Charcoal Carbon Black Dye Use in Sentinel Lymph Node Mapping in Early Stage Vulvar Cancer (IFLND)

Vulvar cancer is a rare malignancy constituting approximately only 4% of all gynaecological malignancies. Treatment depends on histopathology and stage with surgery being the primary treatment modality in early stages with or without adjuvant radiotherapy depending on tumor margin status and involvement of inguinofemoral lymph nodes. Bilateral or unilateral surgical evaluation of inguinofemoral lymph nodal basin is an important part of the surgical procedure in early stage disease besides vulvar surgery since metastatic involvement dramatically changes stage, adjuvant treatment and surveillance. The usual method for surgical evaluation of inguinofemoral lymph nodes is full inguinofemoral lymph node dissection (IFLND). However, IFLND is highly related to complications such as lymphedema, incisional detachment, lymphocyst formation, lymphangitis, vessel injury and deep venous thrombosis. Over the last 10-15 years sentinel lymph node biopsy of inguinofemoral lymph nodes became a well-accepted form of surgical evaluation procedure instead of IFLND.

The present guidelines offer sentinel lymph node biopsy using various tracers and dyes used alone or in combination (either a blue dye or indocyanine green -ICG (indocyanine green) - is offered in addition to radiocolloid tracer). However, radiocolloid and ICG tracers requires expensive equipment and cumbersome procedures. On the contrary, sterile charcoal carbon dye is inexpensive and does not necessitate any further equipment to be detected. It is actually used to mark the point of resection of colon during colorectal surgery by general surgeons which is injected to the colonic mucosa preoperatively by colonoscopy.

The aim of the present study is to investigate the sensitivity, specificity, negative predictive value and positive predictive value of using charcoal carbon dye as a sentinel tracer in IFLN basin. Early-stage primary vulvar tumors less than 4 cm with any histology but without any clinically or radiographically detectable inguinofemoral lymph nodes will be included into study. Peritumoral four quadrant injections of carbon dye each 0.5 cc or two injections of 3 and 9 o'clock each 1 cc will be given. Following a 20 min interval inguinofemoral area will be dissected and full lymphadenectomy will be performed irrespective of sentinel lymph node recovery since bilateral or unilateral full inguinofemoral lymph node dissection is done in the department of the study so far. Detection rate and other parameters (sensitivity, specificity and etc.) will be compared to results of pathologic evaluation of full IFLND.

Investigators are currently two ongoing studies using charcoal carbon dye as a sentinel tracer to investigate its effectiveness compared to ICG (one in endometrial cancer and the other in ovarian cancer). Both studies are registered to ClinicalTrials.gov (NCT06163963 and NCT05927818). This will be the third of the study series using charcoal carbon dye as sentinel lymph node mapping method in gynecologic cancers (Forth one will be registered in ClinicalTrials.gov shortly in cervical cancers compared to ICG).