Abstract
Immune checkpoint inhibitors (ICIs) are used to treat many types of cancers. However, the effect of ICIs on second primary tumors is still unclear. Some studied have concluded that ICIs could reduce the incidence of second primary tumors, while others found an increased overall risk of second primary cancer after the introduction of ICIs to the treatment of melanoma. Here, we report the case of a patient with advanced non-small cell lung cancer (NSCLC) who was treated with ICIs in combination with antiangiogenic drugs, and subsequently developed a second primary tumor in the context of a favorable curative effect of the primary lung cancer. From this case, we know that good efficacy of ICIs for a primary tumor does not mean that a second primary tumor will never develop, which reminds clinicians to consider the possibility of a second primary tumor rather than treating it directly as disease progression.