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Radiotherapy, What Is It and What Is It For?

Radiotherapy is the specialty of nuclear medicine that uses ionizing radiation for the treatment of malignant tumors.

Radiotherapy, what is it and what is it for?

When unencapsulated radioactive sources are used, we speak of metabolic radiotherapy.

This technique consists of injecting or ingesting a relatively large dose of a radioactive substance in liquid form. This substance accumulates in the organ to be treated and emits radiation on the tissues in contact with it. In this way, the emitted radiation destroys the tumor cells.

What Is Radiotherapy?

Radiation therapy is a medical treatment that uses x-rays or other high-powered particles to kill cancer cells. Unlike chemotherapy, radiation therapy cannot be used to treat all types of cancer.

This type of radiation treatment can be given in several ways: 

  • External radiation therapy: The radiation source is outside the body.

  • Internal radiation therapy: The source of radiation is inside the body.

What Is Radiotherapy Used For?

Radiation therapy is a medical treatment that is used to destroy cancer cells. It is often used along with other treatments, such as chemotherapy and surgery.

Radiation therapy can be used to treat patients with cancers of the lung, breast, prostate, head and neck, uterus, ovaries, testicles, hyperthyroidism, thyroid cancer, bone metastases from prostate tumors, and brain tumors. Radiation therapy can also be used to relieve pain caused by cancer.

In the case of thyroid cancer, iodine-131 is used, which is a gamma emitter. In this case, the patient is admitted to special units that have radioprotection units and specialized medical care.

Once the patient has been discharged, a dosimetric control is carried out periodically to monitor and verify that, due to its low doses of gamma radiation, the patient can live with his family and the rest of the population.

Examples of Radiation Therapy Treatments

Radiotherapy applications include teletherapy and brachytherapy


Teletherapy is a radiotherapy nuclear medicine technique in which the radioactive source is not in direct contact with the tumor being treated.

Among the gamma emitting sources used, the encapsulated source of cobalt-60 stands out, contained in the so-called cobalt bomb, which prevents radiation from escaping except through a hole that provides directed radiation.

Teletherapy produces high-energy radiation (1.2 MeV) capable of irradiating large, deeply located tumors. Teletherapy can also be administered with sources emitting electronic and neutron beams.

Objective of Treatment by Teletherapy

There are different nuclear medicine treatments through teletherapy focused on achieving different objectives:

  • Radical or curative treatment: In radical therapy, the purpose of treatment is to destroy the tumor and cure the patient.

  • Palliative medical treatment: The purpose of palliative care is primarily to reduce disease-induced tumor signs (pain relief, tumor-related bleeding), even though we know the disease is no longer curable. The essential purpose of palliative care is primarily to allow patients to live as long as possible with a good quality of life, even though the cancer cannot be destroyed.

  • Preoperative Treatment: The purpose of preoperative irradiation is to irradiate with the goal of shrinking the tumor before the actual surgery.


Brachytherapy is a type of radiotherapy treatment in which the tumor receives radiation by direct contact with the radioactive source. This technique is also known by the name of Curietherapy.

There are three brachytherapy treatment options:

  • Superficial brachytherapy: plates of radioactive material are placed over the tumor area.

  • Intracavitary brachytherapy: the radioactive source is temporarily introduced into the patient's natural cavities. For this technique, encapsulated sources of cesium-137 are usually used.

  • Interstitial brachytherapy: The radiotherapy technician places the radioactive sources in certain tissues of the patient. 

One of the problems with this type of radiotherapy is the possible unnecessary exposure of the patient and healthcare personnel to radiation from the sources. To avoid this inconvenience, the source must be placed in the correct position in the patient receiving radiotherapy. To do this, health personnel use remote control controls to prepare, transport and manipulate radioactive sources.

Radiation Therapy Side Effects

Radiotherapy can cause side effects in the patient as they can kill healthy cells. Some of these effects are acute and transient, while others are delayed and persistent. The acute ones usually appear during treatment or immediately after, while the late ones may not manifest until months or years after treatment.

The side effects of radiation therapy depend on various factors, such as the dose administered, the area of ​​the body irradiated, and the individual sensitivity of the patient.

Most side effects are mild and reversible, and go away after treatment is finished. However, some side effects can be serious and/or irreversible.

Radioprotectants are currently being studied to protect normal cells in healthy tissues that may be affected by treatment. 

It is important to talk to your doctor about possible side effects before starting treatment.


Published: October 2, 2015
Last review: March 16, 2023