YO16 - Chemotherapy-resistant epithelioid trophoblastic tumor successfully treated by immunotherapy with further response after dose escalation: a case report

Case summary

Epithelioid trophoblastic tumor (ETT) is the rarest variant of gestational trophoblastic neoplasia (GTN). We hereby present a case of chemotherapy resistant ETT successfully treated with immunotherapy. A 62-year-old female, with a history of hydatidiform mole and underwent total hysterectomy in 21 years ago, was initially admitted to another hospital with a diagnosis of FIGO stage IIIC ovarian cancer and had cytoreduction surgery. The patient was then transferred to our hospital. However, pathology and immunohistochemistry led to a final diagnosis of ETT. Postoperative CT scan showed a recurrent lesion in the pelvis of 6.5 x 3.7cm in size and her βhCG was 4650 mIU/mL. She was treated with EMA-CO for 3 cycles with an initial response but quickly progressed afterwards. She then had a second debulking surgery and one cycle of Paclitaxel-Carboplatin, but the βhCG level surged to 16,026 mIU/mL. We switched chemotherapy to BEP for 4 cycles with a partial response to βhCG of 2252 mIU/mL, followed by EP for 2 cycles. Unfortunately, βhCG level rose back to 2848 mIU/mL. After multiple lines of chemotherapy, pembrolizumab 2mg/kg every 3 weeks was attempted. The disease then responded with βhCG decreasing gradually to 35 mIU/mL after 4 cycles. However, after 3 more cycles of pembrolizumab, βhCG level slowly went up to 870 mIU/mL. The patient refused further chemotherapy due to poor tolerability and wished to continue immunotherapy. We then decided to increase the Pembrolizumab dose to 200mg q3w. Surprisingly, the βhCG went down to 71 mIU/mL after 2 cycles of the new dose. Previous studies showed that PD-L1 is strongly expressed by GTN, hypothetically as a way of maintaining gestational tolerance to maternal immune recognition. There has been an increasing number of reports on immunotherapy for GTN but only a few cases of ETT have been recorded. In our case, we used Pembrolizumab with an initial dose of 2 mg/kg q3wk based on previous choriocarcinoma case reports (PMID: 29185430) but then increased the dose to 200mg q3wk after progression, and interestingly, the patient responded. This might suggest Pembrolizumab 200mg q3wk might be the suitable dose for further prospective studies.

Clinical trial identification

Editorial acknowledgement