Dual Checkpoint Inhibition with Ipilimumab plus Nivolumab After Progression on Sequential PD‐1/PDL‐1 Inhibitors Pembrolizumab and Atezolizumab in a Patient with Lynch Syndrome, Metastatic Colon, and Localized Urothelial Cancer

Immune checkpoint blockade (ICB) is an approved therapy for advanced metastatic mismatch repair (MMR)‐deficient cancer regardless of tissue of origin. Although therapy is effective initially, recurrence rates are significant, and long‐term outcomes remain poor for most patients. It is not currently recommended to give sequential ICB for advanced MMR‐deficient colorectal cancer (CRC) or for patients with metastatic cancer from Lynch syndrome. The need for subsequent therapy options in advanced MMR‐deficient cancer beyond the first ICB regimen arises in clinical practice, and there are often no effective standard chemotherapies or other targeted therapies. We report the case of a Lynch syndrome patient with metastatic CRC and urothelial cancer who was treated sequentially with pembrolizumab (targeting PD1), atezolizumab (targeting PD‐L1), brief rechallenge with pembrolizumab, and finally the combination of ipilimumab (targeting CTLA‐4) and nivolumab (targeting PD1). Over a 28‐month period the patient experienced prolonged disease control with each different regimen the first time it was given, including metabolic response by positron emission tomography and computed tomography scanning and tumor marker reductions. The case suggests that some patients with advanced MMR‐deficient CRC may experience meaningful clinical benefit from multiple sequential ICB regimens, a strategy that can be further tested in clinical trials. KEY POINTS. The case exemplifies clinical benefit from sequential immune checkpoint blockade in a patient with Lynch syndrome with advanced metastatic colorectal cancer and urothelial cancer. Metabolic response, with decreased fluorodeoxyglucose avidity on positron emission tomography and computed tomography, and reductions in tumor markers, such as carcinoembryonic antigen, were helpful in this case to monitor disease status over a 28‐month period of therapy. The concept of sequential immune checkpoint blockade in patients with advanced mismatch repair‐deficient cancer merits further study to determine which patients are most likely to benefit.