SLN (Sentinel Lymph Node) And Breast (cancer) Lymphoscintigraphy SLN (Sentinel Lymph Node) And Breast (cancer)

Flow – Primary Exam – defines the flow of the radiocolloid through the lymph chains which can reveal the following results Lymphedema Obstruction Leak Mapping – determines the following Solid Epithelial Tumors SLN Selective lymphad Enctomy

Early Lymphatic Research The following individuals were involved with initial lymphatic research 1653 T. Bartholin 1685-1770 H.F. LeDran 1890 Halstead

SLN - Breast The SLN was defined in breast cancer by the following individuals 1907 Jaimseon and Dobson 1960 Gould – “Sentinal Node” 1977 Cabanas 1977 Norton 1977 Ege

Selective Lymphadenectomy In the lymphatic system cancer spreads through the lymph chains and usually resides in what is known as the sentinel node. Removal of this node can result in the following: Improved Staging Decreased Surgical Morbidity Reduced Number Radical LN Dissections

The Concept Lymphatic spread of cancer is not only orderly, but also predictable The histological status of the SLN is predictive of the status of the distant Lymph node basin Skip metastases practically do not exist and metastatic spread can be discovered via the SLN

The above diagram shows the SLN which contains The cancerous cells. These cells then spread down The lymphatic channels to other lymph nodes (second, Third tiers)

Patient Population Early Breast Cancer will have the following Clinically Negative Axilla Tier 1 less than 2 cm 75% will be lymph node negative, beyond the SLN

Adjuvant Therapy Removal of the SLN

Lymphatic Anatomy Accompany blood supply Ectoderm : mammary gland is organ of skin - biologic unit Mammary lymph flow parallels lymph flow from skin

Lymphatic Anatomy Subcutaneous plexus : common drainage location does not predict basin Important for injection site

Radipharmaceuticals Visualize lymphatic channels from site of intestinal administration to first LN encountered Biologic Trap Active phagocytes by macrophages

Left – Red dots idenfity radiocolloid migrating into the afferent lymph from an intersitial injection where they are trapped by the macrophages Within the sinusoid spaces. Right – Magnification of a histoautoradiographh of the sentinel node Black dots show retention of the radioactive agent in the sinusoid spaces. Defines the ability to use radiocolloid to define the sentinel lymph node.

Radiopharmacenticals Particle size Number of Particles (few) Specific Activity (high) Decrease heating time Too much clumping of the particles occurs after two hours of preparation

Approximate Ranges of Particles Size For Various Radiocolloids Estimates Agent Concordant (nm) Other Median 99mTc-dextran 2-4   2 198Au-colloid 9-15 4-20/30 5-15 99mTc-antimony trisulfide 3-12/30 15-25 17-22 99mTc-sulfur colloid (prefiltered) 5/15-50 5-25 <30 99mTc-HSA- 4-100 5-80 99mTc-sulfur colloid (unfiltered) 15/50-5000 100/200-1000 100-600 Particle size varies in the different agents used for this procedure. The next side discusses ideal particle size.

Ideal Drug Radiocolloid between 100 – 200 nanometer This is not currently available Radiocolloid not used is: Tc 99m DTPA – mannosyl – dextrin Rapid clearance Low secondary LN accumulation

Preferred Radiocolloid Filtered Tc99m sulfur colloid Filter allows for particles that are < 30nm If unfiltered colloid is used the particles will not travel as well through the system It is also suggested that the colloid be no more than 2 hours post preparation

Tc99m sulfur colloid Not FDA approved Filtered : 220 nanometer 50 –200 nanometer particle Not considered the ideal agent because of its size

Technique Techniques that must be considered in this procedure are: Site of the injection – most important Volume – limited mL Dose – to be discussed Timing relative to surgery – after injecting the agent and imaging the SLN the patient must be sent to surgery for removal of the radioactive node

Site Types of injection that could be done Intratumeral : Not acceptable Peritumeral : IM LNs (not acceptable Intradermal – Subremal : Preferred The ideal injection is done just below skin which is then picked up by the lymphatic system Injections are done around the tumor site

ROI 1 – Shows the injection site ROI 2 – Indicates the flow of the colloid through the lymphatic channel ROI 3 – indicates the sentinel Node Graph displays the radiocolloid traveling through the lymphatic system over time.

This slide shows the difference between colloid size and its ability to flow through the infected system. Note that as the size of the particle increases, the amount of nodes that “light up” decrease. Hence, smaller colloid size is preferred when diagnosing disease.

Procedure 0.2 ml – preferred volume 0.5 mCi – dose Injection is done just underneath the skin with numerous injections around the tumor site, in a circular pattern Massage breast – after injection 90° Arm Abduction – location of arm Dynamic /Static – Dynamic process with static images are acquired ANT/LAO - images Mark patient – mark the SLN when it is identified 2 Hours – total time

Other Components Vital Dye – can also be used along with the radiocolloid Gamma probe – is used in the OR to determine which nodes are radioactive. Those that are are then removed

Success Rate Fraction of patients in whom this procedure has been preformed identify 97 – 99% of the SNL False Negative : 1 – 4%

Cases

These images illustrate variable patterns of lymphatic drainage These images illustrate variable patterns of lymphatic drainage. Imaging times occurred between 31 to 60 min post intradermal injection of 99mTc‑HSA nanocolloid (A) RAO view shows single lymphatic vessel leading to single sentinel lymph node, with serial visualization of subsequent tier nodes (B) LAO view shows 2 separate lymphatics leading through widely diverging pathways, to 2 separate but adjacent sentinel node and tier nodes (C) LAO view shows 3 separate lymphatics leading, through widely diverging pathways (D) RAO view shows multiple lymphatics leading from site of infection in outer upper quadrant to at least 3 separate sentinel nodes and subsequent tier nodes

This procedure done at UofL Hospital shows: The injection site covered with a lead shield Over time the lymph chain is noted Sentinel node is defined

The first image (L) shows the injection site that is located POST. Because of the excessive activity this injection site it can be seen in the ANT image. Note that slightly distal from the injection site the SNL. Imaging is improved when (second image): A) the injection site is extracts; and B) A transmission image is take with the Co-57 flood. In the last image (R) a transmission scan is done in the groin region to assure that there is no additional SNL.

Melanoma Upper Back 40 year old male presented with superficial spreading malignant melanoma of the left upper back. On dynamic images there is tracer uptake inferior and lateral to the melanoma site. The intense focus is activity at the injection sites around the melanoma Posterior Projection

Melanoma Upper Back (Cont) Image on the left includes activity from a transmission source which helps to outline the body. There are 3 discrete foci of tracer uptake (shown by arrows) anterior, inferior and lateral to the injection sites (shown by arrowhead). Micrometatses were found in one of the marked lesions. Anterior Projection Static Images

Melanoma Left Cheek A lateral static image from patient who had a left cheek melanoma (arrowhead shows sites of injection) demonstrates tracer uptake in the submandibular and posterior cervical lymph nodes (shown by arrows).

Pre-Operative Lymphatic Mapping Breast Cancer Cancer was on the lower side of the breast and was injected with the radiocolloid (the dark black area on the bottom of the breast). You can easily see that there are two lymphatics which leave the breast (labeled with blue L) and go to two distinct sentinel lymph nodes (SLN).

The picture on the left shows a sentinel lymph node (N) which is tinted blue because it has taken up the blue dye which was injected around the breast cancer. The blue dye got there by traveling through the lymphatics which leave the breast and connect to the SLN. This picture shows the lymphatic vessel (L) with blue dye in it. Mapping

Breast Lymphoscintigraphy Mapping of the breast is done in order to surgically remove the SLN This can be done with blue dye This can be done with radiocolloid and a gamma knife Usually both are done at the same time

Other Applications This procedure may also be useful with the following cancers Malignant melanoma Breast CA Cervical CA/Vulval CA Colorectal CA Head and Neck CA Thyroid CA Gastrial/Esophageal CA Penile CA