99mTc-Sulfur Colloid is a radiopharmaceutical agent used in nuclear medicine for lymphoscintigraphy. It is composed of technetium-99m (99mTc) labeled sulfur particles suspended in a colloidal solution.
When injected into the body, 99mTc-Sulfur Colloid is taken up by the lymphatic system and allows for the visualization of lymphatic drainage patterns. This is particularly useful in the staging and management of certain cancers, such as melanoma and breast cancer, where the spread of tumors through the lymphatic system needs to be monitored.
The particles in 99mTc-Sulfur Colloid are small enough to be carried by lymphatic fluid, but large enough to be trapped in lymph nodes. This selective uptake allows for the identification and mapping of lymph nodes that may be affected by cancer metastasis.
Overall, 99mTc-Sulfur Colloid plays a crucial role in the diagnosis and management of cancer by providing valuable information on lymphatic drainage pathways and lymph node involvement. It is a safe and effective imaging agent that has been widely used in clinical practice for decades.
Description
99mTc-Sulfur Colloid (99mTc-SC) or 99mTc-Rhenium Sulfur Colloids (99mTc-RSC) or 99mTc-Tin Sulfur Colloids (99mTc Stannous Colloid, 99mTc-TSC) are suspensions of particles used in lymphoscintigraphy. Particle size is very important as too small particles migrate too fast and too large particles remain in the original injection site for too long. Average particle size is between 100 nm and 1 µm but the ideal seems to be 100–300 nm.
Clinical applications
99mTc-Sulfur Colloid is the agent most commonly used for sentinel node localization. This tracer is indicated to assist in the localization of lymph nodes draining a primary tumor in patients with breast cancer or malignant melanoma and the modality makes use of a hand-held gamma counter for localization. Sulfur colloids are also used in the imaging areas of functioning reticuloendothelial cells in the liver, spleen and bone marrow, in the studies of esophageal transit and gastroesophageal reflux, and detection of pulmonary aspiration of gastric contents. It is also used as an aid in the evaluation of peritoneo- venous (LeVeen) shunt patency. The product can be used sc (lymphoscintigraphy), ip, iv or po (esophageal transit and gastroesophageal reflux). The dose per patient is in the range of 0.5–5 mCi.
Availability
- 99mTc-Sulfur Colloids are available from BRIT (TCK-5), Pars Isotope (SulfurColloid), Pharmalucence (Sulfur Colloid injection), Sun Pharmaceuticals.
- 99mTc-Rhenium Sulfur Colloids are available from IBA Molecular (Curium) (Nanocis; marketed since 1981) or GE Healthcare (Nanocoll; EU MA 1995; discontinued).
- 99mTc-Stannous Colloids are available from GE Healthcare (Amerscan Hepatate II®, licensed to Mediam Pharma), Medi-Radiopharma (Res-Scint), Nihon Medi-Physics (Tin Colloid kit), POLATOM (PoltechColloid).
- 99mTc-Rhenium Sulfur Colloids are available from IBA Molecular (Curium) (Nanocis; marketed since 1981) or GE Healthcare (Nanocoll; EU MA 1995; discontinued).
Products such as AN-Sulfur Colloid (Pharmalucence), Sulfur Colloid (GE Healthcare, discontinued 2002), Technecoll (Mallinckrodt) and Tesuloid (Bracco) have been discontinued.
In 2020 in the USA, the list price of a kit of Sulfur Colloid is around US$ 275.
Competition
There are now several products available for lymphoscintigraphy (99mTc-radiolabeled human albumin particles). 99mTc-Antimony triSulfide colloid was previously one of the agents of choice, but this agent is no longer commercially available, except in Australia and New Zealand.
Since 2013, the proprietary tracer 99mTc-Tilmanocept (Lymphoseek) from Navidea (now Cardinal Health) is also available for lymphoscintigraphy.
Comments
There is no standardized technique for sentinel node localization. Wide variations exist regarding particle size, timing of injection, volume and placement of the injection, use of pre-operative imaging, and operative techniques. Therefore, although the technology is widely used mainly for breast cancer, and very efficient to reduce the occurrence of metastasized disease, applications and protocols are linked to local habits. Each hospital uses a product (albumin, sulfur colloids) and improved techniques (timing injection sites, doses), that actually lead to the same positive results.
In 2013, Navidea launched the proprietary tracer, 99mTc-Tilmanocept (Lymphoseek). In October 2014, the FDA recognized 99mTc-Tilmanocept as the new Golden Standard for sentinel node detection. This could probably result in the short-term disappearance (at least strong reduction) from the market of all other generic tracers sold for this indication, but the price difference remains in favor of colloids.