted a lit search on this topic several months ago, and then again (briefly) today. There is not much literature to support evidence-based decision making, as the 3 available CDK4/6 inhibitors (palbociclib, abemacicilib, and ribociclib) all have pneumonitis as a reporte...

Decisions like this should always be made with subspecialty input from a pulmonologist, and account for the degree and severity of the pneumonitis. The development of pneumonitis may well be a class effect (indeed, pneumonitis was observed in clinical trials of all three approved CDK4/6 inhibitors) ...