The 14 types of radiotherapy (characteristics and objectives)

Cancer has been, is and will continue to be the most feared disease in the world. And not only because of the fact that there is currently no cure, but because of the 18 million cases diagnosed annually around the world and because of the tremendous psychological impact it has on both the patient and their loved ones.

Even so, it is very important to be clear that, today, "cancer" is not synonymous with "death." Perhaps long ago it was; but in the present, no. And is that Although cancer remains an incurable disease, this does not mean that it is not treatable.

The vast majority of cancers can not only be treated, but also have survival rates that can reach rates of more than 90%. And this is thanks to the incredible advances in oncology, which has allowed us to have different forms of treatment, choosing one or the other depending on many factors, both of the malignant tumor itself and of the patient.

In today's article we bring all the important information (and from the hand of the most prestigious scientific publications) about one of the most common forms of cancer treatment: radiation therapy. We will see what it consists of and what its main types are, also analyzing when one or the other is suitable.


    What is radiotherapy?

    Radiation therapy, also known as radiation therapy, is an oncological treatment technique that is based on the use of ionizing radiation with the aim of treating different cancers. That is, it is a therapy to destroy cancer cells associated with malignant tumors by applying high doses of radiation.

    That is, while low-dose radiation is used for image recognition techniques (the famous X-rays), at high doses it allows to shrink tumors and kill cancer cells, thus being a strong candidate for cancer treatment.

    In this sense, radiation therapy involves the use of high-powered x-rays, gamma rays, or other particles (electrons, protons, neutrons and heavy ions) to treat cancer. These high-energy ionizing radiations damage cellular DNA, thus destroying cancer cells or, at the very least, slowing the growth of the malignant tumor, as they die or stop dividing, respectively.

    When these cancer cells die, the body discards them. Even so, as is evident, this radiation is not only harmful to tumor cells, but also to healthy cells in nearby tissues. Therefore, despite the fact that the radiation strikes only the tumor, it is impossible to avoid side effects that depend on the area of ​​the body where the radiation strikes. Hair loss, tiredness, skin changes, nausea and vomiting, blurred vision, urinary disorders, and headaches are the most common.

    Similarly, it is important to note that radiation therapy does not kill cancer cells right away. For their DNA to be damaged enough that they die or stop dividing, weeks of treatment may be required..

    Be that as it may, in some patients it may be that this radiation therapy is the only treatment they need, but the most common is that such radiation therapy is combined with other forms of cancer treatment such as surgery, chemotherapy and immunotherapy.

    In summary, radiotherapy is a form of local treatment (acts only on the tumor) based on the use of ionizing radiation (X-rays, gamma rays or high-energy particles) capable of damaging the DNA of cancer cells and thus treating the cancer in question.

    How is radiation therapy classified?

    After you understand what radiation therapy is, it is time to see how it is classified. We will analyze the different types of radiotherapy (and which cancers are treated with each one) based on different parameters: according to the distance from the radiation source, according to the purpose and according to the time sequence.

    The type of radiotherapy required will depend on many factors: location, degree of spread, type of cancer, size of the malignant tumor, age of the patient, suffering from other diseases, application of other anti-cancer therapies in the past, general state of health, proximity to tissues especially sensitive to radiation, clinical history, etc.

    1. According to the distance from the radiation source

    This is the most relevant classificatory parameter at the oncological level. Depending on the distance to the radiation source, we can describe two main types: external beam radiation therapy and internal radiation therapy. Let's see its peculiarities.

    1.1. External beam radiation therapy

    External beam radiation therapy is the most common form of radiation therapy. Ionizing radiation comes from a machine large and noisy known as a linear accelerator or LINAC, which focuses this radiation on the cancer or malignant tumor. This machine adjusts the shape and size of the radiation beam to direct it exactly on the tumor, avoiding that the incidence on healthy tissue is minimal. It is used to treat many different types of cancers.

    External beam radiotherapy presents, in turn, different types, each having its own particularities:

    • Three-dimensional conformal radiation therapy: It is a type of external beam radiotherapy in which highly detailed three-dimensional images of the malignant tumor are generated, which allows the cancer to be treated with greater precision and higher doses of radiation can be used by not compromising adjacent healthy tissues as much .

    • Intensity modulated radiation therapy: This is a three-dimensional variation where a modulation component is added, in the sense that it allows the intensity of each beam to be varied. In other words, we can have different radiation beams of different intensity to affect the malignant tumor even more precisely.

    • Stereotactic radiation therapy: This is a form of radiation therapy that usually consists of a single (or few) sessions in which the patient receives a high dose of radiation. It is applied in small tumors, but being of high intensity and due to the danger of it affecting nearby tissues, the person must remain totally immobile.

    • Image-guided radiation therapy: This form of radiation therapy is helpful in monitoring the progression of the malignant tumor during treatment. It allows to obtain images throughout the therapy to compare the results with the initial situation.

    • Proton beam therapy: This form of radiation therapy is not really radiation therapy, since ionizing radiation is not used. Instead of using X-rays or gamma rays, the treatment involves striking protons. At high energies, it is possible to form bundles of these subatomic particles that kill cancer cells. It is very effective and the damage to healthy tissues is minimal, since the precision of this beam is unmatched. Unfortunately, being a relatively new and very expensive therapy, it is not available in all hospitals. Hopefully in the future its use will spread more.

    As we can see, there are many forms of external beam radiation therapy, as it is very useful in the treatment of localized cancers and attempts to minimize damage to healthy tissues near the tumor. Even so, there are times when you have to resort to internal radiation therapy.

    1.2. Internal radiation therapy

    Internal radiation therapy is a form of radiation therapy in which the source of radiation is inserted into the body.. That is, the radiation does not come from an external machine, but from radioactive materials that enter the malignant tumor or the healthy tissue that surrounds it.

    Depending on whether the radiation source is solid or liquid, we have two main types of internal radiation:

    • Brachytherapy: This is a form of internal radiation therapy in which the radiation source is solid. It is still a form of local treatment, as the steel seeds, strips or capsules of radioactive material are placed only in or near the tumor, so there is only a noticeable incidence of radiation in a specific region of the body. These implants release radiation for a time (the person must isolate themselves to protect others) until they lose their radioactivity. Brachytherapy is often used to treat cancers of the head and neck, breast, prostate, eye, and cervix.

    • Systemic therapy: This is a form of internal radiation therapy in the one that the radiation source is liquid. As we can deduce from its name, it is not a form of local treatment, but being liquid, the radiation circulates through the blood and reaches all the tissues of the body. Administered orally or intravenously, this radiation in liquid form consists of radioactive iodine and is generally used to treat certain types of thyroid cancers. There is more damage at the systemic level (because it does not affect only the tumor) and the person's body fluids will be radioactive for a while, but there are times when there is no other option but to resort to this liquid therapy.

    There is another form of systemic radiation therapy known as targeted radionuclide therapy or molecular radiation therapy, which involves the use of a radionuclide (a radioactive chemical) that contains antibodies that allow it to bind to antigens on cancer cells. However, it is currently only used to treat advanced prostate cancer or gastroenteropancreatic neuroendocrine tumors. Thus, the two most important are still brachytherapy and liquid radiation therapy.

    2. According to the purpose

    As we have said, the most important classification is the one we have seen before. However, it is also important to know how radiation therapy is classified according to its purpose. And it is that cancer treatment by radiation can have two objectives: cure or alleviate. And, in this context, we have curative radiation therapy and palliative radiation therapy.

    2.1. Curative radiation therapy

    As its name suggests, curative radiation therapy is one that is intended to treat cancer so that the patient overcomes the disease. Higher doses of radiation close to the body's tolerance limit are used to kill cancer cells and kill the malignant tumor responsible for the cancer. In this case, the benefits of the potential cure outweigh the dangers of the treatment side effects.

    2.2. Palliative radiation therapy

    As its name suggests, palliative radiation therapy is one that has the purpose of alleviating the symptoms of cancer. Lower doses of radiation far from the body's tolerance limit are used not to kill the malignant tumor, but to calm or alleviate the symptoms of cancer. Palliative treatment is shorter and less intense since what is sought is not a cure, but the fewest possible side effects.

    Palliative radiotherapy seeks to alleviate the most distressing symptoms of cancer (such as certain hemorrhages), reduce the appearance of these symptoms, improve the patient's quality of life and ensure that they maintain their autonomy for as long as possible while other treatment therapies are performed. cancer that they are destined to cure. And, obviously, in the event that cancer cannot be cured by chemotherapy or immunotherapy, ensure that death arrives in the best possible conditions.

    3. According to the temporal sequence

    Finally, radiotherapy can also be classified according to its temporal sequence, that is, depending on the moment and the conditions in which said radiation therapy is performed. In this sense, radiation therapy can be exclusive, adjuvant, or synchronous.

    3.1. Exclusive radiation therapy

    Exclusive radiotherapy refers to that clinical situation in which radiotherapy, in any of its previously analyzed forms, it is the only cancer treatment that the patient will receive. If cancer is diagnosed early, only radiation therapy may be necessary. Even so, this is not very common, since in the early stages surgery is tried, which has fewer side effects. For this reason, exclusive radiotherapy is typical of certain cancers that, in their early stages, cannot be treated with surgery, something common in prostate cancer, for example.

    3.2. Adjuvant radiation therapy

    Adjuvant radiation therapy is already more common. This is the clinical situation in which radiotherapy is a form of secondary treatment that seeks to enhance the effectiveness of a primary treatment. The most common situation is that radiation therapy is the adjunct (add-on treatment) to surgery, which tends to be the primary treatment for many early-stage cancers. The surgery is done first, followed by radiation therapy.

    3.3. Synchronous radiation therapy

    Synchronous radiation therapy refers to the clinical situation in which radiation therapy is applied in conjunction with another form of cancer treatment. The most common is that radiotherapy is synchronous with chemotherapy, which means that they are applied at the same time and there is not a main and a complementary one, but both therapies mutually enhance each other. When the cancer is in more advanced stages, synchronous radiation therapy, also known as concurrent or concomitant, is more common.

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