Primary lung cancer with delayed drug-induced interstitial lung disease after neoadjuvant chemoimmunotherapy: a case report

Neoadjuvant chemoimmunotherapy is becoming a mainstream treatment for primary lung cancer; however, delayed immune-related adverse events occurring at 3 months or more after discontinuation of treatment have not been reported in this patient population. A 64-year-old man underwent bronchoscopic biopsy, revealing a lung adenocarcinoma (cT4N0M0, stage IIIA), and was treated with three courses of carboplatin, pemetrexed, and nivolumab as neoadjuvant chemoimmunotherapy. Four months after the first course of treatment, the patient underwent a left upper lobectomy with lymph node dissection. Although postoperative hoarseness occurred as a complication, he was discharged on postoperative day 12. On postoperative day 56, the patient developed shortness of breath. An increased inflammatory response and infiltrates in the right lower lobe suggested aspiration pneumonia; however, his condition failed to improve after 1 week of antibiotic therapy. Elevated KL-6 levels and worsening of a right lower lobe interstitial shadow were observed. On day 104 after immunotherapy, the patient was diagnosed with delayed drug-induced interstitial lung disease, and steroid therapy resulted in improvement. In patients with a history of immune checkpoint inhibitor (ICI) administration, attention must be paid to the occurrence of immune-related adverse events, regardless of the duration of ICI administration or the time elapsed since discontinuation, and when diagnosed, treatment should be initiated immediately in accordance with guidelines.