Low-grade serous ovarian cancer: 2026 expert consensus report

Low-grade serous ovarian carcinoma (LGSOC) is a rare epithelial malignancy characterized by frequent mitogen-activated protein kinase (MAPK) pathway alterations, hormone receptor expression, relative resistance to cytotoxic chemotherapy, and a prolonged, relapsing clinical course. Since publication of the 2023 international expert consensus, significant advances have reshaped the management of both newly diagnosed and recurrent disease. The 2026 LGSOC Consensus Conference convened an international multidisciplinary panel of experts in the field to review emerging evidence and update recommendations across pathology, molecular testing, translational biology, frontline and recurrent treatment, imaging, treatment-associated toxicity, regulatory strategy, patient advocacy, and future research priorities. Recommendations were informed by contemporary clinical evidence, multidisciplinary discussion, and patient perspectives. The updated consensus incorporates practice-changing data from NRG-GY019 supporting chemotherapy-containing postoperative therapy as the current reference approach for stage II-IV disease while recognizing selected circumstances in which endocrine monotherapy may represent individualized de-escalation. It also integrates recent advances in recurrent disease, including the US Food and Drug Administration's accelerated approval of avutometinib in combination with defactinib for KRAS-mutated LGSOC, emerging evidence supporting endocrine therapy combined with CDK4/6 inhibition, and refined guidance for biomarker-directed treatment selection, imaging assessment, toxicity management, and patient-centered survivorship. The panel emphasizes treatment-specific biomarker interpretation, multidisciplinary care, central pathology review for clinical trials, and the continued need for prospective studies addressing treatment sequencing, predictive biomarkers, and quality-of-life outcomes. This updated international consensus provides an evidence-based framework for the diagnosis and management of LGSOC while identifying priorities for future clinical research and drug development.