Lymph node ratio in inguinal lymphadenectomy for squamous cell vulvar cancer: Results from the AGO-CaRE-1 study.

OBJECTIVE: Lymph node ratio (LNR) can predict treatment outcome and prognosis in patients with solid tumors. Aim of the present analysis was to confirm the concept of using LNR for assessing outcome in patients with vulvar cancer after surgery with inguinal lymphadenectomy in a large multicenter project.

METHODS: The AGO-CaRE-1 study multicenter database was used for analysis. LNR was defined as ratio of number of positive lymph nodes (LN) to the number of resected. Previously established LNR risk groups were used to stratify patients. LNR was investigated with respect to clinical parameters. Univariate and multivariable survival analyses were performed to assess the value of LNR in order to predict overall (OS) and progression-free (PFS) survival.

RESULTS: In total, 1047 patients treated with surgery including inguinal lymph node resection for squamous cell carcinoma of the vulva were identified from the database. Of these, 370 (35.3%) were found to have positive inguinal LN. In total, 677 (64.7%) had a LNR of 0% (N0), 255 (24.4%) a LNR of >0% < 20%, and 115 (11%) a LNR of ≥20%. Patients with higher LNR were found to have larger tumor size (P < .001), advanced tumor stage (P < .001), high tumor grade (P < .001), and deep stromal invasion (P < .001), more frequently. Three-year PFS rates were 75.7%, 44.2%, and 23.1% and three-year OS rates were 89.7%, 65.4%, and 41.9%, in patients with LNRs 0%, >0% < 20%, and ≥20%, respectively (P < .001, P < .001). On multivariable analyses LNR (HR 7.75, 95%-CI 4.01-14.98, P < .001), FIGO stage (HR 1.41, 95%-CI 1.18-1.69, P < .001), and patient's performance status (HR 1.59, 95%-CI 1.39-1.82, P < .001), were associated with PFS. In addition, LNR (HR 12.74, 95%-CI 5.64-28.78, P < .001), and performance status (HR 1.72, 95%-CI 1.44-2.07, P < .001) were also the only two parameters independently associated with OS. LNR generally showed stronger correlation than number of affected LN when comparing the two different multivariable models.

CONCLUSIONS: In women with vulvar cancer LNR appears to be a consistent, independent prognostic parameter for both PFS and OS and allows patient stratification into three distinct risk groups. In survival analyses, LNR outperformed nodal status and number of positive nodes.