Sentinel lymph node scintigraphy: a new radionuclide imaging technique used at Almazov Centre

Scintigraphy is a medical imaging technique wherein radioisotopes are injected and the emitted radiation is captured to create images.

“Recently, we have started using sentinel lymph node scintigraphy in women with early-stage breast cancer. Locating sentinel lymph nodes and lymphatic drainage pathways in early breast cancer makes it possible to perform a sentinel node biopsy in these patients and further determine the tactics of treatment and the extent of surgery. Detected sentinel lymph nodes after intraoperative biopsy are sent for urgent histological examination in order to exclude metastasis. The absence of metastases will allow performing an organ-preserving surgery without axillary lymphadenectomy, which, unfortunately, has to be performed in the surgical treatment of this disease, without knowledge of the degree of involvement of the lymphatic system,” explains Prof. Darya Ryzhkova, Chief Researcher of the Department of Nuclear Medicine and Theranostics

The radiopharmaceutical used for sentinel lymph node scintigraphy is 99mTc-Technefit, which is also used for liver and spleen scintigraphy as well as lymphoscintigraphy of the upper and lower extremities. This is a Technetium-99m-labeled colloid. The colloidal particles are of a very small diameter, allowing its use for sentinel lymph node scintigraphy. When intradermal, subcutaneous or peritumoral injection is performed, the isotope-labeled colloidal particles penetrate the lymphatic nodes through the lymphatic vessels and settle there. The first lymph node that accumulates the radiopharmaceutical along the lymphatic outflow from the breast tumor is the sentinel node.

Scintigraphy and SPECT (single-photon emission computed tomography) of sentinel lymph nodes

 

“The sentinel lymph node, which is the first to capture radio-labeled colloidal particles in the lymphatic outflow from a breast tumor, is also the first to encounter metastatic tumor cells. This lymph node is removed during intraoperative biopsy of the sentinel lymph nodes. Then, the removed material is sent to the pathology department for examination after a preliminary measurement of its radioactivity, which is usually below the minimum significant level,” comments Olga Yudina, Head of the Radiology Department of Almazov Centre.

The pathology department performs an urgent histological examination of the lymph node and the edges of the resection of the mammary gland.

“Our task is to do this examination as quickly as possible and give the results to our colleagues in the OR in 20 minutes. The absence of damage to the studied lymph nodes allows us to conclude that the patient does not have metastases in the axillary lymph nodes. This makes it possible to minimize the intervention in the axillary area by removing only one or a few lymph nodes that were detected during scintigraphy due to the accumulation of a radiopharmaceutical in them,” comments Lyubov Mitrofanova, Chief Researcher of the Pathology Unit.

The use of this radionuclide imaging technique and subsequent surgical treatment became possible due to the availability of an intraoperative gamma probe at Almazov Centre. The device detects radiation with high accuracy and helps the surgeon find and remove sentinel lymph nodes.

A gamma probe is used during surgery to pinpoint sentinel lymph nodes: it supports the detection procedure by emitting acoustic signals and displaying the digital value of the pulse on the screen. The ultra-sensitive sensor allows locating the sentinel lymph node with minimal trauma to the surrounding tissues. The advantages of this device over other widely used hand-held gamma detectors are its higher sensitivity and specificity. The required lymph node is detected with greater accuracy, minimum surgical trauma and radiation exposure.

“This technique provides the most precise localization of sentinel lymph nodes in tumors of any location, and the available laparoscopic gamma probe allows for a minimally invasive approach,” explains Dr. Alexander Shemerovsky, oncologist and surgeon.

The surgical stage of treatment comes the next day after scintigraphy. A small dose of the radiopharmaceutical injected locally into the area of the affected mammary gland is sufficient to detect the sentinel lymph nodes and allows for a low level of radiation exposure of the patient and medical personnel.

This integrated approach to the diagnosis and treatment of early stage breast cancer has become part of the practice at Almazov Centre and it gives women the opportunity to recover and live a full life after the treatment.