Validation of the 2021 FIGO staging schema for advanced vulvar cancer

The International Federation of Gynecology and Obstetrics (FIGO) revised the vulvar cancer staging schema in 2021. Previous stage IIIA-B diseases were reclassified based on nodal size (≤5 mm for stage IIIA compared with >5 mm for stage IIIB), and previous stage IVA1 disease based on non-osseous organ extension was reclassified to stage IIIA whereas osseous extension remained as stage IVA. This study sought to validate the 2021 FIGO vulvar cancer staging schema.

This retrospective cohort study examined 889 women with stage III-IV vulvar cancer from 2010 to 2015 in the National Cancer Institute's Surveillance, Epidemiology, and End Results Program. Stage shift and overall survival were assessed by comparing the 2021 and 2009 FIGO staging schemas.

Stage shift occurred in 229 (25.8%) patients (upstaged 17.7% and downstaged 8.1%). When comparing the new and previous staging schemas, 5 year overall survival rates were 45.6% versus 48.9% for stage IIIA, 47.0% versus 44.2% for stage IIIB, and 13.9% versus 25.1% (interval change -11.2%) for stage IVA diseases. According to the revised staging schema, 5 year overall survival rates were similar for stage IVA and IVB diseases (13.9% vs 14.5%) and for stage IIIA and IIIB disease (45.6% vs 47.0%). For new stage IIIA disease, 5 year overall survival rates differed significantly based on the staging factors (nodal involvement vs non-nodal organ involvement, 48.9% vs 38.7%, difference 10.2%, p=0.038).

The 2021 FIGO staging schema results in one in four cases of advanced vulvar cancer being reclassified. Survival rates of patients with new stage IVA disease worsened significantly whereas those of patients with new stage IIIA disease were heterogenous based on the staging factors. The discriminatory ability of the revised 2021 FIGO staging schema for 5 year overall survival rate between patients with stage IIIA and IIIB tumors and those with IVA and IVB tumors is limited in this study population.