TheraSphere is a

radiotherapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...

treatment for

hepatocellular carcinoma Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults and is currently the most common cause of death in people with cirrhosis. HCC is the third leading cause of cancer-related deaths worldwide. It occurs in t ...

(HCC) that consists of millions of microscopic,

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 consid ...

glass microspheres (20–30

micrometre The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

s in diameter) being infused into the

arteries An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pu ...

that feed liver tumors. These microspheres then embolize, lodging themselves in the liver's capillaries and bathing the

malignancy Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...

in high levels of

yttrium Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a "rare-earth element". Yttrium is almost always found in com ...

- 90 radiation. It is currently approved as a Humanitarian Device, meaning effectiveness has not been proven, for patients as a

neoadjuvant Neoadjuvant therapy is the administration of therapeutic agents before a main treatment. One example is neoadjuvant hormone therapy prior to radical radiotherapy for adenocarcinoma of the prostate. Neoadjuvant therapy aims to reduce the size o ...

to surgery or transplantation by the

U.S. Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

and is being used at a number of clinical centers in the United States.

Description

TheraSphere consists of insoluble glass microspheres where yttrium-90 is an integral constituent of the glass. Each milligram contains between 22,000 and 73,000 microspheres. Yttrium-90 is a pure

beta emitter In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For exam ...

(physical half-life of 64.2 hours or 2.67 days) and decays to stable zirconium-90. The average energy of the beta emissions from yttrium-90 is 0.9367 MeV. The Therasphere package insert contains a Black Box warning concerning 5 Pre-treatment high risk factors associated with serious adverse events resulting in 11/12 deaths. Following

embolization Embolization refers to the passage and lodging of an embolus within the bloodstream. It may be of natural origin (pathological), in which sense it is also called embolism, for example a pulmonary embolism; or it may be artificially induced (t ...

of the yttrium-90 glass microspheres in tumorous liver tissue, the beta radiation emitted provides a therapeutic effect. The microspheres are delivered into the liver tumor through a

catheter In medicine, a catheter (/ˈkæθətər/) is a thin tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. Cath ...

placed into the hepatic artery that supplies blood to the tumor. This is usually performed in a hospital's radiology suite and patients remain conscious throughout the procedure. The microspheres are unable to pass through the

vasculature The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

of the liver due to arteriolar capillary blockade and are trapped in the tumor. There they exert a local radiotherapeutic effect with some damage to surrounding normal liver tissue. Therasphere was issued a Class 2 Device Recall from the FDA in October 2016.

Efficacy

Low-risk patients with unresectable liver cancer appear to gain control over their malignancies for at least 2 years when treated with TheraSphere. They survived a median of 800 days compared with a median of 258 days for high risk patients (P <.0001) in a study of 140 patients (106 male). The patients underwent 238 administrations of the particles. Approximately 34% of patients responded to the treatment according to evaluation by Response Evaluation Criteria in Solid Tumors (RECIST), meaning their overall tumor burden decreased by 50% or more. In a separate study based on follow-up data from 43 treated patients, 20 patients (47%) had an objective tumor response based on percent reduction in tumor size and 34 patients (79%) had a tumor response when percent reduction and/or tumor necrosis were used as a composite measure of tumor response.

References

{{Radiation oncology Radiation therapy procedures

Description

Efficacy

See also

References