Sentinel lymph node detection in early-stage breast cancer - Are technetium-99m-nanocolloid and superparamagnetic iron oxide diagnostically equivalent procedures? A propensity score matched real world data analysis

Several studies have compared validated tracers, such as the radioactive tracer technetium-99m nanocolloid (99mTc-nanocolloid) and superparamagnetic iron oxide (SPIO), for sentinel node biopsy (SNB) in early-stage breast cancer (eBC). These studies mostly investigated the differences in detection rate and SNB-related adverse events. The aim of our study was to determine whether there are any crucial differences between the two procedures, including the duration of surgery and the number of detected sentinel lymph nodes (SN), which may affect patient treatment and the standard of care in eBC. All patients were treated at the University Medical Centre Mainz by certified breast surgeons. Two consecutive groups of patients were identified based on the injected tracer: Technetium Group (N = 517), patients treated from January 1, 2017 to December 31, 2019, with 99mTc-nanocolloid as tracer and SPIO Group (N = 456), patients treated from January 1, 2020 to December 31, 2022, with superparamagnetic iron oxide particles as ferromagnetic tracer. To avoid potential bias, we performed propensity score matching. After performing propensity score matching, the total surgery time was significantly shorter in the Technetium Group compared to the SPIO Group [64 (48 - 84) vs. 71.5 (58 - 98) minutes; p < 0.001]. Both groups did not differ regarding detection rates, or complications (p > 0.05). The median number of removed SN was 1.0 in the 99mTc-nanocolloid Group and 2.0 in the SPIO Group. In conclusion, our analysis showed that the use of 99mTc- nanocolloid for SNB resulted in shorter operation time and removal of less SN compared to the SPIO intervention.