Vulvar cancer is the fourth cause of genital cancer in women, after endometrial, cervical, and ovarian cancer. Its incidence varies across series between 0.5 and 3 per 100,000 women per year. Survival in vulvar cancer is directly related to the extent of the disease. Five-year survival is approximately 90% for stages I and II, but when there is metastatic lymph node disease, only a third of patients survive to 5 years. Approximately 30% of inguinal lymphadenectomies due to vulvar cancer show metastasis, this finding being the main prognostic factor for the disease; hence, lymph node analysis is essential in most cases [1]. Traditional inguinofemoral lymphadenectomy is associated with high morbidity and a major impact on quality of life in vulvar cancer patients who are predominantly elderly.

Seeking to reduce these rates of morbidity, the SLN detection technique was developed, and it has been accepted and standardized in patients with early-stage vulvar cancer. Since the first publications by Levenback et al. and Decesare et al. [2,3] and then those of the GROINSS [4] and GOG [5] research groups and Slomovitz et al. [6], numerous prospective studies have confirmed that the SLN technique in selected cases of vulvar cancer has a high sensitivity, which ensures the safety of the technique. The pooled sensitivity of SLN detection is 91% (85%–95%), with a negative predictive value of 95.6%. Finally, it has been shown that this technique reduces short- and long-term morbidity [[2], [3], [4], [5], [6], [7]].

The combination of a radiotracer and a blue dye is the accepted gold standard for SLN mapping in vulvar cancer [8]. Nonetheless, its use in clinical practice is not straightforward, given that it requires planning in collaboration with a nuclear medicine unit and additional medical staff and has relatively high costs. These drawbacks have led to the testing of other tracers for SLN such as indocyanine green (ICG) and superparamagnetic iron oxide (SPIO) for the identification of SLNs in vulvar cancer [9,10].

Among these new tracers, SPIO has been widely demonstrated to be comparable to the standard radiotracer for breast and prostate cancer [[11], [12], [13], [14], [15]] but requires validation for vulvar cancer. SPIO is a non-radioactive tracer, which is an advantage for the patient and avoids the need for involvement of a nuclear medicine service. In 2019, the SARVU study, based on 20 women, found a SLN detection rate comparable to that with Tc-99 [16], although further data are needed to confirm this finding.

The objective of this study was to compare and validate SLN detection using SPIO compared to Tc99 in patients with vulvar cancer.