Radiotherapy is one of the most widely used techniques to address cancer, but it is divided into different methodologies, depending on the needs of the patient. Here we tell you.
On a biological level, cancer seems almost like 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 uncontrollably, they form a tumor and, in the worst cases, can enter the bloodstream or lymphatic and colonize a new tissue, leading to the dreaded metastasis.
Something as simple as what we have just described is, today, one of the biggest health problems worldwide. More than 32 million people worldwide live with cancer at any given time and, unfortunately, more than 8 million patients lose their fight against their tumors annually. Almost one in 6 deaths on the planet are due to this malignancy.
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 testicle) have a survival rate of 99%. The detection of 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 no small thing. Based on this premise difficult to treat but hopeful, we show you the 8 types of radiotherapy and their characteristics.
- We recommend you read: “The 7 cancer treatments (and their characteristics)”
What is radiation therapy and how is it classified?
Radiotherapy (RT) is a clinical modality that uses ionizing radiation to treat different types of malignancies (and some benign diseases, occasionally). This technique seeks to destroy cancer cells with as little damage as possible to surrounding tissues, something that seems difficult with a chemotherapeutic treatment.
65% of cancer patients worldwide require radiotherapy as a single treatment or combined with surgery and/or chemotherapy but, unfortunately, not all regions of the planet have the necessary infrastructure to perform a RT-based approach. Therefore, we are not surprised to learn that 70% of cancer deaths annually occur in lower-middle-income countries.
El mecanismo exacto por el cual las células cancerígenas mueren por los rayos ionizantes sigue bajo investigación, pero se cree que uno de los factores más importantes es la rotura de las 2 hélices de ADN que forman el genoma de la estirpe maligna. Esta rotura compromete severamente la integridad reproductiva de la célula y, por ende, muere sin poder multiplicarse.
The success of radiation therapy depends on the tumor’s sensitivity to radiation and tolerance of surrounding tissues (NTTs). On the other hand, the “lethal tumor dose” (TLD) defines the radiation dose necessary for the tumor to undergo 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 radiotherapy, we can introduce you to the different types used to treat cancer patients. Don’t miss it.
1. Three-dimensional conformal radiation therapy (3DCRT)
This type of radiation therapy uses computed tomography (CT) to tailor treatment to the exact shape of the tumor. The goal of 3DCRT is todeliver ionizing radiation as precisely as possible tothe tumor, 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 as little as possible to the tissues that are close to the tumor. As you can imagine, this variant is used in patients with neoplasms near organs very sensitive to radiation.
3. Volumetric modulated arc therapy (VMat)
The VMat was introduced for the treatment of some types of cancer for the first time 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 capable of rotating continuously around the patient’s body. With this modality, treatment time is reduced, accuracy is improved and the radiation beam reaching the tumor is maximized.
4. Image-guided radiation therapy (IGRT)
In this case, images of the patient’s body are taken with X-rays 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 occur in nearby tissues.
5. Stereotactic radiation therapy (SRS)
In this modality, a three-dimensional coordinate system independent of the patient is used for the location of a lesion. In addition, the radiation beams produced are shaped, precise and convergent, so that the tumor can be attacked in a localized way with minimal damage to the surrounding structures.
If this procedure is performed in a single session, it is known as radiosurgery, while in prolonged periods it is called stereotactic radiation therapy (SRS). In addition, it should be noted thatit 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 relies 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)
On this occasion, X-rays are used with a low degree of penetration into the patient’s tissues. As the waves do not travel much, they are perfect for the treatment of skin cancers, since the organs and internal structures of the patient are minimally involved during the procedure.
8. Intraoperative radiation therapy (IORT)
As the 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. Therefore, it is very useful in patients who have already suffered relapses after previous treatments or who, failing that, have an advanced tumor with a wide degree of dissemination.
Summary and final considerations
To close this topic, we again recover the therapeutic index (TI) value, that is, the tolerance of adjacent 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 addressed with the types of radiotherapy mentioned here.
Some examples of cancers with very high IT are lymphomas, seminomas, leukemias and many other examples. This means that the tissue involved withstands radiation relatively well, while the tumor is very sensitive to the methodology used. On the other side of the coin, with very low IT we have osteosarcomas, melanomas and sarcomas in soft tissues, among others.
Therefore, we must emphasize that these types of treatments are extremely effective in some cases, but report a poor prognosis in others. In addition, sometimes radiotherapy must be combined with surgery and drug treatments, because its action alone is not enough to eradicate the entire threat of cancer. Each patient is different and, therefore, each approach must be carried out individually and uniquely.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.