Effective treatment of steroid-resistant immune checkpoint inhibitor pneumonitis with mycophenolate mofetil

Insufficient evidence is available for treating steroid-resistant immune checkpoint inhibitor pneumonitis (CIP). Although guidelines recommend the use of immunosuppressants, the efficacy of mycophenolate mofetil (MMF) has not been sufficiently verified. We report two cases of steroid-resistant CIP treated with MMF. Both patients responded to initial treatment with prednisolone (PSL), but the CIP flared up repeatedly as the steroids were gradually tapered off. Upon receiving MMF in addition to PSL, their subjective symptoms improved, and the shadows gradually disappeared, allowing for a reduction in the steroid dose. Ultimately, no CIP recurrence was observed despite discontinuing PSL and MMF. Both cases were completely resolved by treatment with MMF. This indicates that MMF may be effective in treating steroid-resistant CIP. In the future, the effects and safety of MMF should be investigated in large-scale clinical trials targeting patients with steroid-resistant CIP.

Difficulties in differentiating between checkpoint inhibitor pneumonitis and lung metastasis in a patient with melanoma

The use of immune checkpoint inhibitors is associated with significant toxicities such as pneumonitis; the clinical presentation of the latter can be misleading and may mimic metastasis. We report the case of a melanoma patient who developed late-onset pneumonitis after discontinuation of treatment with anti-programmed cell death protein 1 (PD1) and anti-cytotoxic T lymphocyte antigen 4 (CTLA4) (patient had a complete response). The patient was asymptomatic, however, surveillance computed tomography (CT) scan showed a growing lung nodule and several new-onset, small lung lesions highly suspicious for recurrence. A biopsy of the lesions revealed organizing pneumonia with absence of malignant cells. The lung lesions completely resolved after 6 months without any intervention. The patient is still in complete remission 2 years after the initial diagnosis of melanoma.