A Case Report of Metastatic Gastric Cancer Treated with Pembrolizumab during Pregnancy.

Introduction: Immune checkpoint inhibitors are extensively used in present-day clinical practice for treating many types of cancers at different stages. To date, there are scarce data on the use of immunotherapy in pregnancy. Immune-related adverse events are a typical consequence of this therapy miming autoimmune diseases.

Case presentation: A 35-year-old woman (G1P0) diagnosed with gastric carcinoma underwent neoadjuvant chemotherapy followed by surgery. During follow-up, axillary metastasis was discovered, radiotherapy failed, and consequently immunotherapy was started. Concurrently, pregnancy ensued. Despite potential risks, the patient opted to continue immunotherapy and the pregnancy. At 31 weeks, fetal bowel dilation was noted. Subsequently, the fetus also developed fetal growth restriction. A cesarean section was performed at 35 weeks. The newborn required repeated bowel resections for necrotizing enterocolitis, necessitating extensive medical intervention. The mother continues pembrolizumab treatment with a positive response.

Conclusion: To the best of our knowledge, this might constitute a possible case of a fetal immune-related adverse event after immunotherapy in utero exposure.