Ongoing Radiographic Response for Over 20 Months in Metastatic Cancer Without Continued Immune Checkpoint Inhibitor (ICI) Dosing

Non-small cell lung cancer (NSCLC) frequently presents with overt metastatic spread, portending a negative prognosis. Conventional treatments include chemotherapeutic agents and molecularly targeted and/or immunotherapeutic agents. Most responders to systemic chemotherapy in metastatic disease experience progression shortly after treatment discontinuation and it is very unusual for a patient to continue to manifest ongoing regression of malignant lesions unless treatment is continued. Moreover, responses occur early during therapy, typically within two to four months, and rarely continue beyond that time frame. In this study, we describe a 67-year-old man with stage IV spindle cell cancer (initially diagnosed as NSCLC) who demonstrated ongoing radiographic regression over 20 months after receiving only a single dose of an immune checkpoint inhibitor (ICI) without any additional systemic therapy. Conventional approaches would have continued the ICI and credited any ongoing response to multiple doses. However, this case emphasizes that short exposure to ICI may be sufficient in select circumstances. Given that the five-year survival rate for stage IV non-small cell lung cancer (NSCLC) has historically been below 5%, observing such a durable response highlights the potential for more individualized immunotherapy strategies.