Skin-Staining From Superparamagnetic Iron Oxide (SPIO) for Sentinel Lymph Node Sampling-Follow-Up Results From a Randomized Trial.

BACKGROUND

SPIO is increasingly popular in sentinel lymph node biopsy (SLNBx) because of its non-radioactive nature and logistical advantage. Previous studies have demonstrated non-inferiority of SPIO compared to conventional dual tracer technique in SLNBx for early breast cancers. Brown stain from SPIO raises esthetic concerns in breast conservative treatment (BCT). The aim of this study is to compare the staining outcomes of SPIO to conventional blue dye.

METHOD: This is a prospective study reporting the predefined secondary analysis of our previously conducted randomized controlled trial (Trial registration number NCT05288686). SPIO arm patients were given subareolar SPIO injections before operation, and control arm patients received blue dye and radioisotope injections. Patients receiving BCT were selected and assessed at follow-ups for skin stains up to 18-month postoperatively.

RESULTS

One hundred and twelve patients and 113 SLNBx were included. Skin stains in both groups gradually decreased with time. SPIO group (61 SLNBx), as compared to control group (52 SLNBx), demonstrated larger incidence and size of skin stains throughout the study period (p < 0.001). The number of sentinel nodes (p = 0.03) and volume of lumpectomies (p = 0.034) were significantly correlated with skin stains at 18-month, that is, patients with more sentinel nodes harvested and larger volume of breast tissue resected have smaller stains by 18-month.

CONCLUSION

SPIO gives rise to higher incidence and larger skin stains compared to blue dye. Considerations should be given to cosmetic outcomes and shared decision-making be adopted whilst determining the optimal tracers in sentinel lymph node mapping.

TRIAL REGISTRATION: The original randomized controlled trial was registered on ClinicalTrials.gov (NCT05288686).