Selective internal radiation therapy
Overview
 
Selective internal radiation therapy (SIRT) is a form of radiation therapy
Radiation therapy
Radiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...

 used to treat cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

. It is generally for selected patients with unresectable cancers, those that cannot be treated surgically
Surgical oncology
Surgical oncology is the branch of surgery which focuses on the surgical management of cancer.The specialty of surgical oncology has evolved in steps similar to medical oncology, which grew out of hematology, and radiation oncology, which grew out of radiology...

, especially hepatic cell carcinoma
Hepatocellular carcinoma
Hepatocellular carcinoma is the most common type of liver cancer. Most cases of HCC are secondary to either a viral hepatitide infection or cirrhosis .Compared to other cancers, HCC is quite a rare tumor in the United States...

 or metastasis
Metastasis
Metastasis, or metastatic disease , is the spread of a disease from one organ or part to another non-adjacent organ or part. It was previously thought that only malignant tumor cells and infections have the capacity to metastasize; however, this is being reconsidered due to new research...

 to the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

. The treatment involves injecting tiny microspheres of radioactive
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

 material into the arteries
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....

 that supply the tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...

.

The microspheres themselves are made of glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

 or resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...

. The resin material tends to embolize
Embolism
In medicine, an embolism is the event of lodging of an embolus into a narrow capillary vessel of an arterial bed which causes a blockage in a distant part of the body.Embolization is...

 more easily and thus can be used to stop blood supply to the tumors.
Encyclopedia
Selective internal radiation therapy (SIRT) is a form of radiation therapy
Radiation therapy
Radiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...

 used to treat cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

. It is generally for selected patients with unresectable cancers, those that cannot be treated surgically
Surgical oncology
Surgical oncology is the branch of surgery which focuses on the surgical management of cancer.The specialty of surgical oncology has evolved in steps similar to medical oncology, which grew out of hematology, and radiation oncology, which grew out of radiology...

, especially hepatic cell carcinoma
Hepatocellular carcinoma
Hepatocellular carcinoma is the most common type of liver cancer. Most cases of HCC are secondary to either a viral hepatitide infection or cirrhosis .Compared to other cancers, HCC is quite a rare tumor in the United States...

 or metastasis
Metastasis
Metastasis, or metastatic disease , is the spread of a disease from one organ or part to another non-adjacent organ or part. It was previously thought that only malignant tumor cells and infections have the capacity to metastasize; however, this is being reconsidered due to new research...

 to the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

. The treatment involves injecting tiny microspheres of radioactive
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

 material into the arteries
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....

 that supply the tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...

.

The microspheres themselves are made of glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

 or resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...

. The resin material tends to embolize
Embolism
In medicine, an embolism is the event of lodging of an embolus into a narrow capillary vessel of an arterial bed which causes a blockage in a distant part of the body.Embolization is...

 more easily and thus can be used to stop blood supply to the tumors. Inside the microsphere is the isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

 yttrium-90
Isotopes of yttrium
Natural yttrium is composed of only one isotope 89Y. The most stable radioisotopes are 88Y which has a half-life of 106.65 days and 91Y with a half-life of 58.51 days. All the other isotopes have half-lives of less than a day, except 87Y, which has a half-life of 79.8 hours, and 90Y, with 64 hours...

, which has beta-emission
Beta particle
Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay...

 with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 of 2.6 days. Currently there are 2 types of microspheres: TheraSphere
TheraSphere
TheraSphere is a hepatocellular carcinoma treatment therapy that consists of millions of microscopic, radioactive glass microspheres being infused into the arteries that feed liver tumors. These microspheres then embolize, lodging themselves in the liver's capillaries and bathing the malignancy...

 and SIR-Spheres
SIR-Spheres
SIR-Spheres microspheres is used to treat patients with unresectable liver cancer. These are mostly patients with hepatocellular carcinoma , metastatic colorectal cancer , or metastatic neuroendocrine tumours...

, which differ in their radioactivity per sphere and embolic effect. SIR-Spheres have more embolic effect and less activity per sphere. This makes them better for certain cancers such as neuroendocrine tumors
Neuroendocrine tumors
Neuroendocrine tumors are neoplasms that arise from cells of the endocrine and nervous systems. Many are benign, while some are cancers...

, which are highly vascular.

Before a patient can have the SIRT treatment, the patient must have a hepatic angiogram
Angiogram
Angiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins and the heart chambers...

, a technetium macroaggregated albumin scan (a radiopharmacological lung scan), and CT scan
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...

. The angiogram defines the arterial anatomy and helps the interventional radiologist
Interventional radiology
Interventional radiology is a specialty of radiology, in which image-guided procedures are used to diagnose and treat a multitude of diseases across all body systems...

 embolize certain arteries that might carry the microspheres away from the target location to the gastrointestinal system
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....

 or lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

s. Technetium is used to measure lung shunting. Higher lung shunting means increased likelihood of the radioactive particles traveling to the lung and doing damage there. Patients exceeding 20% are usually excluded from this treatment because of the dangers of radiation pneumonitis
Pneumonitis
Pneumonitis or pulmonitis is a general term that refers to inflammation of lung tissue.Pneumonia is pneumonitis combined with consolidation and exudation...

. CT measures the tumor size to help determine the correct dosage
Dosing
Dosing generally applies to feeding chemicals or medicines in small quantities into a process fluid or to a living being at intervals or to atmosphere at intervals to give sufficient time for the chemical or medicine to react or show the results....

 of microspheres.

Most patients have lethargy, anorexia
Anorexia (symptom)
Anorexia is the decreased sensation of appetite...

, and nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

 after the surgery. Ten percent have gastric ulcerations
Peptic ulcer
A peptic ulcer, also known as PUD or peptic ulcer disease, is the most common ulcer of an area of the gastrointestinal tract that is usually acidic and thus extremely painful. It is defined as mucosal erosions equal to or greater than 0.5 cm...

 because the microspheres have moved into the arteries that supply the GI tract. The interventional radiologist tries to prevent this by blocking the common hepatic artery
Common hepatic artery
In anatomy, the common hepatic artery is a short blood vessel that supplies oxygenated blood to the liver, pylorus , duodenum and pancreas....

.

After microspheres are injected, they can be confirmed with a Bremsstrahlung image, which uses a gamma camera
Gamma camera
A gamma camera, also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy...

 to catch the gamma radiation
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...

 from the yttrium-90. A PET scan
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...

 is then done weeks later to monitor the tumor progression. Most patients have some response to the treatment, but about one third do not respond to this treatment.

Use, trials and approvals

A phase III trial (SIRT versus sorafenib) is in progress. As of mid 2010 it was not recommended by NICE
NICE
NICE may refer to:* National Independent Cadres and Elites in Iraq* National Institute for Coordinated Experiments, a fictional organisation in C.S...

.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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