Comment on: Ultra-low dose superparamagnetic iron oxide nanoparticle injection for sentinel lymph node detection in breast cancer: prospective cohort study

Correspondence to: Yuzhou Zhu (e-mail: Zhuyuzhou@scu.edu.cn)

Colorectal Cancer Center

Department of General Surgery

West China Hospital, Sichuan University

No. 37 Guo Xue Street

Chengdu, 610041

Sichuan Province

China

BJS, https://doi.org/10.1093/bjs/znaf129, published 23 July 2025

We read with interest the study by Sundh et al.1, demonstrating that an ultra-low dose of superparamagnetic iron oxide (SPIO) achieves sentinel lymph node (SLN) detection rates comparable to technetium-99m/blue dye (Tc99m ± BD). We applaud their efforts; however, several points require further clarification.

First, the authors noted skin discoloration following injection. Given that baseline skin pigmentation varies substantially among ethnic groups, this could influence the visibility and extent of discoloration. Providing a breakdown by Fitzpatrick skin type or ancestry would help readers evaluate the generalizability of these findings.

Second, since skin discoloration was addressed, it is equally important to discuss safety monitoring. Even micro‑dose SPIO might transiently alter hematologic parameters or induce subclinical organ toxicity. Serial assessment of blood counts, inflammatory markers, and hepatic/renal function panels at baseline and during follow-up would further support the safety.

Third, the authors compared SLN detection rates among various hospitals and found no significant differences. The absence of comprehensive pairwise analyses among all centres may lead to premature conclusions of equivalence. We recommend conducting a complete pairwise analysis across all participating centres, applying appropriate multiple comparisons correction, and presenting detailed results to robustly confirm uniform performance.

We again commend Sundh et al. for their valuable contribution.