Can Adjuvant Chemoradiotherapy Replace Inguinal Lymph Node Dissection after a Positive Sentinel Lymph Node Biopsy in Vulvar Cancer?

Abstract

<h3>Purpose/Objective(s)</h3> The GROINS VII study was stopped early after it was noted that adjuvant radiotherapy to 50Gy prescribed to a CTV designed with fixed margin around the vessels without concurrent chemotherapy resulted in unacceptably higher rates of nodal recurrence compared to inguinofemoral dissection. We aimed to evaluate if the use of higher radiotherapy dose, volumetric CTV design based on muscular borders, and integrations of chemotherapy would impact the conclusion that radiotherapy cannot replace inguinal lymph node dissection <h3>Materials/Methods</h3> Patient receiving post-operative radiotherapy after sentinel lymph node biopsy alone (without inguinal lymph node dissection) from 2010-2020 were retrospectively reviewed. Adjuvant radiotherapy typically consisted of 50Gy to the inguinal regions with a simultaneous integrated boost to 55-57.5Gy in 25 fractions to any imaging enlarged nodes with concurrent weekly cisplatin at 40mg/m2 unless contraindicated. All included patients also received radiotherapy to the primary site of vulva and pelvic nodes. The primary endpoint was patterns of recurrence. Due to small number of events, no multivariant model was performed. To quantify the difference in inguinal nodal CTV design between the GROINS VII protocol, CTVs were retrospective completed as per the original GROINS VII, and compared using paired <i>t</i> test. <h3>Results</h3> Nine patients with inguinal nodal macrometastasis after sentinel lymph node biopsy alone were identified. Median tumor size was 2.0cm (IQR: 1.5-2.8 cm). The median number of positive sentinel lymph nodes were 1 (IQR: 1-2) with a median macrometastasis size of 5mm (IQR: 4-11mm). No patient had extracapsular extension. Median size of boosted inguinal nodes was 3.7cm (IQR: 1.7-9.1). At a median follow up of 18 months (IQR: 5-46), 1 (9%) patient had inguinal node recurrence, however that patient stopped radiotherapy at 43.2Gy due to bleeding gastric ulcer requiring surgical intervention. None of the patients (0%) who completed the prescribed radiotherapy had inguinal nodal recurrence. The median inguinal CTV volumes used herein were 295cc (IQR: 232-349) compared to 139cc (IQR: 133-166) if completed using fixed margins from the original GROINSVII, <i>p=</i>0.002. <h3>Conclusion</h3> This data set supports the hypothesis of GROINS VIII that higher dose, larger CTV margins, and integration of chemotherapy may impact the conclusion that radiotherapy cannot replace inguinal lymph node dissection.