Delayed Sentinel Lymph Node Dissection in Patients with a Preoperative Diagnosis of Ductal Cancer In Situ by Preoperative Injection with Superparamagnetic Iron Oxide (SPIO) Nanoparticles: The SentiNot Study

Karakatsanis, A., Eriksson, S., Pistiolis, L. et al. Delayed Sentinel Lymph Node Dissection in Patients with a Preoperative Diagnosis of Ductal Cancer In Situ by Preoperative Injection with Superparamagnetic Iron Oxide (SPIO) Nanoparticles: The SentiNot Study. Ann Surg Oncol 30, 4064–4072 (2023). https://doi.org/10.1245/s10434-022-13064-0

The upgrade rate of DCIS to invasive cancer is variably quoted at ~25%, and many of these patients will therefore require SLNB. Whilst in the mastectomy setting, SLNB is often performed at the time of mastectomy, in women undergoing breast conservation, SLNB is not performed upfront, so many of these women will require a second surgery.

SLNB is associated with side effects such as lymphoedema, cording, shoulder stiffness and chronic pain and whilst rates are not high, SLNB should be avoided if not required. The rationale for upfront SLNB after mastectomy is based on lymphatic disruption making subsequent SLNB tracer injection impossible. This may also happen in cases where a major breast reshaping is performed via therapeutic mammoplasty.

The SentiNOT trial set out to evaluate use of a long acting SLNB tracer, SupraParamagnetic Iron Oxide (SPIO), to avoid unnecessary SLNB in these patients.

The study was a  prospective observational cohort study of women with DCIS who either had mastectomy (regardless of tumour stage and type), or breast conservation surgery if they had higher risk DCIS with a greater upgrade risk (T2, grade 3 or mass forming DCIS). During primary surgery, no SLNB was performed but SPIO was injected.  If they upgraded to invasive disease, a SLNB was performed with SPIO and isotope +/- blue dye.  

In the cohort of 254 women, 31% had simple WLE, 32% had oncoplastic conservation and 36% had mastectomy. The upgrade rate also varied, as expected, by type of surgery with 24% upgrading after simple conservation, 41% after oncoplastic conservation and 38% after mastectomy.  

After a median of 28 days (range 9-46) the SPIO was more reliable than isotope at node identification with 98% versus 64% SLNB identification (if blue dye was also used, less if not). Only 27.9% of SLNs were concordant for SPIO and isotope. The results were affected by breast surgery type. In women having a simple conservation SPIO and isotope both gave 100 identification rates for the sentinel node.  In contrast, after therapeutic mammoplasty, rates were 100% for SPIO but only 33% for isotope. After mastectomy, the rate was 80% for SPIO and only 45% for isotope.

SPIO was found to be cost effective.  

They conclude that use of SPIO for delayed SLNB may avoid over treatment of the axilla in women with DCIS, especially following mastectomy or complex oncoplastic procedures.

Limitations are the length or time between first and second surgery. This was a median of 28 days, but as little as 9 days. They do not report any data on variation in SPIO efficacy with time, which would be very useful data to have in clinical practice and whether any degradation in efficacy maybe compensated for by dose adjustment.

Summary Author: Professor Lynda Wyld: Professor of Surgical Oncology, University of Sheffield, Consultant Oncoplastic Breast Surgeon, Doncaster and Bassetlaw Teaching Hospitals.