Use of superparamagnetic iron oxide for sentinel lymph node detection following neoadjuvant systemic therapy. A systematic review and meta-analysis

Superparamagnetic iron oxide(SPIO) is used increasingly in sentinel lymph node(SLN) identification in breast cancer patients. Identification ratios in the upfront setting are comparable to that of radioisotope and blue dye(RI/BD). However, its use in the neoadjuvant(NACT) setting remains under debate. The aim of this study was to assess the outcomes of SPIO in breast cancer patients receiving NACT followed by surgery. A systematic review of major databases was performed. Studies examining SPIO compared to standard of care(RI/BD) for SLN detection after NACT were included. Primary outcomes included individual detection rate(nodal detection) and nodal detection rate (number of nodes detected). Trial Sequential Analysis (TSA) was performed to assess results certainty. Study quality was assessed using the MINORS tool for observational studies. Five studies involving 374 patients were included. Regarding individual detection rate, SPIO was successful in 308/314 patients and RI in 297/314 patients. Pooled individual detection rates for SPIO and RI were 98.1 % vs 94.6 %(weighted Risk Ratio 1.02,95 % CI 0.99,1.05,p = 0.18; I² = 24.3 %). Four studies examined nodal detection rates. Within these studies, a total of 625 SLNs were retrieved with 569 detected with SPIO and 468 with RI(mean: 2.26 SLN for SPIO and 1.86 for RI) with a respective nodal detection rate of 91.0 % vs 74.9 %(weighted Risk Ratio:1.25,95 % CI 1.06,1.47,p < 0.001; I² = 89.6). The median MINORS score was 19/24(range 14–24), denoting good quality. In patients treated with NACT, SPIO performed comparably to RI, but seems to identify more SLNs. Routine use of SPIO in the neoadjuvant setting should be considered safe and effective.