Radyoterapi ve Beslenme
Radiotherapy is primarily used in the treatment and ongoing management of cancer patients and their malignancies.
Radiotherapy is the use of ionising radiation in the treatment of cancer and is the ability of radiation to interact with the atoms and molecules of the tumour cells to produce specific harmful biological effects.
Ionisation affects either the molecules of the cells or the environment in which the cell lives; that is, there is sufficient energy from the radiation to cause changes within the cell.
The international unit for radiation dose is Gray (Gy).
Each type of radiation has its own unique characteristics. Your Radiation Oncologist will select different types of radiation dependent upon the area of the body they are treating.
For example, skin cancers are usually treated with electrons as they tend to deposit their energy on the surface.
X-ray tends to deposit most of its energy in deeper tissue and is therefore, for example, very useful in the treatment of prostate and cervical cancers. The benefit of x-ray therapy is that a high dose can be delivered directly to the cancer with minimal direct dosing to the skin.
How is radiation produced?
Most Radiation Oncology Departments have machines called linear accelerators which are capable of producing x-ray or electron radiation on demand.Once the machine is switched off, the radiation stops.
That is why cancer patients are not radioactive when they leave the treatment room and there is no risk to the people who come in contact with them.
In contrast are radioactive isotopes. These come as an oral or intravenous preparation.
For example, iodine – 131 which is used to treat overactive thyroids or thyroid cancer.
The radioactive isotopes can also be implanted directly into the tumour or into body cavities. This form of treatment is called brachytherapy. For example the implantable radioactive isotope wires Iridium-192 can be implanted into cancers of the tongue.Caesium-137 is another example of an implantable radioactive isotope used in the treatment of uterine or vaginal cancers in conjunction with other therapies, i.e. chemotherapy.
If radioactive isotopes are left inside the person they will of course continue to emit radiation.
Therefore there are strict guidelines that need to be adhered to such as the type of hospital room used for their stay, contact time with family and nursing precautions.
How does radiotherapy work?
The majority of the cells in our body contain DNA (Deoxyribonucleic acid). DNA is also the principle target of ionising radiation.
Radiation either directly disrupts the DNA activity or produces fast moving charged particles called radicals, which then disrupt the DNA activity.
Radiation tends to damage cancer cells more than normal cells because cancer cells are rapidly synthesising DNA, and hence have more targets for radiation. No doubt, some normal cells will also be destroyed and as a result side effects can occur.
Why does it take time for radiotherapy to work?
Radiation obviously has an immediate effect on the DNA and other targets. However, this does not immediately cause the irradiated cells to die. Even though the DNA is damaged at the standard dose of radiation used in cancer treatment, the rest of the cell structures remain viable and continue to work.
It is only when the time comes for the cell to divide that it finds the very blueprint for itself (ie. the DNA) faulty and thus it dies. It may be up to a month before the cancer cells attempt to reproduce and then die. (Please note however that in certain tissues, radiation does induce a rapid death by other mechanisms. i.e.
The radiation damages cells that are actively dividing. We often discuss the phases of cell division as the ‘The Cell Cycle’.
What does radiotherapy involve?
Radiation is directed to the area in which the cancer is located through either external beam or implants. Radiotherapy works in a similar way to chemotherapy, in killing the cells that are actively dividing through the damage of DNA.
Radiotherapy doesn’t have the systemic side effects seen with chemotherapy, but this is not to say that radiotherapy does not have side effects. The side effects of radiotherapy are localised to the site of the tumour.
For example, radiotherapy to a tumour in the neck may cause a sore throat but will not cause diarrhoea.
Radiotherapy is delivered either by external beam radiation, which is similar to the way an x-ray is taken (however in much stronger doses) by the insertion of radioactive implants (brachytherapy) or via isotope therapy.
Side effects of radiotherapy
As mentioned earlier, the side effects of radiotherapy are specific to the sites that are being treated. Potential for side effects increases with increasing duration of treatment, expected side effects usually appear 14 days after commencement of treatment and depend on dose, site and volume of treatment.
Some of these include:
- Acute nausea and vomiting;
- Inflammatory responses in irradiated tissues (e.g. mucositis, cystitis, proctitis);
Delayed side effects:
- Radiation fibrosis and specific organ damage: Any organ can be damaged with a sufficient dose. Some only need a low dose (e.g. lens);
- Sterility: gonads or pituitary;
- Secondary cancers.
Radiotherapy is not specific for cancer cells, and so can be dangerous to the normal cells of the patient. Procedures must always be followed that ensure the patient is only being exposed to the prescribed dose of radiation, and that this is being directed at the correct site.
Radiotherapy generally has less systemic side effects than chemotherapy because of this direction. For this reason, it is possible for a patient to lead a relatively normal life (including getting pregnant providing the cancer is not in the pelvic region) whilst receiving radiotherapy.
|For information on breast cancer, types of breast cancer and its investigations and treatments, as well as some useful videos, see Breast Cancer.|
|For information on prostate cancer, including diagnoses, types of treatments, and some useful tools, videos and animations, see Prostate Cancer.|
What is radiotherapy?
The beams of radiation in radiotherapy are more powerful than ordinary X-rays. They aim to destroy the cancer cells with as little damage as possible to normal cells.
- Radiotherapy can be given on its own or with surgery, chemotherapy, hormone therapy or monoclonal antibody therapy. It can be given before surgery to shrink the tumour or after surgery to treat any residual disease.
- Radiotherapy can be given from outside the body (externally) or from inside (internally).
- Radiotherapy in general is safe. Depending on the type of radiotherapy, you may need to take special precautions after treatment.
- Radiotherapy may cause side effects that can last for a short or a longer period.
When you may need radiotherapy
Your doctor may prescribe radiotherapy to destroy the tumour: this is called curative radiotherapy. You may also have radiotherapy to relieve symptoms ( pain): this is called palliative radiotherapy.
Radiotherapy can be given before or after surgery. When it is given before surgery, it is called neo-adjuvant therapy. When given after, it can prevent any cancer cells left in your body from growing, and is called adjuvant therapy.
You can get radiotherapy in special cancer treatment centres. The radiotherapy unit may not be located in the hospital where you receive your cancer diagnosis. As a result, you may have to travel to a special radiotherapy centre for treatment.
We may be able to help you with the costs of your travel expenses.
Types of radiotherapy
There are different ways to give radiotherapy. It can be given from outside the body (externally) or from inside (internally). Sometimes both are used to treat cancer, for example, in the breast or prostate gland.
External beam radiotherapy
Giving radiotherapy externally is called external beam radiotherapy and a course can last 4–8 weeks. The rays come from a machine called a linear accelerator or other machines called cobalt. The different types of external beam radiotherapy include:
- Conformal radiotherapy (3D)
- Intensity-modulated radiotherapy (IMRT)
- Stereotactic radiotherapy
This is also called 3D conformal radiotherapy. Here CT or MRI scans are used to make a three-dimensional (3-D) computer image of your tumour and nearby tissues.
The radiotherapist puts metal blocks in the path of the radiation beam; the blocks change the shape of the beam so that it conforms more closely to the shape of the tumour.
This allows a higher dose of radiation to be given to the cancer and a much smaller dose to normal tissue. This helps to reduce the risk of long-term side effects.
Intensity-modulated radiotherapy (IMRT)
With IMRT, your specialist can change the dose and match the shape of the rays to the shape of your tumour. The entire tumour gets the same dose of radiation, while healthy tissues close to the tumour receive a lower dose. This helps to prevent long-term side effects.
If you would to know more about different types of radiotherapy, please see our section on advanced radiotherapy.
External radiotherapy treatment visits
Your first visit to the radiotherapy unit will be for planning purposes only. You will be asked to lie on a hard table and stay still for a few minutes while a machine called a simulator takes X-rays and scans of the area to be treated. This will help to plan the correct position for your radiotherapy.
Before treatment can begin, your skin will be marked to show where the treatment is to be aimed. This is done with ink or a permanent tattoo. The rays are then aimed at the same area each day. Do not rub off any marks made with ink until your treatments are over.
This planning visit can take up to 45 minutes.
You will visit the radiotherapy unit each weekday with a rest at weekends. This could last for up to 8 weeks.
The radiotherapy machine moves around your body but does not touch you and makes very little noise. It is having an X-ray and you will not feel anything during the treatment.
You will be on your own in the treatment room but the radiation therapists will be able to see and hear you.
The treatment visits are much shorter than the planning visit. The treatment only lasts for about five minutes but your appointment will take about 15-20 minutes. This is because the radiation therapists will need time to put you in the right place on the treatment table.
Internal radiotherapy (brachytherapy)
Brachytherapy or ‘close dose’ therapy is a delivery system that provides high dose radiation to a small volume of tissue.
Internal radiotherapy is given in 2 main ways:
Putting radioactive seeds or rods inside your tumour (used in the treatment of prostate, cervical and endometrial cancer)
As radioisotopes to treat thyroid cancer. This will take the form of a drink or capsule or as an injection into a vein.
There are 2 types of brachytherapy, depending on the dosage:
- Low-dose-rate (LDR) brachytherapy
- High-dose-rate (HDR) brachytherapy
This involves putting radioactive seeds directly into your tumour and leaving them there permanently. In Ireland, LDR brachytherapy tends to be used for treating men with prostate cancer. Inserting the seeds requires a straightforward surgical procedure.
Before the procedure:
Your doctor may arrange some tests to check that your heart, lungs and kidneys are working well. Tell your doctor if you are taking any tablets to thin your blood, such as aspirin or Warfarin.
During the procedure:
You will not feel anything, as you will be put to sleep under general anaesthetic. The seeds will be put in using long needles and X-rays to guide the doctor. The number of seeds used depends on your type of tumour. The seeds are left in place and slowly release radiation over several months. The treatment is usually completed in a single visit.
After the procedure:
Once the procedure is finished, you will be taken to a room to recover until you are fully awake. You will usually be discharged from hospital the same day once you have had something to eat and drink.
Arrange for someone to bring you home. It is best not to drive for at least 12 hours afterwards. You will need to take antibiotics for a few days afterwards to prevent any infection. Before you leave, you will be given the contact details for the hospital and a follow-up appointment as well.
High dose rate (HDR) brachytherapy
This is used mainly to treat cancers in the head and neck area, the cervix, womb, prostate or the skin. High dose rate (HDR) brachytherapy involves a temporary implant of radioactive material (the source).
Tubes called applicators are put into your tumour under general anaesthetic so that the radioactive source can reach the tumour. The radioactive source stays close to or inside the tumour between 5 and 15 minutes, sometimes you may need a few treatments a week apart. In some hospitals the applicators are left in place between treatments. Once the treatment is over the tubes are removed.
Radioisotopes for thyroid cancer
For cancer of the thyroid, the radiation source may be unsealed or open. It involves using a liquid source of radiation called a radionuclide (radioisotope). It can be given as an injection into a vein but is more usually taken by mouth as a capsule. Unsealed sources are radioactive until your body gets rid of them.
Before treatment you will be brought to a special room with an en-suite. Here you will be asked to take a capsule of radioactive iodine.
You will have to stay in this room for a number of days as your urine and stools will be radioactive. Usually after three days you will be allowed home.
Your doctor, nurse or physicist will advise you on any precautions that need to be taken about this type of treatment.
How long do courses of radiotherapy last
How much treatment you receive will depend on the size, location and type of cancer. Your treatment will be planned to suit your situation. Even patients with the same type of cancer may have different radiotherapy treatments. Your doctor will discuss this with you.
With external radiotherapy, treatment can last from 4 to 8 weeks. With LDR brachytherapy, you will have one visit to put the seeds in and they stay in permanently. With HDR brachytherapy you may need only 1 treatment.
Is radiotherapy safe?
In general, radiotherapy is safe. Depending on the type of radiotherapy you receive, you may have to take some special precautions.
It is safe to be with other people, including children, throughout your treatment.
Low dose rate (LDR) brachytherapy
Although the seeds are radioactive, you are not. It is fine for you to be among people. But you do need to be careful around women who are pregnant and young children.
It is fine for you to give them a quick hug or to be in the same room as them.
But it is best not to allow children to sit on your lap or sit next to a pregnant woman for long periods of time for two months after treatment.
Special care will be taken after treatment with a liquid radioisotope.
- You will most ly be in a side room, away from the main ward.
- The doctors and staff on the ward will only stay in your room for short periods at a time.
- Children and pregnant women will not be allowed to visit.
- The level of radiation in your room will be monitored. The nurses may wear a small radiation counter.
- Visitors may only be allowed to stay in the room or sit at the end of the bed for a very short time, if at all.
- You will only be in the side room for a short time. You will be able to watch TV or listen to the radio and can bring books and magazines to read.
If you would to know more about different types of radiotherapy, please see our section on advanced radiotherapy.
Side-effects of radiotherapy
For more information on the side-effects of radiotherapy please see our page on the side-effects of cancer treatments.
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Radiotherapy of the brain (fractionated)
Radiotherapy uses high-energy rays to destroy tumors and other diseases. Radiation works by damaging the DNA inside cells and makes them unable to divide and grow. Radiotherapy uses low dose beams to treat the tumor and a margin of normal cells surrounding the target area to prevent regrowth.
The type and amount of radiation that you receive is carefully calculated during a number of therapy sessions. Over time, the abnormal cells die and the tumor shrinks. Normal healthy cells can also be temporarily damaged by radiation, but are able to repair themselves.
The goal of radiotherapy is to maximize the damage to tumor cells and minimize injury to normal cells.
What is fractionated radiotherapy?
The benefits of radiation are not immediate but occur with time. Aggressive tumors, whose cells divide rapidly, tend to respond quickly to radiation. Over time, the abnormal cells die and the tumor may shrink. Benign tumors, whose cells divide slowly, may take several months to show an effect.
Radiotherapy is split into a number of treatments called fractions that are given over several weeks. Delivering a small fraction of the total radiation dose allows time for normal cells to repair themselves between treatments, thereby reducing side effects. Fractions are usually given five days a week with a rest over the weekend. Therapy sessions often take less than an hour.
The radiation beams are generated by a machine called a linear accelerator. The beams are precisely shaped to match the tumor and are aimed from a variety of directions by rotating the machine around the patient (Fig. 1). There are several types of machines, but they all do the same things:
- Precisely locate the target (tumor, lesion)
- Hold the target still
- Accurately aim the radiation beam
- Shape the radiation beam to the target
- Deliver a specific radiation dose
Figure 1. Radiotherapy shapes the radiation beam to match the outline of the tumor and includes a margin of normal brain to prevent recurrence. The beams come from many angles and intersect at the tumor to produce a high dose. The red ring shows the high dose and each outer ring represents lower and lower doses.
What's the difference?
Delivers radiation at lower doses, over multiple days, and to larger areas. Treats a “margin” of brain tissue around tumors.
Delivers radiation at very high doses, a few times, to a small area. Benefit is its rapid fall-off giving a less dose to normal cells.
Doctors may recommend radiotherapy as a standalone treatment or in combination with surgery, chemotherapy or immunotherapy. Radiation may be given after surgery to stop the growth of tumor cells that remain. If eliminating the tumor is not possible, radiation can be used to relieve pain, seizures, or other symptoms.
Who is a candidate?
You may undergo radiotherapy if you have a:
- Primary brain tumor: glioma, glioblastoma, astrocytoma, lymphoma
- Benign tumor: acoustic neuroma, pituitary adenoma, meningioma, craniopharyngioma, glomus tumor
- Metastatic tumor: lung, breast, skin or other cancer that has spread to the brain.
Who performs the procedure?
Radiation oncologists are doctors who have special training in treating cancer and other diseases with radiation. The radiation oncologist works with a team that includes a surgeon, medical physicist, dosimetrist, radiation therapist, and oncology nurse.
The surgeon and radiation oncologist decide what techniques to use to deliver the prescribed dose. The physicist and the dosimetrist then make detailed calculations and set up the equipment. The radiation therapists position you on the machine and deliver the treatments.
The nurse provides care and helps you manage any side effects.
What happens before treatment?
Your first appointment is a consultation with a radiation oncologist. He or she will perform a physical exam and reconfirm your diagnosis the imaging studies (CT, MRI) and pathology reports.
They will discuss with you the best type of radiation treatment for your particular tumor or lesion, explain the treatment process, and describe possible side effects.
Once you've decided to go ahead with treatment, you will sign consent forms.
Figure 2. A thermoplastic mask is custom-fit to the contours of your face. The front and back pieces of mesh are secured to a U-shaped frame that attaches to the treatment table to hold the head still.
Step 1: create face mask
At your next appointment, a custom-made stereotactic mask will be made to fit your face exactly. It will be used during imaging and each treatment session to hold your head perfectly still. You will lie with your head on a cradle of mesh stretched between a U-shaped frame.
Next, strips of stretchy plastic are placed across your forehead, under your nose, and over your chin. You will be asked to bite a small piece of plastic with your front teeth. Next, thermoplastic mesh is dipped into a water bath, making the mesh very flexible. The mesh is placed over the face and allowed to conform (Fig. 2). You will be able to easily breathe.
Cold mitts help the mesh cool and harden. Creation of the mask takes about 30 minutes.
Step 2: simulation
Once the facemask is created you will undergo imaging scans, called a CT simulation, to carefully plan your radiation treatment.
It may be necessary to obtain a new MRI scan.
After the scan, the facemask is removed and you may go home. The doctors continue with step 3 (treatment planning), and you will return within a week or so to begin treatment.
Figure 3. Reflective balls are placed on the facemask prior to CT scanning. Markers are seen on the CT scan and help pinpoint the exact coordinates of the tumor or lesion.
Step 3: treatment planning Information about the tumor's location, size, and closeness to critical structures is gathered by the CT or MRI scan. Advanced computer software uses the scans to create a 3D view of your anatomy and the tumor (Fig. 4). Using the software, the radiation oncologist, surgeon, and physicist work as a team to determine the:
- appropriate target or targets
- radiation dose and number of treatment sessions
- number and angle of treatment beams
- size and shape of the beams to exactly match the tumor or target
Each individual beam is too weak to damage the healthy brain as it passes through on its way to the target. But at the intersection of all the beams, the energy dose is strong enough to destroy the tumor.
What happens during treatment?
About a week after the simulation you will return to the center for your first treatment. The nurse or radiation therapist will escort you to a holding room, where you may need to change into a gown.
Figure 4. The computer creates a 3D view of your anatomy. A treatment plan determines the number and angle of beams, the size and shape of the radiation beams, and the radiation dose.
Step 4: position the patient
After the radiation machine is calibrated and prepared for your specific treatment plan, you will lie on the table. The mask is placed over your face and secured to the table. If you have a head frame, it is secured to the treatment table.
Alignment lasers and x-rays help to position you correctly. Stereoscopic x-rays are taken and compared to the treatment plan. Any misalignments are corrected before treatment.
Figure 5. The facemask is secured to the treatment table and holds the patient’s head perfectly still and positioned in the treatment field. The machine rotates around the patient, aiming radiation beams at the tumor.
Step 5: deliver the radiation
The therapist leaves the room and operates the machine from the control room. The team watches you through video monitors and speaks to you over an intercom. The machine and treatment table move every so often to deliver radiation beams from one or more directions (Fig. 5).
The machine is large and makes a humming noise as it moves around your head. Its size and motion may be intimidating at first. It may pass close to your body, but it will not touch you. You do not have to hold your breath—just breathe normally. Treatment may take 30 minutes or longer, depending on the complexity of the target.
What happens after treatment?
After treatment the therapist releases the facemask from the table and helps you get up. The facemask is stored at the center for your next session. You will return each day at your scheduled time to repeat steps 4 and 5 until all fractions of the complete dose are delivered.
Recovery and prevention
Side effects of radiation vary, depending on the tumor type, total radiation dose, size of the fractions, length of therapy, and amount of healthy tissue in the target area. Some side effects are temporary and some may be permanent. Ask your doctor about specific side effects you may experience. General side effects may include:
Fatigue is common. You may feel more tired than usual for a few weeks following treatment. Fatigue can continue for weeks or months after treatment stops. Save your energy for important obligations and allow others to assist with chores or errands.
Make sure you get plenty of sleep, take a nap after treatment, and eat a balanced diet. Some patients may need to increase their caloric and protein intake because their bodies are working hard to repair itself. Some patients may notice a lack of appetite and a loss of taste.
Exercise and/or stretching can also help you to combat fatigue. A short, brisk walk can be rejuvenating and can give you a boost.
The skin at the areas where the radiation beams pass through may become slightly red and dry. This will go away after treatment stops.
To prevent irritation, use mild soap when bathing. Apply lotion daily, immediately after a shower, to those areas exposed to radiation. Monitor your skin throughout the entire course of radiotherapy.
Left untreated, skin irritation may lead to an infection.
You may experience hair loss in the treated area about two weeks after treatment begins. Hair will often grow back after treatment stops, though in some cases the regrowth may be incomplete.
To prevent further hair loss, use a mild shampoo (not harsh or fragranced) when bathing. Soft hairbrushes and low heat while blow-drying will also help prevent further damage to your hair.
Because areas exposed to radiation tend to sunburn easily, patients should protect those areas by applying sunscreen or wearing a wig, hat, or scarf.
Radiation causes tumor cells to die. The body's natural response to cell death or injury is swelling. Edema is extra fluid, or swelling, within the tissues of the brain.
If brain swelling occurs, it can cause headaches, weakness, seizures, confusion, or speech difficulty. It may also worsen the symptoms that were present before treatment. If you start to feel uncomfortable with headaches or any other symptoms, discuss this with your radiation oncologist.Steroid medication (dexamethasone ) may be given to reduce brain swelling and fluid within the tumor. Steroids should always be taken with food to protect your stomach and prevent nausea.
Steroids can also affect the normal bacteria in your mouth and cause a yeast infection called thrush – whitish patches on the tongue. Do not abruptly stop taking steroids. A tapering schedule is required to avoid withdrawal.
What are the risks?
In rare cases, radiotherapy may cause the center of the tumor to become necrotic (dead). Radiation necrosis can happen anytime, but it most often occurs 6 to 12 months after radiotherapy.
This dying tissue can become toxic to surrounding normal brain, and swelling may occur. Radiation necrosis may look similar to a regrowing tumor on an MRI scan. Special tests such as PET scan or MR spectroscopy/perfusion may help to tell between active tumor and necrosis.
However, sometimes these tests are not definitive. Treatment for radiation necrosis may include:
- Medicines that reduce inflammation, 5-LOXIN (Boswellia serrata).
- Hyperbaric oxygen therapy (treatment in an oxygen chamber) may be prescribed to help damaged brain tissue heal.
- A drug called bevacizumab (Avastin) may be given if other treatments are not effective.
- In some cases, surgery may be needed to remove the necrotic tissue.
What are the results?
After all radiotherapy sessions are done, MRI scans will be taken periodically so that your doctors can look for signs of response.
Several months may pass before the effects of treatment are visible. Some tumors may be completely eliminated with radiation. For others tumors the goal is to stop or halt the growth.
In some cases the tumor may not shrink, but still be considered “controlled.”
If you have questions, please contact Mayfield Brain & Spine at 513-221-1100 or 800-325-7787.
benign: not cancerous.
fractionated: delivering the radiation dose over multiple sessions.
metastatic: a cancerous tumor that has spread from its original source.
stereotactic: a precise method for locating structures within the body through the use of 3-dimensional coordinates.
target: the area where radiation beams are aimed; usually a tumor ormalformation.
reviewed by > Ronald Warnick, MD, Mayfield Clinic, Cincinnati, Ohio
Mayfield Certified Health Info materials are written and developed by the Mayfield Clinic. This information is not intended to replace the medical advice of your health care provider.