Radiotherapy for Prostate Cancer

External Beam Radiotherapy

An alternative treatment to radical surgery, Radiotherapy (“External Beam Radiotherapy“) aims to remove or restrict cancers by bombarding the affected area with high-frequency radio waves, also known as X-rays.

It has been known since their discovery that x-rays are harmful to biological cells, the sort that make up our bodies. If you have ever had an X-ray photograph, you will know that operators are outside the room, or behind shields when the X-ray source is operating. This is to limit the exposure, since it is known that x-rays cause cumulative damage to the body, and can themselves trigger cell mutations that lead to cancer.

In targeted x-ray radiotherapy, the presumption is that the risk of this is overtaken by the need to destroy existing cancer cells.

The principle is simple – high intensity focussed beams of x-ray radiation are aimed at the cancer tumour. The tumour cells are killed by the beam, as are the surrounding normal cells, but these can grow back and repair, whereas the tumour cells do not re-grow.

Clearly this procedure is not without risk and consequences. There are very sensitive other organs in the proximity of the prostate gland, specifically bowel and bladder, and it is a normal consequence that these structures will be damaged. This frequently leads to loss of bowel and bladder control, usually temporarily but sometimes permanently, and impotence due to damage or destruction of the cavernous nerve bundle that passes over the prostate gland.

Thus the side effects and consequences of Radiotherapy are very similar to those of radical prostatectomy .

The procedure usually consists of multiple daily sessions, carried out over a period of weeks, between 20 and 40 sessions depending on the assessment. This is to try and limit the damage to surrounding healthy tissues, and allow recovery of them between sessions.

Preparing for the procedure may involve an enema to evacuate the bowel and distance it from the target site, and filling the bladder to try and lift it out of the way.

As with surgery, pre-procedure pelvic floor exercises can help with this and help post-procedure recovery.

Stereotactic Radiotherapy

Focussed stereotactic abalative radiotherapy (SABR) is a relatively new treatment that uses a precision Cyberknife device to deliver high intensity very small area radiation. This requires fewer treatments, typically 5 over 10 days and causes much less damage to surrounding tissue. But it is not suitable for all cancer types, especially if you have a large prostate.

In 2025, this treatment is available in only very few centres, e.g. the Royal Marsden Cancer Charity.

Radiotherapy treatments may also be used when removal of the prostate leaves residual cancer cells, or a tumour has developed elsewhere.

Overall radiotherapy has an important place in the range of treatments available but comes with sometimes significant consequences.

Adjuvant Radiotherapy

If your radical prostatectomy treatment has not reduced your PSA levels to barely measurable, there may be some residual cancer left over, often in the prostate bed. You may be offered adjuvant radiotherapy, sometimes known as salvage radiotherapy, to kill off the last of the cancer cells.

The procedure is exactly the same as external beam radiotherapy with the same timescales and consequences. You may also be asked to undergo a PET scan to determine the exact position of any residual cancer.