Sentinel Lymph Node Biopsy in Ductal Cancer in Situ or Unclear Lesions of the Breast and How to Not do it. An Open-label, Phase 3, Randomised Controlled Trial. (SentiNot 2.0).

The SentiNot 2.0 protocol aims to elucidate the effectivity and accuracy of the delayed sentinel lymph node dissection concept (dSLND) when upfront SLND is considered unnecessary, such as in the setting of a preoperative diagnosis of DCIS, in cases of unclear BIRADS 4 or 5 lesions that are planned for diagnostic excisional biopsy or in selected cases of risk reducing mastectomy. Acknowledging the large variance of practice in this setting, the study aims to address pragmatism to allow for inclusion. For this reason, the trial is designed separately and independently for mastectomy and breast conserving surgery, so that participating sites can recruit as fitting in their practice.

In patients included in the SentiNot 2.0 trial, SPIO (MagTrace,2.0 ml) is injected up to 24 hours preoperatively or perioperatively during primary breast surgery on patients with a preoperative diagnosis of DCIS (or suspicious lesions with no clear diagnosis of invasive cancer but, considered for SLND). The SPIO is injected close to the lesion. If injected less than 24 hours before the operation, a 5 minute massage should be performed. Planned breast surgery is performed. The transcutaneous magnetic counts by SentiMag in the axilla is measured at the end of the breast procedure, so as to allow for confirmation that SLND may be identified. Thus,the SLN is consequently marked with SPIO, but not excised.

In this manner, women that have pure DCIS on final histopathological examination have avoided unnecessary upfront SLND.

If there is underlying invasive breast cancer on final histopathological examination, SLND will be performed at a second operation (d-SLND). A preoperative injection of radioisotope (RI) RI will be added to maximize the chance to detect the SLN. SLND will start with a registration of the magnetic and isotope signal in the axilla, and the incision will be placed in relation to the signal. In patients that have undergone mastectomy, tracers are to be injected intracutaneously in the lateral part of the mastectomy scar. The routine use of blue dye (BD) is strongly advised, but is not compulsory. However, if no transcutaneous signal for SPIO and RI is measured in the axilla pre-incision, an injection of BD according local routines will be administered. Subsequently, SLND will be performed. Patients with upgrade to invasive cancer will undergo SLND, but will be randomized with an allocation ratio of 1:1 to SentiMag first or Radioactive probe first. This will mandate the "principal modality" to perform SLND. Every step of the procedure will be controlled; if the principal modality fails, then the surgeon will use the "secondary". If the principal modality succeeds, the secondary will be registered and documented.

The procedure will be divided to the following steps: