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Planning radiotherapy

See how you have a planning scan and what happens during your radiotherapy planning session.

The radiotherapy team plans your external beam radiotherapy before you start treatment. This means working out how much radiation you need to treat the cancer and exactly where you need it. Your planning appointment takes from 15 minutes to 2 hours.

You have a planning CT scan in the radiotherapy department. The scan shows the cancer and the area around it.

CT Scan.jpg

You may have a thin metal wire or small metal ball put into the anal margin. This is so the area clearly shows up on scans or X-rays. The doctor uses these scans to work out exactly where to give the treatment. This way it:

  • kills the most cancer cells
  • misses as much healthy body tissue as possible

Once you are in position the radiographers move the couch up and through the scanner. You need to lie very still. The radiographers leave the room and the scan starts. It takes about 5 minutes. You won't feel anything. The radiographers watch from the next door room.

Before the planning appointment you might also have other scans such as MRI scans or PET scans. Your treatment team can feed the other scans into the planning scanner.

Ink and tattoo marks

The radiographers might make pin point sized tattoo marks in the treatment area. These make sure they treat exactly the same area every day. They may also draw marks around the tattoos with permanent ink pen. This highlights the tattoos and makes them look like small crosses.

Radiotherapy tattoo marks
Radiotherapy treatment area marks.

The radiotherapy unit staff tell you how to look after the markings. The pen marks might start to rub off in time. If that happens, tell your radiographer. Don't try to redraw them yourself. 

After your planning session

It can take a few days or up to 3 weeks before you start treatment.

During this time your radiologists and doctors create your radiotherapy plan. They make sure that the area of the cancer will receive a high dose and surrounding areas receive a low dose.

Last reviewed: 
07 Jun 2016
  • Anal cancer: ESMO-ESSO-ESTRO Clinical Practice Guidelines for diagnosis, treatment and follow-up
    R. Glynne-Jones and others
    Annals of Oncology 2014. 25 (Supplement 3)

  • Neoplasms of anal canal and perianal skin
    D. Leonard and others. Clinical Colon Rectal Surgery
    2011 Mar;24(1):54-63.

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