Pediatric primary extragonadal choriocarcinoma - A study on male patients at a single tertiary medical institution.

Background: Primary extragonadal choriocarcinoma (PEGCC) in male is rare. It is highly malignant, typically presents with distant metastasis at the time of diagnosis, and responds poorly to treatment. Because of its associated high levels of PD-L1, the PD-1/PD-L1 pathway is a likely therapeutic target. Herein, we report our experience of treating pediatric PEGCC in six boys at a tertiary hospital.

Methods: We analyzed the data of six boys with pathologically confirmed PEGCC between 2009 and 2021. Their clinicodemographic and histopathological characteristics as well as treatments and clinical outcomes were retrieved from their medical charts.

Results: The patients' median age was 15 (range: 12-17) years. The most common primary tumor site was the mediastinum (67%, 4/6), with one case each in the retroperitoneum (16.7%) and brain (16.7%). Except for the patient with brain PEGCC, all presented with metastasis at the time of diagnosis. The following metastatic sites were observed: the lungs (100%, 5/5), brain (3/5, 60%), liver (3/5, 60%), kidneys (2/5, 40%), and spleen (1/5, 20%). Most patients had dry cough, dyspnea, and hemoptysis at initial presentation, likely due to lung metastasis. Serum human chorionic gonadotropin (HCG) levels were highly elevated in all patients. All patients received platinum-based cytotoxic chemotherapy. The patient with brain choriocarcinoma underwent surgical tumor resection; all others underwent only surgical biopsy. Strong positive PD-L1 immunohistochemical staining was noted for two patients. One patient received the PD-L1 inhibitor pembrolizumab and achieved a good response. Our cohort's 1-year survival rate was 33.3%, with a median survival of 4.34 months. Serum HCG levels remained normal in the two survivors during follow-up visits.

Conclusion: The poor response to current platinum-based chemotherapy remains a major challenge in the management of pediatric PEGCC. Adding pembrolizumab to a conventional chemotherapy regimen may improve the outcomes in boys with PEGCC.