Paradigm shift from lymphadenectomy to sentinel lymph node biopsy in vulvar cancer surgery (364)

Abstract

<b>Objectives:</b> To examine trends, characteristics, and outcomes related to nodal assessment for vulvar cancer surgery in the United States. <b>Methods:</b> This is a retrospective observational cohort study querying the National Cancer Institute's Surveillance, Epidemiology, and End Results Program. The study population was 5,604 women with T1b or T2-smaller (<4cm) squamous cell carcinoma of the vulva who underwent primary vulvectomy from 2003-2018. Exposure allocation was based on nodal evaluation type, including lymphadenectomy (LND; <i>n</i>=3,319, 59.2%), sentinel lymph node (SLN) biopsy (<i>n</i>=751, 13.4%), or no surgical nodal evaluation (<i>n</i>=1,534, 27.4%). The main outcomes were <i>1)</i> trends and characteristics related to SLN biopsy assessed by the multinomial regression model, and <i>2)</i> vulvar cancer-specific survival assessed by comparing risk analysis and propensity score weighting. The sensitivity analysis included evaluation of the external cohort with T1a disease (<i>n</i>=1,291). Fig. 1 <b>Results:</b> The utilization of SLN biopsy increased from 5.7% to 23.3% in 2006-2018, while the proportion of LND decreased from 64.1% to 48.8% in 2010-2018 (p<0.05) (top panel). These associations remained independent in multivariable analysis: SLN biopsy use in 2015-2018 versus 2003-2006, with an adjusted-odds ratio of 3.57 (95% CI: 2.54-5.01, p<0.001), and LND use in 2015-2018 versus 2003-2006, with an adjusted-odds ratio of 0.79 (95% CI: 0.63-0.97, p=0.027). In a propensity score weighted model, 5-year cumulative rate for vulvar cancer-specific mortality was 15.2% (interquartile range: 12.1-18.9) for the SLN biopsy group and 16.9% (interquartile range 15.6-18.3) for the LND group (subdistribution-HR [sHR]: 0.90, 95% CI: 0.76-1.06, p=0.217) (bottom panel). Similar association was also observed in T1b disease (sHR: 0.88, 95% CI: 0.70-1.09, p=0.236), T2-smaller (<4cm) disease (sHR: 0.82, 95% CI: 0.50-1.33. p=0.419), and N0 cases (sHR: 0.93, 95% CI: 0.70-1.22, p=0.594). Increasing performance of SLN biopsy was also observed in T1a disease from 1.3% to 7.3% during the study period (p<0.001). <b>Conclusions:</b> The landscape of surgical nodal evaluation is shifting from lymphadenectomy to SLN biopsy in vulvar cancer surgery. This study suggests that an SLN biopsy-incorporated treatment approach is not associated with worse survival compared to LND.