A Case of Humidifier Lung Requiring Differentiation from Immune-related Adverse Events during Postoperative Chemotherapy for Breast Cancer

Abstract

A 52-year-old woman with right triple-negative breast cancer, diagnosed with cT2N1M0 Stage IIB disease, was treated with preoperative chemotherapy and surgery, including pembrolizumab, in accordance with the KEYNOTE-522 trial. On the day of the third postoperative course of pembrolizumab, which was scheduled for a total of five courses, the patient complained of fever and cough and showed decreased oxygen saturation. Blood tests, radiography, and computed tomography revealed drug-induced lung disease from pembrolizumab, and the patient was referred to the Respiratory Internal Medicine department on the same day. An interview with a respiratory physician revealed that the patient had started using a humidifier at the start of postoperative adjuvant chemotherapy, and contamination of the humidifier was suspected. The patient was admitted to our hospital for antigen isolation and close examination. At the time of admission, the patient required oxygen administration but quickly improved and was discharged on the 5th day. The patient completed the scheduled adjuvant chemotherapy and is currently under outpatient observation. No symptomatic recurrence was observed.

In this report, we describe a case of a humidifier lung that required a differential diagnosis of drug-induced lung disease due to immune checkpoint drugs.