A Nomogram to Predict the Duration of Drainage in Patients With Penile Cancer Treated With Inguinal Lymph Node Dissection

Abstract

We developed a nomogram to predict the duration of drainage in patients with penile cancer treated with inguinal lymph node dissection. A total of 111 groin basins in 56 patients who underwent radical inguinal lymph node dissection for penile cancer were retrospectively assessed. We retrieved the clinicopathological factors from the medical records including age, body mass index, albumin, smoking history, hypertension, diabetes, preoperative radiotherapy/chemotherapy, palpable lymph nodes, previous lymph node biopsy, total number of resected lymph nodes and ratio of positive lymph nodes. The criterion of drain removal was total drain output of 50 ml or less per day for 2 days starting from postoperative day 3. A multivariate Cox proportional hazards model was used to explore the risk factors of drainage duration and variable selection was performed according to Akaike's information criteria. A nomogram was built based on regression coefficients and internally validated with 200 bootstrap resamples. Median postoperative drainage duration was 7 days. The prediction model using pretreatment factors showed a concordance index of 0.55. With the addition of lymph node related variables a second model was constructed which produced a better concordance index (0.65) and good calibration. On multivariate analysis young age, high body mass index, total number of resected lymph nodes and ratio of positive lymph nodes were independent predictors of prolonged lymphatic drainage. On the basis of readily obtained clinicopathological variables we developed a nomogram to predict the duration of lymphatic drainage which, if externally validated, could be helpful for patient consultation, treatment decision making and clinical trial design.