Prognosis of isolated groin recurrence following sentinel lymph node biopsy in primary node-negative vulvar cancer.

e17650 Background: In early-stage vulvar cancer, sentinel lymph node biopsy (SNB) is an accepted method for surgical staging of the groin lymph nodes. However, the risk for groin recurrence is higher compared to full dissection of the groin. To weigh risks and benefits, data on prognosis after isolated groin recurrence following a negative SNB are missing. Methods: This retrospective, multicenter AGO study group study included patients (pts) with primary node-negative vulvar cancer who underwent local tumor resection and negative SNB only between 2010 and 2021, and later developed isolated groin recurrence. Baseline characteristics, treatment, and outcome were collected. Results: As of January 2025 , 43 pts with FIGO stage I disease with isolated groin recurrences were included in the analysis. Initially, all pts underwent local tumor resection and negative SNB without additional treatment. Isolated groin recurrences occurred after a median of 12 months (range: 3–83 months), with 83.7% of recurrences observed within the first two years. Most pts (24/43; 55.8%) presented with symptoms such as pain, a palpable tumor, or ulceration, while 15 (15/43;34.9%) pts were asymptomatic and diagnosed during routine follow-up (FU). The median FU period after groin recurrence was 16 months (range: 2–123 months). At last FU, 17 pts (39.5%) had died: 9 (20.9%) due to tumor-related causes, 6 (14.0%) from unknown causes, and 2 (4.7%) for other reasons not associated with disease. Of the remaining pts, 20 (46.5%) were alive without evidence of disease; while 2 (4.7%) were alive with disease recurrence. The status of 4 pts (9.3%) was unknown. The estimated 18-months overall survival (OS) was 55.8%. One pt died from bleeding related to femoral vessel infiltration before treatment could be initiated. Of the 42 treated pts, 35 underwent inguinofemoral lymphadenectomy (ifLAE), with 23 undergoing unilateral and 12 bilateral dissection. Among these pts, 22 received subsequent radiotherapy, of whom 9 were alive in remission (40,1%) and 12 had died (57.1%) at last FU; 1 had an unknown status. Thirteen pts received chemoradiation after ifLAE, with 10 alive and in remission (76.9%), 1 experiencing progressive disease, and 2 with unknown status. Seven pts (7/42, 16,6 %) did not undergo ifLAE due to comorbidities and received only radiation (4 pts) or chemoradiation (3 pts). In this group, 3 (37.5%) were alive in remission, 1 (12.5%) had progressive disease, 1 (12.5%) had an unknown status, and 3 (37.5%) died. Conclusions: The majority of groin recurrences following a negative SNB occurred within the first two years post-diagnosis. While prognosis appears improved compared to recurrence after prior full groin dissection, it is still impaired, with an 18-month OS of 55.8%. The combination of ifLAE and chemoradiation seems to provide the most favorable outcome.