Purpose: To evaluate the detection rate of sentinel lymph node (SLN) mapping in early-stage ovarian cancer using [99mTc]Tc-nanocolloid and indocyanine green (ICG), and the added value of an intraoperative gamma camera.
Methods: This was a prospective single-center trial of 63 patients with suspected early-stage epithelial ovarian cancer who underwent SLN mapping with combined tracers. [99mTc]Tc-nanocolloid was injected into the ovarian ligaments before adnexectomy, and if malignancy was confirmed on intraoperative frozen section, ICG was administered after adnexectomy in immediate staging cases. SLNs were identified using a handheld gamma probe, the gold standard, and a portable gamma camera for radiotracer localization, alongside near-infrared imaging for ICG. We calculated SLN detection rates for each tracer and concordance between the tracers (reflecting the impact of injection timing), including identification of the same SLN- as well as between detection modalities. Cohen’s κ and PABAK were used to assess concordance between detection modalities. Patients with confirmed malignancy underwent complete pelvic and aortic lymphadenectomy.
Results: Among 63 patients, sentinel lymph nodes (SLNs) were detected in 79.4% using [99mTc]Tc-nanocolloid. In the 30 patients who also received ICG, the combined use of both tracers achieved a detection rate of 93.3%, with higher detection in the aortic region compared to the pelvic region (83.3% vs. 43.3%). The intraoperative gamma camera showed 83.3% concordance with the gamma probe, including 87.5% concordance in the aortic region and 66.7% in the pelvic region. Among patients who received both tracers, 14 had drainage in at least one region by both, and 12 of these (85.7%) showed concordant detection of the same SLN. Concordance was 100% in re-staging and 77.8% in immediate surgeries.
Conclusion: SLN mapping in ovarian cancer using a dual tracer approach is feasible and yields a higher detection rate than single tracers. The gamma camera identified SLN localization mainly in aortic regions. This combination may improve nodal staging in early ovarian cancer and reduce the need for systematic lymphadenectomy. Post-adnexectomy injection is a practical alternative to injection before adnexectomy for immediate surgeries, although caution is needed due to potential variations in lymphatic drainage.
