Interstitial Pneumonitis Secondary to Trastuzumab: A Case Report and Literature Review.

Interstitial lung disease is a rare complication of trastuzumab-based breast cancer treatment with few case reports published. Herein, we report the case of a 67-year-old female with early-stage HER2-postitive breast cancer who developed interstitial pneumonitis during cycle 5 of treatment with trastuzumab combined with carboplatin and docetaxel. After supportive care and treatment with prednisone, the patient showed rapid improvement of respiratory symptoms. Retreatment with trastuzumab as a single agent led to worsening of symptoms and required a second course of treatment with prednisone combined with cyclophosphamide, which was followed by improvement of symptoms. In conclusion, interstitial pneumonitis is a rare but life-threatening adverse event from trastuzumab breast cancer treatment.