Tumor stage-specific trends of sentinel lymph node biopsy for vulvar melanoma (406)

Abstract

<b>Objectives:</b> Vulvar melanoma is a rare and understudied malignancy. Due to its poor prognosis, management has included vulvectomy and complete bilateral inguinofemoral lymphadenectomy. The Standard of care for cutaneous melanomas is to perform sentinel lymph node (SLN) biopsy during excision of intermediate thickness lesions. Lymph node dissection in the inguinofemoral region can result in significant morbidity; thus, the utilization of SLN biopsy for vulvar melanoma is under active investigation. The Standard of care regarding SLN biopsy for vulvar melanoma is not yet determined due to limited prospective data. The objective of this study was to examine the trends and outcomes related to SLN biopsy for vulvar melanoma in the United States according to the local tumor stage. <b>Methods:</b> This population-based retrospective cohort study utilized the National Cancer Institute's Surveillance, Epidemiology, and End Result program from 2004 to 2018. The study population included women with non-metastatic T1-4 stage vulvar melanoma who underwent vulvectomy and had data regarding the method of nodal evaluation. The exposure assignment was based on nodal evaluation: lymphadenectomy, SLN biopsy, or no surgical nodal evaluation. The main outcome was <i>(i)</i> temporal trends of lymphadenectomy or SLN biopsy based on T stage, assessed with a three-year time increment and the Cochrane-Armitage trend test, and <i>(ii)</i> overall survival related to SLN biopsy assessed with inverse probability of treatment weighting propensity score. <b>Results:</b> A total of 729 women with T1-4 vulvar melanoma were examined for analysis. For T1 disease (<i>n</i>=215), the utilization of SLN biopsy significantly increased from 16.7% to 38.9% (<i>p</i>=0.002) over time. For T2 disease (<i>n</i>=156) and T3 disease (<i>n</i>=120), the frequency of SLN biopsy was unchanged during the study period (T2 disease, 22.6% to 26.6%, <i>p</i>=0.279; and T3 disease, 27.3% to 37.0%, <i>p</i>=0.812). For T4 disease (<i>n</i>=238), there was a statistically significant increase in the number of women receiving SLN biopsy from 21.2% to 32.9% (<i>p</i>=0.042) during the study period. Across the four disease groups, the SLN biopsy and LND groups had comparable overall survival in the weighted models (all <i>p</i>>0.05). <b>Conclusions:</b> This large sample size, population-based study found an upward trend in performance of SLN biopsy in both T1 and T4 vulvar melanoma in the past decade in the United States. In T2 and T3 vulvar melanoma, SLN biopsy did not increase. While SLN biopsy is standard in T2-3 cutaneous melanoma, it appears to be less utilized in these tumor stages of vulvar melanoma. Given the significant morbidity associated with inguinal lymph node dissection, further research is warranted on whether these trends have truly resulted in decreased perioperative morbidity.