External beam radiotherapy involves delivering large doses of conformal, or shaped, high-energy X-rays to the prostate using a machine called a linear accelerator, often shortened to linac. The most sophisticated technique is called intensity modulated radiation therapy (IMRT). Before the treatment starts, the radiation oncology team conducts a planning session called a simulation, which involves taking a CT scan and an MRI scan of the pelvis.
The simulation allows the team to identify the shape of the prostate and the normal surrounding structures to avoid (the bladder and rectum) and plan delivery of the radiation so that it’s as precise as possible. IMRT is given five days per week for approximately eight weeks. Each treatment takes less than 10 minutes to receive and is painless. Men are able to continue with their daily activities, including work, without interruption.