Pseudoprogression during successful rechallenge of immune checkpoint inhibitor in a NSCLC patient.

Rechallenge of immune checkpoint inhibitors (ICPIs) is one of the attractive but unestablished treatment for recurrent non-small cell lung cancer (NSCLC) patients who have been treated with several-lines of systemic chemotherapy. In some NSCLC patients, effects of ICPI rechallenge therapy have become apparent. In ICPI treatment, although very rare, a phenomenon called pseudoprogression is known. We report the first case of a patient who had pseudoprogression during successful rechallenge of ICPI in a NSCLC patient. Although not fully clarified, factors related to the onset of pseudoprogression and good response to ICPI rechallenge are being investigated. Our case showed that pseudoprogression could be developed even in patients with ICPI rechallenge therapy.