Radiotherapy -- the use of radiation in the treatment of
disease -- is an effective weapon in the treatment of many
forms of cancer. With the development of technical
refinements it is becoming increasingly successful.
Radiotherapy spread is used to control the growth and spread
of abnormal body cells. All living cells are damaged when
they absorb energy from X-rays and gamma-rays but growing or
dividing cells are damaged more easily than others. It is
because cancer cells grow more rapidly than normal cells
that they are slow to recover from the effects of radiation.
Radiation from X-rays and gamma-rays also destroys small
blood vessels on which tumour cells depend for nourishment,
so that following radiotherapy these cells are more
susceptible to the body's own natural defences.
surrounding normal tissue is more resistant to this type of
radiation, it is still easily damaged. More than any other
factor, damage to healthy tissue limits the doses of
radiation used in treatment.
TYPES OF RADIOTHERAPY
The many types of X-ray machines in everyday use differ in
the amount of energy or power of the X-rays that they
produce. If a tumour lies in or close to the skin it would
be unwise to use high-energy X-rays that would penetrate
deep into the body and damage normal tissues. Conversely,
there is no point in using low-energy X-rays to treat a lung
tumour, for example; the X-rays will not penetrate far
So there are superficial voltage X-ray machines
that are used to treat skin cancers, deep X-ray therapy
units that are used to treat tumours up to a depth of 10cm
(4in), and megavoltage or supervoltage machines that are
used to treat deep-lying tumours.
Because it is difficult
to produce very high-energy radiation from X-rays, gamma-ray
sources are sometimes used for this purpose. Cobalt or
caesium are the substances in most common use. A gamma-ray
unit consists simply of a quantity of a radioactive isotope
of caesium or cobalt encased in thick lead shielding. A
small aperture in the shielding is opened during treatment,
allowing a gamma-ray beam to emerge.
When powerful X-ray
and gamma-ray beams are used it is essential to take great
care to protect normal . tissue from exposure. The narrowest
possible X-ray beam which will encompass the whole of the
tumour is used.
Healthy areas are covered with lead
shielding and when this is technically difficult - on an
irregular surface such as the face, for example - a mould or
mask is specially made to fit over the entire region, with a
'window' cut out over the area to be treated.
It is also possible to give radiotherapy by placing
radioactive sources within the body. Needles, tubes, wires,
or tiny seeds of radioactive material may be implanted in
the tumour or placed in close contact. Because only
low-energy sources are used, the radiation emitted has only
limited penetration and normal tissues are unlikely to be
In the treatment of cancer of the cervix (neck of
the womb) and of the uterus (womb) tiny radium sources are
placed inside the upper part of the vagina and the uterus,
giving a much higher dose of radiation than would be
possible using other techniques.
The decision to begin radiotherapy treatment is usually
taken by a team of doctors, after the alternatives have been
fully discussed with the patient.
Treatment is planned by
the radiotherapist in conjunction with a radiation
physicist. Together they will map out the location of the
tumour on an X-ray film or a scan of the diseased area.
Using a special computer they will calculate precisely the
energy, dosage and position of the treatment beams that will
The beam positions, or 'fields', are marked
on the patient's skin using indelible ink or sometimes
tattoos. This permanent method of marking the skin is done
so that the patient can be accurately re-positioned under
the beam each time treatment is given.
usually spread over three to six weeks with some three to
five divided doses per week. The total dosage determines how
many tumour cells are destroyed, but dividing the doses
allows much better recovery of normal tissue and increases
the total dose that can be tolerated.
Most patients can be
treated as outpatients. The treatment is quite painless and
involves lying or sitting quite still on an X-ray table
beneath the radiation beam for a few minutes at a time, in a
special room that has walls shielded with lead and concrete.
The staff who work in radiotherapy departments are at
special risk from long-term effects of exposure to radiation
and are therefore not allowed to remain in the room while
treatment is being given. But the radiographer in charge
always keeps a careful watch over the patient through a
lead-glass window and is also able to talk to the patient
throughout the period of treatment.
The most common side-effect of radiotherapy is redness and
soreness of the skin overlying the treatment field. When
this occurs, patients are instructed not to wash or shave
affected skin for a few days until it improves, since soap
and drying with a towel make the soreness much worse.
the field includes an area of scalp the patient may lose
some of his hair, but it will usually grow back after
treatment has been completed.
Any exposure of the mouth,
gullet, stomach or intestines may cause loss of appetite,
dryness of the mouth, vomiting or diarrhoea. A high-calorie,
easily assimilated diet is often necessary until these
effects wear off. Blood counts taken during treatment are
used to monitor harmful effects or radiation of the bone
marrow. Radiation sickness is generally treated with
anti-nausea drugs and sedation.
A few types of cancer are highly sensitive to radiotherapy,
especially some tumours of the lymph glands and tumours of
the testes. Complete disappearance of tumours can be
expected within the treatment area, and complete cure is
often achieved by radiotherapy. Skin cancers are less
sensitive but will usually disappear completely following
treatment. Less sensitive still are the tumours that can
occur in the bladder, uterus, ovary, lung and breast.
Radiotherapy may be used after surgery, just in case any
tumour cells have been left behind. In lung cancer, complete
disappearance of the tumour following radiotherapy is
possible, but spread usually takes place at such an early
stage and to so many different parts of the body that
curative treatment with radiotherapy is not usually
possible, although it can relieve some of the symptoms and
the pain that are caused by the cancer.