Objectives

Following tumour positive sentinel lymph node biopsy (+DSNB), completion inguinal lymph node dissection (ILND) is negative in 84-89% of basins. Thus, ILND after +DSNB may be considered overtreatment resulting in substantial morbidity. This study aimed to develop a predictive model for additional inguinal lymph node metastases (LNM) at ILND following +DSNB using DSNB characteristics to identify a patient group in which ILND might be omitted.

Patients and methods

A retrospective study of 407 inguinal basins with a +DSNB of penile cancer patients who underwent subsequent ILND from seven European centres. From the histopathology reports, the number of positive and negative lymph nodes, extranodal extension and size of the metastasis were recorded. Using bootstrapped logistic regression, variables were selected for the clinical prediction model based on the optimisation of Akaike's information criterion. The area under the curve (AUC) of the receiver operating characteristic (ROC) curve was calculated for the resulting model. Decision curve analysis (DCA) was used to evaluate the clinical utility of the model.

Results

64 (16%) of +DSNB harboured additional LNM at ILND. The number of positive nodes at +DSNB (odds ratio (OR) 2.19; 95% confidence interval (CI) 1.17-4.00; p=0.01) and the largest metastasis size in mm (OR 1.06; 95%CI 1.03-1.10; p=0.001) were selected for the clinical prediction model. The AUC was 0.67 (95%CI 0.60-0.74). The DCA showed no clinical benefit of using the clinical prediction model.

Conclusion

A small but clinically important group of basins harbour additional LNM at completion ILND following +DSNB. While DSNB characteristics were associated with additional LNM, they did not improve the selection of basins in which ILND could be omitted. Thus, completion ILND remains necessary in all basins with a +DSNB.