Role of Sentinel Lymph Node Biopsy in Clinically Node Negative Carcinoma Penis - a Prospective Study

Nodal metastasis is a strong prognostic indicator in carcinoma penis, with 25% difference in 5-year cancer-specific survival among node negative and node positive patients. This study aims to assess efficacy of SLNB in identifying occult nodal metastasis (seen in 20-25% of cases), thus avoiding morbidity of prophylactic groin dissection in rest. Study was conducted between June 2016 and December 2019 on 42 patients (84 groins). Primary outcomes assessed were sensitivity, specificity, false negative rates, positive predictive value, and negative predictive value of sentinel lymph node biopsy (SLNB) compared to superficial inguinal node dissection (SIND). Secondary outcomes were to know prevalence of nodal metastasis, sensitivity, specificity, false negative rates, positive predictive value (PPV), negative predictive value (NPV) of frozen section study, and ultrasonography (USG) compared to histopathological examination (HPE) and to evaluate false negative results of fine needle aspiration cytology (FNAC). Patients with impalpable inguinal nodes were subjected to USG and FNAC of suspicious nodes. Only those with non-suspicious USG/negative FNAC were included. Patients who were node positive, had prior chemotherapy/radiotherapy/prior groin surgery, or medically unfit for surgery were excluded. Dual-dye technique was used to identify sentinel node. Superficial inguinal dissection was done in all cases and both specimens were subject to frozen section. If ≥ 2 nodes were involved on frozen section, ilioinguinal dissection was done. SLNB had sensitivity, specificity, PPV, NPV, and accuracy of 100%, respectively. There were no false negative results of frozen section study among 168 specimens. Ultrasonography had sensitivity of 50%, specificity of 48.75%, PPV of 4.65%, NPV of 95.12%, and accuracy of 48.81%. We had 2 false negative results of FNAC. Sentinel node biopsy with frozen section study when done in properly selected cases using dual-dye technique in high volume centers by experienced professionals is a very reliable tool in establishing the nodal status, thereby facilitating need directed treatment, thus prevent either over/under treatment.