**4.2 Treatment-related pneumonitis**

In a meta-analysis of 11 clinical trials in patients treated with ICI (PD-1 or CTLA-4 blockade), the use of ICIs led to an increased risk of pneumonitis of all grades [165]. Younger age (<60 years old) may be a major risk factor [166]. Corticosteroids can be used for the treatment of pneumonitis, and those refractory cases should be treated with steroid-free immunosuppressants. For cases of grade 3 or above pneumonitis, potential infections should be considered. In cases of severe pneumonitis, the use of ICI should be stopped [167].
