How do you approach adjuvant chemotherapy in early stage ER+ breast cancer who developed pneumonitis on ddAC?  

Neulasta with ddAC  can cause an interstitial pneumonia or reaction like pneumonitis. If she was node positive, younger and you think rechallenging her is reasonable (the pneumonitis was grade 1-2 and resolved quickly on steroids) then you could try to do the remaining AC q3wk without Neulasta ...

Generally agree. Would consider re-challenge with AC without neulasta only if the pneumonitis was mild and resolved. If more moderate to severe, would move on to weekly paclitaxel.

I would have to be convinced that the potential benefit of administering an anthracycline over alternatives like TC was large enough to justify the risk - such as triple negative with positive nodes or ER+/HER2- with at least 4 positive nodes. In that case, one option to consider would be sequential...

Agree with the team.  Considering the patient’s age and presence of high risk features, TC is an option as well as a 3 week cycle. CBC should be carefully monitored given the risks of febrile neutropenia.