A delayed sentinel lymph node biopsy is a procedure that allows the surgeon to perform surgery to stage the axilla only when it is truly necessary. It provides an opportunity for up to 80% of high-risk DCIS patients to protect lymph nodes that do not need to be removed.

What is a Sentinel Lymph Node Biopsy?
A sentinel lymph node biopsy is the most common cancer staging process for patients with high-risk DCIS.

The breast drains through lymphatic vessels that lead to lymph nodes in the axilla (under the arm). The first lymph nodes to receive fluid from the breast are called the sentinel lymph nodes. If an invasive breast cancer spreads to the lymph nodes, it will first go to these sentinel nodes.

During a sentinel lymph node biopsy, the breast is injected with a magnetic tracer, blue dye, radioactive tracer or combination of the three. The lymphatic vessels in the breast pick up the tracer/s and take them to the first draining lymph nodes in the axilla (the sentinel nodes). This process helps the surgeon identify the most likely lymph nodes to be affected if an invasive breast cancer has spread. This information is important for breast cancer staging and future treatment decisions.

Issues with this procedure
While sentinel lymph node biopsy has reduced the amount of initial surgery for patients compared to the former standard of early cancer care – axillary lymph node dissection, where all lymph nodes are removed from the underarm – it may still represent overtreatment in cases of non-invasive breast cancer (DCIS).

The common practice is to perform a sentinel lymph node biopsy at the time of a mastectomy for DCIS. This is done as a precaution in case invasive cancer is discovered in the breast, because marking of the sentinel nodes is not possible after mastectomy due to the pathways for the tracer being removed with the breast.

However, this means that patients who do not have invasive cancer found in the breast will have sentinel nodes removed unnecessarily. Recent research shows that this may be the case for up to 80% of patients.

Removing sentinel nodes can cause life-long complications such as lymphedema, with symptoms including swelling, arm stiffness, numbness, and pain. The delayed sentinel lymph node procedure offers a way to avoid this.

What is delayed sentinel lymph node biopsy?
A delayed sentinel lymph node biopsy allows the surgeon to only remove lymph nodes when it is really necessary.

Rather than doing a sentinel lymph node biopsy on all patients undergoing mastectomy for DCIS, the sentinel nodes are marked with a magnetic tracer (superparamagnetic iron oxide) that is injected into the breast prior to the surgery. This tracer drains to the lymph nodes and remains there for 30 days, providing a detectable signal for the surgeon to locate the nodes, if needed.

The breast tissue will then be sent to pathology to analyze. If invasive cancer is present, the patient can return for a sentinel lymph node biopsy, weeks after the initial surgery. This procedure is known as a delayed sentinel lymph node biopsy. Importantly, if no invasive cancer is found, as will be the case for most patients, the nodes can be left alone.

Delayed sentinel lymph node biopsy allows surgeons to have more time to make well-informed decisions about the best way to treat their patients and provides DCIS patients the opportunity to reduce the physical impact and risks of unnecessary surgery.

References:
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 [published online ahead of print, 2023 Jan 31]. Ann Surg Oncol. 2023;10.1245/s10434-022-13064-0. doi:10.1245/s10434-022-13064-0.