Symptomatic pseudo-progression followed by significant treatment response in two lung cancer patients treated with immunotherapy.

In the setting of pseudo-progression in a cancer patient who receives immunotherapeutic treatment, discontinuation of therapy is recommended if the patient is symptomatic. Here, we present two patients with advanced adenocarcinoma of the lung who developed massive tumor growth after initiation of treatment with the anti-PD-1 antibody pembrolizumab. Even though clinical deterioration occurred in the form of severe dyspnea and weight loss, pembrolizumab therapy was continued, as the speed of tumor growth suggested pseudo-progression and the tumors showed marked PD-L1 expression. This approach was successful, and both patients experienced impressive treatment responses within a few weeks.