Incidence of interstitial lung disease in patients with breast cancer: a nationwide database study in Japan.

This study estimated the incidence of moderate-to-severe drug-induced interstitial lung disease (ILD) among patients with breast cancer in Japan. We analyzed a large nationwide database of patients with breast cancer treated with anticancer therapies between 2009 and 2022. ILD was identified using diagnostic codes and treatment records. Of the 81,601 patients, 1042 developed ILD requiring corticosteroids, corresponding to an incidence rate of 1.41 per 100 person-years. The incidence varied across years and treatment regimens. Most ILD incidents occurred within the initial 90-day period post-anticancer therapy initiation. Increase in ILD cases and potential risk variations among treatments underline the importance of continued monitoring, especially during treatment onset, and ILD management in patients with breast cancer undergoing therapy.