Prognostic impact of systematic lymphadenectomy during interval debulking surgery after neoadjuvant chemotherapy in stage III ovarian cancer: A 38-institution retrospective cohort study using inverse probability of treatment weighting.

INTRODUCTION: We evaluated the clinical significance of systematic lymph node dissection (SyLND) during interval debulking surgery (IDS) in patients with stage III ovarian cancer, focusing on subgroups that might benefit from SyLND. METHODS: The multicenter retrospective study included patients with FIGO stage III ovarian, fallopian tube, and primary peritoneal cancers, who underwent IDS following neoadjuvant chemotherapy (NACT), at Gynecologic Cancer Study Group of the Japan Clinical Oncology Group (JCOG-GCSG) institutions between 2017 and 2021. Patients were classified into SyLND and no/selective lymph node dissection (NoLND/SeLND) groups. Progression-free survival (PFS) was the primary outcome, and overall survival (OS) and postoperative complications were secondary outcomes. Inverse probability of treatment weighting was applied. RESULTS: Among 696 eligible patients, SyLND was associated with better PFS (hazard ratio [HR] 0.73, 95% confidence interval [CI] 0.55-0.97) and OS (HR 0.66, 95% CI 0.48-0.92) than NoLND/SeLND. In subgroup analyses of patients achieving complete resection, SyLND yielded no survival advantage in those with clinical-negative nodes (cN0). Conversely, among patients with clinical-positive nodes (cN1) before NACT, PFS and OS favored SyLND, although differences were not statistically significant. Similar trends were observed in cN1 patients whose lymph nodes decreased to <10 mm before IDS. SyLND was associated with higher complication rates. CONCLUSION: SyLND was associated with better PFS and OS in patients with stage III ovarian cancer undergoing IDS. Exploratory subgroup analyses suggested only a favorable but statistically inconclusive trend in patients with cN1. Pre-NACT nodal assessment may help determine the indications for SyLND during IDS.