Radiotherapy

About radiotherapy and the Radiation Oncology Division

About radiotherapy

The human body is made up of many types of cells and each one works in its own way to keep us healthy. Cancer forms when cells start to grow out of control. 

Radiotherapy is the targeted use of high-energy particles or waves to treat the cancer in a specific area of the body. It works by damaging the DNA of cancer cells, so they can’t repair themselves and eventually they die. Radiotherapy can shrink tumours or destroy them completely.

The six steps of your radiotherapy treatment

Your radiation oncologist will:

  • review your medical history
  • perform a physical exam
  • review your test results
  • explain your treatment plan or next steps  

The CT simulation is a scan of the part of your body that will be treated with radiotherapy.

You will be scanned in the position that you will be in for your treatments. Those images will be used to plan your treatment. 

Your radiation oncologist and other members of your care team will decide on the technical parts of your treatment plan.

This takes some time, so expect a delay between your CT simulation and the phone call telling you when you will start treatment. 

The first radiotherapy session usually lasts 30 to 45 minutes but, in some cases, a patient's first session lasts more than one hour.

Your radiotherapy technologists will take measurements and x-rays to make sure you are in the right position. 

You may receive more treatments like your first one, but they usually are shorter. 

Throughout your treatment, you will meet members of your care team regularly to track your progress. 

These checkups are a good time to ask your radiation oncologist questions.

Who do I talk to if I have questions?

Before your treatment starts


Please direct your questions to the patient liaison.

During treatment



Please direct your questions to the healthcare professionals you meet with in the hospital.

60 days or under since your last treatment


Please talk to a radiation oncology nurse.

More than 60 days after your last treatment


Please call the Cedars Cancer Centre at 514-934-4400 to book a follow-up.

You will be given the pamphlet "Radiotherapy at the Cedars Cancer Centre - A Guide to Preparing for Your Treatments" after your CT Simulation appointment. It has all the important phone numbers you might need during your radiotherapy journey. Please keep this pamphlet until the end of your treatment.