Radiotherapy and immunotherapy for oligometastatic hepatoid adenocarcinoma arising from endometriosis: a case report

Abstract Objectives Hepatoid adenocarcinoma (HAC) arising from endometriosis is an extremely rare malignancy with a poor prognosis and no standard treatment. Radical surgical resection followed by chemotherapy is the commonly used treatment for HAC. The role of radiotherapy and immunotherapy has been poorly explored. We report the second case of HAC arising from endometriosis with oligometastatic lung progression to share our experience with a multimodal approach. Case presentation We report a case of an HAC arising from endometriosis in a patient who presented with a pelvic mass and markedly elevated Alpha-fetoprotein (AFP) and underwent surgical resection followed by pelvic radiotherapy and chemotherapy. The patient had satisfactory pelvic control but developed a solitary lung metastasis six months after the completion of first-line therapy, which was treated with stereotactic body radiotherapy (SBRT). The second metachronous lung metastasis subsequently appeared and was also treated with SBRT, followed by immunotherapy and targeted therapy. The lung metastasis achieved a complete response, and the patient remained free of disease for over 36 months. Treatment-related pneumonitis occurred and resolved after corticosteroid therapy and immunotherapy discontinuation. Conclusions HAC arising from endometriosis appears to be prone to metastasis. The multimodal strategy integrating surgery, chemotherapy, radiotherapy, immunotherapy and targeted therapy may offer durable disease control in oligometastatic HAC arising from endometriosis, though the contribution of each component requires further investigation. Clinicians should also be aware of the risk of pneumonitis when combining lung SBRT with immunotherapy.