Inguinofemoral sentinel lymph node biopsy by scar injection in vulvar cancer: an assessment of feasibility and long-term outcomes

BACKGROUND: Performing inguinofemoral sentinel lymph node biopsy for vulvar cancer following a previous vulvar excision, often referred to as 'scar injection', is debated. OBJECTIVE: To assess the feasibility of sentinel lymph node biopsy following scar injection and the long-term outcomes in patients undergoing this procedure. METHODS: We conducted a retrospective observational cohort study of patients with vulvar cancer. We assessed detection rates and outcomes in patients who underwent sentinel lymph node biopsy by scar injection and compared them with patients who had injection around a visible tumor and with patients who had an inguinofemoral lymphadenectomy following previous vulvar excision. Sentinel node detection rates are described per patient and per groin and are compared using Χ² analysis. Cox regression analysis was used to assess the association of recurrence and survival with surgical technique and recognized pathological variables. RESULTS: Data were analyzed for 173 groins in 97 patients. At least one sentinel lymph node was detected in 162 (94%) groins examined, and detection rate did not differ whether the groin was assessed following tumor injection (n=122, 94%) or scar injection (n=40, 93%; p=0.85). Patients in the scar-injection group had less frequent lymph node metastases (p<0.02), smaller tumors (p<0.001), and more superficial invasion (p<0.02). Median follow-up was 34.7 months (range 0-108). Scar injection was not independently associated with recurrence or death on multivariable analysis, and depth of invasion was the only independent predictor of disease recurrence (hazards ratio (HR)=1.14, p=0.03). Recurrence and survival were also comparable for patients who had a sentinel lymph node biopsy or inguinofemoral lymphadenectomy following previous vulvar excision (log rank p=0.30; p=0.67). CONCLUSIONS: Sentinel lymph node biopsy by scar injection is feasible and demonstrates similar long-term outcomes in patients having scar or tumor injections, and in patients following previous tumor excision undergoing sentinel lymph node biopsy or lymphadenectomy.