The 8 Types of Radiotherapy And their Characteristics
Radiation therapy is one of the most widely used techniques to address cancer, but it is divided into various methodologies, depending on the needs of the patient. Here we tell you.
On a biological level, cancer seems almost an anecdotal event. A cell line undergoes a sporadic mutation and, due to changes in its genome, does not respond to normal division and senescence processes. As this group of cells grows out of control, they form a tumor and, in the worst cases, can enter the blood or lymphatic stream and colonize new tissue, leading to the dreaded metastasis.
Something as simple as what we have just described is, today, one of the biggest health problems in the world . More than 32 million people around the world are living with cancer at any given time and, sadly, more than 8 million patients lose the fight against their tumors annually. Almost one in every 6 deaths on the planet is due to this malignant neoplasm.
The data continues to fall like vases of cold water, but we do not want you to stay with the negative part of this group of pathologies. 30% of cancers arise from controllable events (smoking, drinking, sedentary lifestyle, addictions, and other habits) and some tumors (such as testicular) have a 99% survival rate. Detecting a tumor is not the end of the road, but the beginning of a battle that is more than possible to win.
The cancer patient has family, science and health on his side, so it is time to stand up to that group of rebellious cells and give everything to live, which is not little. Based on this difficult to treat but hopeful premise, we show you the 8 types of radiotherapy and their characteristics .
What is radiation therapy and how is it classified?
Radiation therapy (RT) is a clinical modality that uses the use of ionizing radiation to treat different types of malignant neoplasms (and some benign diseases, occasionally). This technique seeks to destroy cancer cells with the least possible damage to the surrounding tissues, something that seems difficult with a chemotherapy treatment.
65% of cancer patients in the world require radiotherapy as a single treatment or combined with plastic surgery and / or chemotherapy, but unfortunately, not all regions of the planet have the necessary infrastructure to carry out an RT-based approach. Therefore, we are not surprised to learn that 70% of cancer deaths annually occur in lower-middle-income countries.
The exact mechanism by which cancer cells are killed by ionizing rays remains under investigation, but it is believed that one of the most important factors is the breakage of the 2 DNA helices that make up the genome of the malignant lineage . This rupture severely compromises the reproductive integrity of the cell and, therefore, it dies without being able to multiply.
The success of radiation therapy depends on the sensitivity of the tumor to radiation and the tolerance of the surrounding tissues (NTT). On the other hand, the “lethal tumor dose” (TLD) defines the radiation dose necessary for the tumor to undergo a complete and permanent regression. Thus, radiotherapy is conceived if the therapeutic index (TI) is positive, that is, if the tissue is able to “withstand” the radiation necessary to kill the cancer.
- Treatment Therapeutic Index (TI) : Tissue Tolerance (NTT) / Lethal Tumor Dose (TLD)
Now that you know the physiological mechanism of radiation therapy, we can introduce you to the different types that are used to treat cancer patients. Do not miss it.
1. Three-dimensional conformal radiation therapy (3DCRT)
This type of radiation therapy uses computed tomography (CT) to tailor the treatment to the exact shape of the tumor. The goal of 3DCRT is to deliver ionizing radiation as precisely as possible to the tumor, thus allowing the rest of the surrounding tissues to suffer minimal damage.
2. Intensity Modulated Radiation Therapy (IMRT)
In this type of RT, linear accelerators are used to safely deliver specific doses of radiation to a tumor. The intensity of the x-ray beam is controlled by a computer and produced in small volumes, in order to damage the tissues that are close to the tumor as little as possible. As you can imagine, this variant is used in patients with neoplasms near organs that are highly sensitive to radiation.
3. Modulated volumetric arc therapy (VMat)
VMat was first introduced for the treatment of some types of cancer in 2007, so this is a variant that is in its infancy. In this case, state- of-the-art linear accelerators are used , which are able to rotate continuously around the patient’s body. With this modality, treatment time is reduced, precision is improved, and the radiation beam reaching the tumor is maximized.
4. Image Guided Radiation Therapy (IGRT)
In this case, X-ray images of the patient’s body are taken before, during and after the session, in order to increase the precision and accuracy of the treatment. Again, this technique tries to minimize the damage that can be produced in nearby tissues.
5. Stereotactic radiotherapy (SRS)
In this modality, a patient-independent three-dimensional coordinate system is used to locate a lesion. In addition, the radiation beams produced are shaped, precise and convergent, so the tumor can be targeted locally with minimal damage to neighboring structures.
If this procedure is performed in a single session, it is known as radiosurgery, while in prolonged periods it is called stereotaxic radiation therapy (SRS). In addition, it should be noted that it is used to direct radiation beams to special areas of the brain , without the need for anesthesia, surgery per se or incisions.
6. Brachytherapy
This type of radiation therapy is based on placing a radioactive source directly into or next to the patient’s tumor. The radioactive elements travel in protective capsules, which go through a series of applications or can even be placed directly through a surgical procedure. It is useful in prostate or gynecological cancers, for example.
7. Superficial radiation therapy (SXRT)
This time, X-rays with a low degree of penetration into the patient’s tissues are used . As the waves do not travel too much, they are perfect for the treatment of skin cancers, since the internal organs and structures of the patient are minimally compromised during the procedure.
8. Radioterapia intraoperatoria (IORT)
As its name suggests, intraoperative radiation therapy occurs in an operating room. On this occasion, the moment of surgical removal of the tumor is used to apply a special dose of radiation to the affected area, to prevent a recurrence over time. For this reason, it is very useful in patients who have already suffered relapses after previous treatments or who, failing that, have an advanced-stage tumor with a wide degree of dissemination.
Summary and final considerations
To close this issue, we once again recover the therapeutic index value (TI), that is, the tolerance of the neighboring tissues (NTT) divided by the lethal tumor dose (TLD). We do not do it for pleasure, since this value perfectly exemplifies that, unfortunately, not all tumors can be treated with the types of radiotherapy mentioned here.
Thank you,
Glenda, Charlie and David Cates
