Superparamagnetic Iron Oxide Used Alone Is Non-Inferior to the Combination of Radioactive Tracer and Superparamagnetic Iron Oxide in Detecting Sentinel Lymph Nodes in Early-Stage Vulvar Cancer.

Background: Radioactive colloids are considered the standard of care for sentinel lymph node (SLN) detection. An alternative detection method using superparamagnetic iron oxide (SPIO) nanoparticles is well documented in breast cancer but poorly studied for gynecological tumors, including vulvar cancer (VC). Objective: Our aim was to evaluate the feasibility, accuracy, and safety of SPIO nanoparticles for SLN mapping in patients with VC as a stand-alone technique compared with the combination of two methods: the standard of care using a radioactive isotope (technetium-99; Tc-99) and SPIO as a new tracer. Methods: We conducted a prospective and observational study of SLN mapping in patients with stage IB VC and tumor size ≤ 4 cm. We calculated detection and malignancy rates per patient and per groin in both study groups. During the 36-month follow-up, the groin recurrence rate was estimated for positive and negative SLNs. Kaplan-Meyer curves were used to analyze the probability of survival, depending on disease-free survival. Results: A total of 110 groins assessed by SLN in 60 patients included in this study were analyzed (70 groins from 40 patients in the group with a single tracer and 40 groins from 20 patients in the group of combined tracers). At least one sentinel lymph node was detected in every patient while the bilateral detection rate was 92.3% for the SPIO group and 88.2% for the Tc-99 and SPIO group. The groin detection rate was 94.3% and 90%, respectively. SLN mapping failure was similar in both groups (2.8% and 2.5%, respectively). During a 3-year follow-up, the isolated groin recurrence rate was 2.1% for negative groins and for disease-free survival it was 28.9 months in the combined tracer group versus 32.8 months in the SPIO group. The Kaplan-Meyer curves showed the increased probability of survival for the SPIO group (87.5%); however, it was insignificant. Conclusions: SLN mapping using the SPIO technique in patients with VC is non-inferior to the combined SPIO and Tc-99 method.