Introduction/Background Sentinel node biopsy (SNB) in vulvar cancer reduces morbidity. However, the oncological safety in tumours ≥4cm and in multifocal tumours has not been systematically studied. Since 2017, vulvar cancer treatment in Sweden is centralised to four university hospitals. All cases of primary or recurrent vulvar cancer are discussed at weekly national multidisciplinary conferences.

The aim of this study was to investigate the feasibility and oncological safety of SNB in vulvar squamous cell carcinoma (VSCC) with tumours ≥4cm, or multifocal disease.

Methodology In this prospective nationwide pilot study, women with primary VSCC ≥4cm (group 1) or multifocal tumours (group 2) diagnosed between December 2019 and December 2022, without clinical or radiological signs of dissemination, underwent both SNB and inguinofemoral lymphadenectomy. Detection rates, negative predictive values, and the prevalence of metastases (isolated tumour cells (ITC), micro- and macrometastases) were determined for each of the two groups.

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Abstract #92 Figure 1

Distribution of lymph node metastases in the subgroups: A. Tumours =4cm, n=36 (58/69 groins with successful sentinel mapping) B. Multifocal tumours, n=17 (29/34 groins with successful sentinel mapping)

Results 36 women were included in group 1 and 17 women in group 2. The detection rates varied between 94–100% per patient and 84–85% per groin. There were no false negative sentinel nodes, giving a negative predictive value of 100% (95% CI 91.2–100 for group 1, 95% CI 83.9–100 for group 2). 47% of the women had lymph node metastases, 15% ITC or micrometastases only. The sentinel node metastases were the only metastatic nodes in 83% of all groins. Metastatic disease was found in 4 out of 16 (25%) non-mapping groins, in all but one with extranodal growth.

Conclusion In a centralised health care system with high proficiency, SNB seem to be feasible in tumours ≥4cm and multifocal disease. The procedure can be performed with high detection rates and promising oncological safety. Furthermore, SNB increases precision by detection of low-volume metastases. In non-mapping groins, an inguinofemoral lymph node dissection is mandatory to prevent undiagnosed advanced disease.