Amrubicin-Induced Radiation Recall Pneumonitis After Low-Dose Palliative Thoracic Radiotherapy: A Case Report

A 70-year-old man with extensive-stage small-cell lung cancer received palliative thoracic radiotherapy to a total dose of 18 Gy in six fractions for central airway stenosis.Five months later, second-line amrubicin was initiated.After two courses of treatment, he was admitted with fever and cough and was initially treated for suspected bacterial pneumonia.Despite cefepime treatment, computed tomography revealed worsening pulmonary opacities corresponding to the previously irradiated field.Bronchoscopy showed no visible endobronchial tumor, cytology revealed no malignant cells, and microbiological studies were negative.Amrubicin-induced radiation recall pneumonitis (RRP) was clinically diagnosed.Amrubicin was discontinued, and oral prednisolone was initiated at 30 mg/day, resulting in rapid clinical and radiographic improvement.Prednisolone was subsequently tapered to 10 mg/day without radiographic worsening at that dose.This case highlights that RRP should be considered after amrubicin therapy, even when the previous thoracic radiation dose was relatively low.