Abstract
Immunotherapy has revolutionized the treatment of non-small cell lung cancer; however, its role in the treatment response of lung brain metastasis is unknown. Understanding immunotherapy activity in the central nervous system is important in order to avoid additional toxicity, such as that associated with the use of cerebral radiotherapy. We present two cases with clinical and radiological progression with increases in size and perilesional edema of brain lesions after treatment with a combination of ipilimumab and nivolumab. The increasing use of immunotherapy in lung cancer requires increased knowledge of new patterns of radiological response, such as pseudoprogression.