[Pneumonitis Induced by Immune Checkpoint Inhibitors]

Immune checkpoint inhibitors(ICIs)have shown efficacy in many clinical trials and have an important role in the treatment for advanced cancers.Many physicians recently have chances to use ICIs across tumor types.ICIs are associated with a unique set of toxic effects, which are defined as immune-related adverse events(irAEs).Drug -induced pneumonitis is considered to be one of important irAEs.Pneumonitis as irAE has been not so frequently observed, and all Grade in 0~10%and Grade 3 or 4 in 0~3% of patients receiving ICIs.However severe or life-threatening pneumonitis was observed in some cases, so that pneumonitis caused by ICIs has been clinically important.The incidence of pneumonitis caused by ICIs for Japanese patients is similar to previous reports.Symptoms of pneumonitis by ICIs are considered to be dyspnea and cough.Some patients are diagnosed as asymptomatic pneumonitis with abnormal radiographic findings.Cryptogenic organizing pneumonia(COP) pattern has been reported to be most frequently observed in radiographic patterns of pneumonitis caused by ICIs(43~65%). Since some cases shows pneumonitis with different radiographic pattern from other drug-induced pneumonitis, blood test and bronchoscopy may be useful for diagnosis.It has been recommended to treat patients with ICIs-related pneumonitis according to severity of pneumonitis.In most patients, pneumonitis is improved with corticosteroids and withdrawal of ICIs, though a few patients with severe pneumonitis may need immunosuppressants.It has been recommended for medical oncologists to consult and cooperate with pulmonologists for diagnosis and treatment of ICIs-related interstitial lung disease(ILD). The mechanism of pneumonitis induced by ICIs may differ from those of other drug-induced pneumonitis.Therefore, medical oncologists should be careful for ICIs-related pneumonitis as a new disease category in the treatment of ICIs.