Individualized prediction of the risk of inguinal lymph node metastasis in patients with squamous cell carcinoma of penile

Objective To investigate the independent predictors of inguinal lymph node metastasis (LLM) in patients with penile squamous cell carcinoma (SCCP), and to establish a nomogram for predicting individual LLM risk. Methods The data of patients with SCCP diagnosed at the department of urology, Xijing Hospital from July 2009 to June 2019 were analyzed retrospectively. A total of 101 patients were included in this study, with age of 55 (26-84) years. There were 25 (24.8%) and 76 (75.2%) patients with and without palpable inguinal lymph node enlargement, respectively. There were 47 cases (46.5%), 40 cases (39.6%) and 14 cases (13.9%) in T1, T2 and T3 stages, respectively; there were 67 cases (66.3%), 21 cases (20.8%) and 13 cases (12.9%) in Broder 1, 2 and 3, respectively. The average value (or median) of fibrinogen was 2.84 (1.72-5.00)g/L; alkaline phosphatase was 80(32±214)U, hemoglobin was 147(81-180)g, platelet count was (193.74±65.68×109/L, absolute value of neutrophils, monocytes and lymphocytes were 3.98(1.19-11.85)×109/L, 0.44(0.17-1.90)×109/L and 1.68(0.58-4.13)×109/L, respectively. The average (or median) value of PLR, NLR and LMR were 113.38(18.80-418.42), 2.42(0.59-10.22) and 3.84 (1.08-9.89), respectively. There were 26 cases (25.7%) with LLM and 75 cases (74.3%) without LLM. The independent predictors of LLM were identified by univariate and multivariate logistic regression analyses. The R software was used to establish the nomogram by integrating all independent predictors, and the bootstrap method was used to internally validated our nomogram, where the value of AUC (area under the ROC curve) was calculated and the calibration plot was drawn. Results Clinical inguinal lymph node status (P<0.006), T stage (P<0.021), Broder grade (P<0.017) and absolute neutrophil value (P<0.043) were independent predictors of LLM. The accuracy of our nomogram was 0.875 (AUC=0.875, 95%CI 0.859-0.891); Moreover, the risk of LLM predicted by nomogram was in good consistency with the actual LLM rate, and the errors of the nomogram-predicted LLM risks were all within 10%. Conclusions Clinical inguinal lymph node status, T stage, broder grade and absolute value of neutrophils were identified as independent predictors of LLM in patients with SCCP on the basis of single center data. A generic nomogram predicting LLM risk for Chinese patients was developed, which would be helpful to screen SCCP patients who need prophylactic inguinal lymph node dissection. Key words: Penile neoplasms; Squamous cell carcinoma; Inguinal lymph node metastasis; Nomogram