Next-generation genome sequencing of a matched normal-tumor pair from a patient with intractable gestational choriocarcinoma: A case report

Gestational choriocarcinoma is a gestational trophoblastic neoplasia (GTN) originating from trophoblastic cells with abnormal proliferation. Although chemotherapy is effective for treating this cancer, when patients develop chemoresistance, personalized treatment, such as the use of drugs matching their genomes, is required. The present report describes a case of intractable gestational choriocarcinoma identified using a next-generation sequencing (NGS)-based tumor panel. A 51-year-old woman was diagnosed with gestational choriocarcinoma via pathological and short tandem repeat analyses. The patient did not achieve remission despite many regimens of chemotherapy, including high-dose therapy with autologous peripheral blood stem cell transplantation. To identify drugs tailored to this particular choriocarcinoma, NGS was performed on the tumor of the patient, and the tumor genome was compared with that of the patient's blood sample using the NCC Oncopanel System. Consequently, 245 single nucleotide variants (SNVs) with a mean SNV allele frequency of 63.1% were identified. This high frequency was because the genome of the gestational choriocarcinoma contained part of the genome of the partner. Therefore, our experience of the present intractable case of choriocarcinoma suggested that matched normal-tumor pair analysis is not appropriate for treatment decisions in GTN cases. When using an NGS-based tumor panel to assess choriocarcinoma, researchers must consider whether the genomic DNA of the patient and their partner are involved in the GTN.