| Germ Cell Ovarian Cancer -
Radiotherapy
Contents:
What Is Radiation Therapy?
Radiation therapy (also known as radiotherapy) is the use of different types of radiation to kill cancer cells. It is a local treatment, which means that it destroys cancer cells only in the part of the body being treated, and plays an important part in cancer treatment as 60% of all cancer patients receive radiation therapy at some time during the course of their disease.
Radiation damages the DNA (genetic material) in cells. It fights cancer cells by killing them when they try to divide, or reproduce. Cells do not always die instantly after having been exposed to radiation - it can take up to a month for cells to attempt to divide and then die. Therefore, the benefits of radiation therapy may not be seen until after the treatment is completed.
Cells that rapidly divide are very sensitive to the damaging effects of radiation. In general, cancer cells divide more quickly than normal cells and are therefore more susceptible to radiation induced damage than normal cells.
Damage To Normal Cells
Radiation therapy can cause damage to cancer cells and normal cells. Fortunately, normal cells are less sensitive to the damaging effects of radiation and are better able to repair the DNA damage than cancer cells. However, the damage to normal cells in the treated area can cause side-effects. Side-effects may be temporary if the damaged cells can be replaced or repaired, or permanent if they cannot.
The aim of radiation therapy is to kill as many cancer cells as possible, while sparing as many normal cells as possible from being exposed to radiation damage.
Radiation can be given externally or internally.
External Radiation
External radiation is the delivery of high energy radiation to a cancer, and is similar to having an X-Ray. High energy radiation is produced by different types of machines, the most common type being a
linear
accelerator. The types of external radiation used include:
When receiving external beam radiotherapy a patient does not become radioactive.
Internal Radiation
Internal radiation (otherwise known as brachytherapy) involves the placement of radioactive material inside the body, into or near the cancer to be treated. The radioactive material may be 'sealed', in the form of radioactive wires or seeds implanted in the body; or it may be 'unsealed', in the form of radioactive liquids which may be given
Intravenously, injected into body spaces or taken orally.
While the radioactive material is in the body, the patient is radioactive and must be isolated for the duration of the radioactive implant. This may be for a few minutes or for several days. When an implant is removed so is the radioactivity. For radioactive unsealed material the radioactivity must decay naturally or be passed out of the body before the radioactivity is gone.
While the patient is radioactive, there are special precautions that need to be taken to minimise radiation exposure to hospital staff and to visitors. In particular, children under the age of 18 and pregnant women must not be exposed at all.
Each patient is unique and radiotherapy must be tailored or planned for individual patients. Planning involves determining the best method of treatment, and how that treatment is to be delivered.
Position
Deciding on the position in which a patient is placed for treatment is an important part of planning for radiotherapy to be successful. The following factors need to be considered:
(a) the patient must be in a position that can easily be reproduced on a daily basis; and
(b) one that is comfortable so that the patient can easily remain still during the treatment, which is usually 10 to 15 minutes (sometimes immobilisation devices are needed).
A common position for gynaecological cancer treatment is lying face down on a special mattress designed to position the
bowel out of the radiation fields. Sometimes
oral radio-opaque
contrast (such as liquid
barium) is used to outline the bowel for this procedure and sometimes intravaginal radio-opaque
markers are needed. X-rays and measurements are taken of the area to be treated. Sometimes a
CT scan is also taken with the patient in the treatment position. Marks are drawn onto the skin using a semi-permanent vegetable dye to mark where the radiation beams will be focussed. Permanent tattoos may also be used to mark the radiation fields for long term radiotherapy.
Radiotherapy
The term for the dose of radiation given is Gray (Gy). The size of the dose of radiation given depends on:
 | the sensitivity of the cancer cells to radiation damage |
| the tolerance of the normal surrounding cells to radiation damage (that is, the dose limit above which the damage to the normal cells cannot be
repaired) |
| the size of the treatment area |
| the aim of the treatment (cure or palliation) |
| whether other treatments, such as chemotherapy or surgery, are being used. |
External radiotherapy is usually given as a course of treatments that can last from one day through to seven or more weeks, and usually does not require admission to hospital. Normal cells are better able to repair the DNA damage caused by small doses of radiation than that caused by large doses of radiation. Therefore, dividing the total dose to be given into many small doses (fractions) will reduce the damage to the surrounding normal cells and thus minimise the side-effects.
External radiotherapy is usually given once a day (Monday to Friday) which allows the normal cells time to repair the damaged DNA in between treatments. Sometimes more than one treatment each day is given.
Brachytherapy often requires admission to hospital.
The side-effects of radiotherapy treatment depend on
| the size of the radiation treatment fields for the area being treated |
| the dose of irradiation being given each day |
| the total dose delivered |
| whether other treatments are being used in conjunction with the radiation. |
Often side-effects do not occur at the start of a treatment, but tend to develop about halfway through a course of treatment. Not everyone will suffer from side-effects and their severity varies from person to person.
Common side-effects of treatment to the pelvis are:
| Feeling tired |
This occurs as part of a response to the work that the body has to do to repair the radiation damage. It may range from mild tiredness which may not affect your daily routine, through to needing a nap during the day.
| Loss of appetite |
This may be very mild, but it is important to maintain weight during treatment.
| Nausea |
This does not occur commonly unless chemotherapy is being used in conjunction with the radiation.
| Bladder irritation |
This may result in increased frequency of urination and there may be some associated burning or stinging. Increased fluid intake and the use of
urinary alkalinisers (an oral medication) can help minimise these symptoms.
| Bowel irritation |
This may result in increased wind and mild abdominal cramps, and can often progress to more frequent
bowel actions, which can become loose and develop into diarrhoea. Special diets and the use of anti-diarrhoeal medications may be required. The lower bowel (rectum/anus) may become inflamed and
haemorrhoids, if they are present, may become irritated. Local haemorrhoidal creams and
suppositories can ease these symptoms.
| Skin irritation |
The skin in the irradiated area may become red, dry and tender during treatment. There are creams and gels available to treat this.
| Hair loss |
There may be loss of pubic hair, which can sometimes be permanent.
| Fertility |
The ovaries are often included in a pelvic radiotherapy field, and this irradiation will result in infertility.
| Loss of oestrogen hormone production |
This occurs when the ovaries are irradiated and results in early menopause.
Hormone replacement
therapy will be required.
| Effects on sexual function |
The upper vagina is included in any pelvic treatment. The lining of the vagina becomes swollen and inflamed, which will result in sexual intercourse being uncomfortable and often sexual desire wanes. Extra lubrication is often needed. There is an increased tendency for scar tissue to form at the top of the vagina after treatment, which can result in narrowing and shortening of the vagina. This can make sexual intercourse and pelvic examinations uncomfortable. The use of vaginal dilators after treatment may reduce the effects of this scarring significantly.
|
