Understanding Radiotherapy: More than half of all individuals with cancer will undergo radiotherapy as part of their treatment plan.
What is Radiotherapy and how does it work?
Understanding Radiotherapy: Discovered more than a century ago, radiation has become an integral part of cancer treatment today. More than half of all individuals with cancer will undergo radiotherapy as part of their treatment plan.
Radiotherapy is the use of focused, high-energy photon beams to effectively destroy cancer cells with the least possible harm to the surrounding healthy cells. Radiation oncologists may use radiotherapy as a standalone treatment, or in combination with chemotherapy and surgery.
Unlike healthy cells, cancer cells tend to divide abnormally fast and grow out of control. By using a special equipment that delivers high-doses of radiation, radiotherapy makes small breaks in the DNA inside the cells. When the DNA is damaged, cancer cells stop growing and dividing, and will often die. Healthy cells nearby can also be affected, but unlike cancer cells, they are able to repair themselves.
Radiation has a high affinity for cells that are actively dividing (e.g skin, bone marrow and intestinal lining), but does not work as quickly on cells that are in the resting stage or are not dividing often (e.g nerve, breast, brain, bone tissue). That said, radiation doesn’t always work right away; it may take days to weeks of radiotherapy sessions for cells to start dying.
The goal of Radiotherapy
Radiotherapy is used to treat cancer in several ways:
To treat or shrink a tumor
As a primary, standalone treatment for some cancers that are especially sensitive to radiation. For example, cancers of the prostate and larynx are often treated with radiotherapy alone. Before surgery as a neoadjuvant therapy to reduce the size of the tumor to make it easier to remove. After surgery as an adjuvant therapy to kill any malignant cells which may have remained. Along with chemotherapy because certain chemotherapeutic drugs are radiosensitizers, which means that they make cancer cells more sensitive to radiation.
To prevent certain cancers from metastasizing
Some types of cancers tend to spread to a certain area of the body. For example, individuals with lung cancer may receive a preventative or prophylactic radiotherapy to the head because lung cancers tend to spread to the brain.
To alleviate pain or other symptoms caused by advanced cancer
In cases where cancer has spread too far, radiotherapy may be used to shrink tumors that are impairing a person’s quality of life. Radiotherapy may be used to relieve symptoms such as difficulty breathing and swallowing. This is called palliative radiotherapy; it doesn’t aim to cure the cancer.
Types of Radiation
Radiation used in radiotherapy is called ionizing radiation. This type of radiation forms ions by removing electrons from atoms and molecules, including the DNA molecule. There are two types of ionizing radiation: photon radiation and particle radiation.
By far, high-energy photon beams are the most commonly used form of radiotherapy, the same type of radiation used in x-ray machines. It can come from a radioactive source like cesium, or cobalt. It can also be produced by a machine called a linear accelerator or LINAC. This machine uses electricity to accelerate electrons to almost the speed of light.
Another form of radiation is called non-ionizing radiation. Found in microwaves and radio waves, non-ionizing radiation doesn’t produce as much energy and is not able to form ions.
How is Radiotherapy delivered?
While the utmost goal of radiotherapy is to cure the cancer, preventing damage to healthy tissue is crucial as well. There are many ways to do this, and the technique will depend on the location, size and type of your cancer. You and your treatment team will decide which course of treatment is best.
Generally, radiotherapy can be delivered in three ways:
- External Beam Radiotherapy
- Internal Radiotherapy
- Radiopharmaceuticals
- External Beam Radiotherapy
External Beam Radiotherapy (EBT) uses the LINAC machine, which focuses a beam of radiation on the tumor. EBT can be applied on large areas of the body, and it can also be used to treat more than one area. It is given in an outpatient clinic, and you can go home after each treatment.
Radiotherapy works best in high doses. Unfortunately, healthy cells do not recover well after being exposed to high-dose radiation. So, it is necessary to determine a balance between the maximum tolerable radiation dose of healthy cells and the minimum dose necessary to kill the cancer cells.
Doctors take advantage of the body’s natural healing process by delivering the complete dose in smaller doses or in fractions over several treatment sessions. This method, known as fractionated radiotherapy, allows healthy cells time to recuperate between each session. The principle is that fewer fractions will affect both malignant and healthy cells equally. During fractionated radiotherapy, you will receive treatments daily over 3 to 6 weeks. But some cancers may be treated more than once a day.
Simulation session
For radiotherapy to be most effective, radiation must be precisely aimed at the tumor. In order to pinpoint the target, you will attend a simulation session with a radiation oncologist and a radiation therapist.
During this session, you will be placed on the simulation machine, and the team will determine which position is best for you, and how to help you stay in that position. Next, with the help of advanced imaging techniques, they will mark the radiation field or the treatment port on your body, which is the precise location where the radiation will be aimed at.
What can you expect during radiotherapy?
During the treatment, you may be asked to change into a hospital gown. You will lie on a couch with the LINAC directly positioned over the target area. You will need to stay still as much as possible for each session, which can last up to 30 minutes. The LINAC may make a clicking or whirring sound as it moves in different angles. A special mold may be used to help the treatment part keep still as a slight change in position can compromise the whole procedure.
Internal Radiotherapy
Also called brachytherapy, internal radiotherapy involves implanting radioactive sources into a tumor or inside the affected area. By placing the radiation source close to the tumor, a large dose of radiation can be delivered directly to the malignant cells.
The radiation materials used in brachytherapy include ribbons, thin wires, capsules and seeds that come in small containers. The type of implant you receive depends on the type and location of your cancer, and your general health.
In a high-dose rate brachytherapy (HDR), you will be treated with a powerful radiation source for 10 to 20 minutes at a time, 2 to 5 times a week for at least 2 weeks. The radiation source is not left in place. HDR delivers radiation at a faster rate.
In a low-dose rate brachytherapy (LDR), a radioactive source, usually tiny steel seeds, are left in place for 1 to 7 days. Compared to HDR, LDR emits radiation at a slower rate. You may have to stay in a special room at the hospital during radiotherapy and take extra precautions. Smaller implants may be left permanently. Overtime, the seeds lose their radioactivity.
How is the radioactive source placed in the body?
Before the treatment, you may be put under general anesthesia, or given a local anesthetic to numb the treatment area. Applicators, which can be metal or plastic tubes, are placed within the tumor or the treatment area. When the applicators are in place, the radioactive sources are then loaded. This technique, called afterloading, allows for a more precise, better placement of radioactive sources, and better dose distribution. Afterloading is mainly used for HDR.
Which cancers can be treated with internal radiotherapy?
Internal radiotherapy is often used for the treatment of:
- Breast cancer
- Cervical and ovarian cancers
- Head and neck cancers
- Lung cancer
- Anal cancer
- Prostate cancer
- Gall bladder cancer
- Esophageal cancer
Radiopharmaceuticals
Radiopharmaceuticals are radioactive drugs in liquid form, which are sometimes bound to an organic molecule such as monoclonal antibodies. The organic molecule then delivers the drug to target organs or tissues. Iodine, strontium, samarium and radium are some of the radioactive drugs that are used to treat thyroid, bone and prostate cancers.
How are they given?
Radiopharmaceuticals may be given through the vein or taken by mouth. From there, they travel through the blood and collect in the target area.
Will Radiotherapy make me radioactive?
A common concern among patients with cancer is whether or not radiotherapy will make them radioactive. External radiotherapy uses a machine from where the radiation comes, and your body will not retain the radioactivity.
With brachytherapy, on the other hand, the implant will emit a certain amount of radioactivity. For temporary implants, you will be staying in the hospital and will need to take extra precautions, including visitor restrictions. Radioactivity is usually confined to the treatment area, so your body fluids will not be radioactive, neither will the things you use. Once the implant is removed, there will no longer be a radiation hazard.
Permanent implants lose radioactivity overtime. Again, radiation does not go further than the treatment area, so the chances that you will be a radiation hazard to others is small. Extra precautions are also necessary.
Since radiopharmaceuticals use an unsealed radiation source, some radiation will stay in your body for a few days until it is flushed out. You may need to stay in the hospital for a few days. Your treatment team will advice you on what precautions you should take.
Radiotherapy has been used successfully and effectively by doctors to treat cancer for over 100 years. Over the years, rapid advancements and innovation in medical technology have improved the safety, precision and efficacy of radiotherapy.
One such innovation is gKteso’s Radiotherapy Patient System, a 6-D robotic couch that allows for more precise radiotherapy treatments. Contact us for more information on our technology and providers!
