Prostate Cancer – External Radiation Treatment

External radiation, or radiotherapy, is defined as a non-invasive beam therapy that uses electrons, protons or neutrons as the beam. The oldest form is the electron beam radiation treatment (EBRT) and this is still the most commonly used prostate cancer treatment today.

A short history of radiation treatment

Radiation therapy as a treatment for prostate cancer was first used around 1915 in America. The first attempts used radium (a highly radioactive element) which, in many cases, killed the cancer however it also had a tendency to kill the patient as well. Next the Americans tried electron beam X-rays. Unfortunately these didn’t really have the power to irradiate through the skin and the tissue layers around the prostate gland however they did have the power to cause skin cancer in the area of the beam!

Things have improved dramatically since then though and by the 1980s scientists had developed the linear accelerator which increased the particle speed so that it could travel all the way to its target. It also made the beam easier to focus onto the prostate gland.

Newer versions of radiation treatment include:

• Intensity Modulated Radiation Therapy (IMRT)
• 3D-CRT (Conformal Radiation Therapy)
• Proton beam therapy
• Neutron-beam therapy although this is still in the experimental stages.

Types of Prostate Cancer Radiotherapy

Radiotherapy is the treatment for cancer of the prostate with radiation. This is most often as X-rays which pass through the body and kill the cancer cells in its path known as “external beam radiotherapy”. The alternative way to treat the prostate is from within the body using small radioactive sources known as “brachytherapy”. Brachytherapy is only suitable for a small proportion of men with early prostate cancer and with a suitable sized prostate gland. It has the advantage of slightly fewer side effects during the treatment but would not be so effective at curing more bulky prostate cancers.

Why undergo external radiation therapy?

There are three main types of prostate cancer treatments: radiation therapy, chemotherapy and surgery. The majority of patients the disease undergo prostate cancer surgery before any other treatment because removing the tumour drastically reduces the number of cancerous cells left in the body.

Radiation therapy is the best cancer of the prostate treatment that can follow on from surgery. The primary goal of radiation treatment is to irradiate a specific area i.e. the tumour in the prostate gland, with the highest amount of energy possible without damaging large areas of surrounding tissue and nearby organs. Electron beam radiation therapy is very good for this however the newer techniques of IMRT and 3D-CRT are even better.

The high energy electron beam damages the DNA in the nuclei of the cancerous cells. When these cells try to divide and reproduce the damaged DNA can not replicate properly and the cell ends up dying. Cancerous cells divide very rapidly and so radiation kills millions of cells in a relatively short period of time.

Unfortunately even though the electron beam is aimed specifically at the tumour cells some normal body cells also become damaged. Luckily however normal human body cells are slow to divide and so damaged prostate gland cells can repair themselves before they need to divide. Cancerous cells can’t though. This results in many more harmful cancerous cells dying than normal body cells. Even so some do die and it is this cell death that causes a number of the side effects commonly associated with radiation therapy.

External radiation treatment is often referred to as fractional radiation because small amounts are given to the patient every day for 5 out of 7 days a week. In addition this prostate cancer treatment usually last for around 5-9 weeks after which scans and PSA tests are performed to see if there has been any reduction in the size of the prostate cancer. The break in between sessions allows the body to recover and the normal body cells a chance to repair their DNA.

The side effects associated with external radiation treatment for prostate cancer are very similar to the early symptoms of the disease i.e. temporary incontinence, increased frequency of urination, difficulty urinating and a tendency to retain a small amount of urine after going to the toilet which can cause leakage. These urinary problems however are quite rare, as is any pain caused by the radiation treatment.

It is possible that some men may suffer from temporary impotence as well. Between 25-50% of men less than 60 years of age find that they have problems sustaining an erection following a course of treatment however this is normally short lived and they regain normal functioning after a few weeks.

External radiation therapy for prostate cancer is one of two methods by which cancerous cells can be irradiated from the body. The other method is internal and is commonly termed Brachytherapy. This method will be discussed in detail in the following ‘prostate cancer treatments’ page.