Radionuclide therapy (RNT, also known as unsealed source radiotherapy or molecular radiotherapy) uses

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

substances called

radiopharmaceutical Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes. Radiopharmaceuticals can be used as diagnostic and therapeutic agents. Radiopharmaceuticals emit radiation themselves, which ...

s to treat medical conditions, particularly

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

. These are introduced into the body by various means (

injection Injection or injected may refer to: Science and technology * Injective function, a mathematical function mapping distinct arguments to distinct values * Injection (medicine), insertion of liquid into the body with a syringe * Injection, in broadca ...

ingestion Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in a substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms, inge ...

are the two most commonplace) and localise to specific locations,

organs In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to a ...

or tissues depending on their properties and administration routes. This includes anything from a simple compound such as

sodium iodide Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na+) and iodide anions ...

that locates to the

thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by ...

via trapping the iodide ion, to complex biopharmaceuticals such as recombinant antibodies which are attached to radionuclides and seek out specific

antigens In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. An ...

on cell surfaces. This is a type of targeted therapy which uses the physical, chemical and biological properties of the radiopharmaceutical to target areas of the body for radiation treatment. The related diagnostic modality of

nuclear medicine Nuclear medicine (nuclear radiology, nucleology), is a medical specialty involving the application of radioactivity, radioactive substances in the diagnosis and treatment of disease. Nuclear imaging is, in a sense, ''radiology done inside out'', ...

employs the same principles but uses different types or quantities of radiopharmaceuticals in order to

image An image or picture is a visual representation. An image can be Two-dimensional space, two-dimensional, such as a drawing, painting, or photograph, or Three-dimensional space, three-dimensional, such as a carving or sculpture. Images may be di ...

or analyse functional systems within the patient. RNT contrasts with sealed-source therapy (

brachytherapy Brachytherapy is a form of radiation therapy where a sealed radiation, radiation source is placed inside or next to the area requiring treatment. The word "brachytherapy" comes from the Ancient Greek, Greek word , meaning "short-distance" or "s ...

) where the radionuclide remains in a capsule or metal wire during treatment and needs to be physically placed precisely at the treatment position. When the radionuclides are

ligands In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ...

(such as with Lutathera and Pluvicto), the technique is also known as radioligand therapy.

Clinical use

Thyroid conditions

Iodine-131 Iodine-131 (131I, I-131) is an important radioisotope of iodine discovered by Glenn Seaborg and John Livingood in 1938 at the University of California, Berkeley. It has a radioactive decay half-life of about eight days. It is associated with nu ...

(¹³¹I) is the most common RNT worldwide and uses the simple compound

with a radioactive isotope of

iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...

. The patient (human or animal) may ingest an oral solid or liquid amount or receive an intravenous injection of a solution of the compound. The iodide ion is selectively taken up by the

gland. Both benign conditions like

thyrotoxicosis Hyperthyroidism is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...

and certain malignant conditions like

papillary thyroid cancer Papillary thyroid cancer (papillary thyroid carcinoma, PTC) is the most common type of thyroid cancer, representing 75 percent to 85 percent of all thyroid cancer cases.Chapter 20 in: 8th edition. It occurs more frequently in women and presents ...

can be treated with the radiation emitted by

radioiodine There are 40 known isotopes of iodine (53I) from 108I to 147I; all undergo radioactive decay except 127I, which is stable. Iodine is thus a monoisotopic element. Its longest-lived radioactive isotope, 129I, has a half-life of 16.14 million ye ...

. Iodine-131 produces

beta Beta (, ; uppercase , lowercase , or cursive ; or ) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Ancient Greek, beta represented the voiced bilabial plosive . In Modern Greek, it represe ...

and

gamma Gamma (; uppercase , lowercase ; ) is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter normally repr ...

radiation. The beta radiation released damages both normal thyroid tissue and any thyroid cancer that behaves like normal thyroid in taking up iodine, so providing the therapeutic effect, whilst most of the gamma radiation escapes the patient's body. Most of the iodine not taken up by thyroid tissue is excreted through the

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

s into the

urine Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...

. After radioiodine treatment the urine will be radioactive or 'hot', and the patients themselves will also emit

gamma radiation A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

. Depending on the amount of radioactivity administered, it can take several days for the radioactivity to reduce to the point where the patient does not pose a radiation hazard to bystanders. Patients are often treated as

inpatient A patient is any recipient of health care services that are performed by healthcare professionals. The patient is most often ill or injured and in need of treatment by a physician, nurse, optometrist, dentist, veterinarian, or other heal ...

s and there are international guidelines, as well as legislation in many countries, which govern the point at which they may return home.

Bone metastasis

Radium-223 Radium-223 (223Ra, Ra-223) is an Isotopes of radium#Radium-223, isotope of radium with an 11.4-day half-life. It was discovered in 1905 by T. Godlewski, a Polish chemist from Kraków, and was historically known as Decay chain#Actinium series, a ...

chloride,

strontium-89 Strontium-89 () is a radioactive isotope of strontium produced by nuclear fission, with a half-life of 50.57 days. It undergoes beta decay, β− decay into yttrium-89. Strontium-89 has an application in medicine. History Strontium-89 was firs ...

chloride and samarium-153 EDTMP are used to treat secondary cancer in the bones.

Radium Radium is a chemical element; it has chemical symbol, symbol Ra and atomic number 88. It is the sixth element in alkaline earth metal, group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, ...

and

strontium Strontium is a chemical element; it has symbol Sr and atomic number 38. An alkaline earth metal, it is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to ...

mimic calcium in the body.

Samarium Samarium is a chemical element; it has symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air. Being a typical member of the lanthanide series, samarium usually has the oxidation state +3. Compounds of s ...

is bound to tetraphosphate EDTMP, phosphates are taken up by

osteoblast Osteoblasts (from the Greek combining forms for " bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cells with a single nucleus that synthesize bone. However, in the process of bone formation, osteoblasts fu ...

ic (bone forming) repairs that occur adjacent to some metastatic lesions.

Bone marrow conditions

Beta Beta (, ; uppercase , lowercase , or cursive ; or ) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Ancient Greek, beta represented the voiced bilabial plosive . In Modern Greek, it represe ...

emitting

phosphorus-32 Phosphorus-32 (32P) is a radioactive isotope of phosphorus. The nucleus of phosphorus-32 contains 15 protons and 17 neutrons, one more neutron than the most common isotope of phosphorus, phosphorus-31. Phosphorus-32 only exists in small quantiti ...

(³²P), as sodium phosphate, is used to treat overactive

bone marrow Bone marrow is a semi-solid biological tissue, tissue found within the Spongy bone, spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It i ...

, in which it is otherwise naturally metabolised.

Joint inflammation

Yttrium-90 colloid

yttrium-90 Yttrium-90 () is a radioactive isotope of yttrium. Yttrium-90 has found a wide range of uses in radiation therapy to treat some forms of cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the ...

(⁹⁰Y)

colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others exte ...

al suspension is used for radiosynovectomy in the

knee In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the hu ...

joint.

Liver tumours

Yttrium-90 spheres

⁹⁰Y in the form of a

resin A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Commo ...

or glass spheres can be used to treat primary and metastatic liver cancers.

Neuroendocrine tumours

Iodine-131 mIBG

¹³¹I-mIBG ( metaiodobenzylguanidine) is used for the treatment of phaeochromocytoma and

neuroblastoma Neuroblastoma (NB) is a type of cancer that forms in certain types of nerve tissue. It most frequently starts from one of the adrenal glands but can also develop in the head, neck, chest, abdomen, or Vertebral column, spine. Symptoms may include ...

Lutetium-177

¹⁷⁷Lu is bound with a

DOTA ''Dota'' is a series of strategy video games. The series began in 2003 with the release of ''Defense of the Ancients'' (''DotA''), a fan-developed multiplayer online battle arena (MOBA) custom map for the video game ''Warcraft III: Reign of Ch ...

chelator to target neuroendocrine tumours.

Experimental antibody based methods

At the

Institute for Transuranium Elements The Institute for Transuranium Elements (ITU) is a nuclear research institute in Karlsruhe, Germany. The ITU is one of the seven institutes of the Joint Research Centre, a Directorate-General of the European Commission. The ITU has about 300 sta ...

(ITU) work is being done on alpha-immunotherapy, this is an experimental method where antibodies bearing

alpha Alpha (uppercase , lowercase ) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter ''aleph'' , whose name comes from the West Semitic word for ' ...

isotopes are used. Bismuth-213 is one of the isotopes which has been used. This is made by the alpha decay of

actinium-225 Actinium-225 (225Ac, Ac-225) is an isotope of actinium. It undergoes alpha decay to francium-221 with a half-life of 10 days, and is an intermediate decay product in the neptunium series (the decay chain starting at neptunium-237, 237Np). Exc ...

. The generation of one short-lived isotope from longer lived isotope is a useful method of providing a portable supply of a short-lived isotope. This is similar to the generation of

technetium-99m Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99 (itself an isotope of technetium), symbolized as 99mTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used Radiophar ...

by a technetium generator. The actinium-225 is made by the irradiation of

radium-226 Radium-226 () is the longest-lived isotope of radium, with a half-life of 1600 years. It is an intermediate product in the decay chain of uranium-238; as such, it can be found naturally in uranium-containing minerals. Occurrence and decay occ ...

with a

cyclotron A cyclotron is a type of particle accelerator invented by Ernest Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Januar ...

References

{{Radiopharmaceuticals Radiation therapy Nuclear medicine