Transtuzumab induced organizing pneumonia: a case report

BACKGROUND: Patients with metastatic breast cancer often have pulmonary symptoms with varying aetiologies. Transtuzumab is an extremely important drug used in the treatment of Her 2 neu over-expressing breast cancers. In this report we describe a case of organizing pneumonia associated with use of transtuzumab in metastatic breast cancer. Only three such cases have previously been reported. CASE DESCRIPTION: A 43 year old lady with Her 2 neu 3+, estrogen and progesterone receptor positive, metastatic breast cancer was started on weekly transtuzumab and albumen bound paclitaxel. She was admitted with an episode of bilateral pneumonitis after her fourth dose of therapy. It was managed conservatively with antibiotics. Subsequently, single agent transtuzumab was administered resulting in an anaphylactoid reaction followed by worsening dyspnoea requiring hospitalization and oxygen support for 3 days. DISCUSSION AND EVALUATION: The pneumonitis warranted further investigations including bronchoscopy which were performed. Bronchoscopic biopsy was consistent with a diagnosis of organizing pneumonia. Transtuzumab was stopped and she was started on steroids (dexamethasone). She improved remarkably and was discharged home on hormonal therapy, lapatinib and tapering doses of steroids. CONCLUSION: Organizing pneumonia closely mimics infection or progressive disease and can be difficult to diagnose in the setting of malignancy. Correct diagnosis is of paramount importance since delay in treatment can result in significantly adverse patient outcomes.