Discussion and consent
A clinical oncologist or another appropriately trained professional should explain:
- the aim of treatment;
- reasonable alternatives;
- the proposed number of treatments;
- likely benefits;
- relevant short-term and long-term side effects;
- what may happen without the treatment.
Consent is a conversation, not simply a signature. You can ask questions and request more time where the clinical situation allows.
The planning appointment
For external-beam radiotherapy, most people have a planning CT. It is performed in the position intended for treatment. The scan provides the anatomical information used to outline the target and nearby organs and calculate the dose.
You may be asked to follow instructions about eating, drinking, bladder filling or bowel preparation. These help make the internal anatomy more consistent. Follow the information from your own department, as it varies between treatment areas.
Is my radiotherapy planning CT checking whether the cancer has spread?
Its primary purpose is treatment planning, not staging the cancer.
A planning CT is acquired in the treatment position and may use a scan range, breathing method, contrast timing or image settings chosen for dose planning. It is not necessarily equivalent to a diagnostic or staging CT interpreted to look for cancer throughout the body.
The planning images can occasionally show an unexpected finding, and the team will act if something important is seen. That does not turn the scan into a complete staging examination. Do not assume that a planning CT has replaced a diagnostic scan unless your team has said so.
If you are unsure, ask which scans established the cancer stage and whether any further diagnostic imaging is planned.
Positioning and supports
Radiographers may use cushions, a shaped support, a vacuum bag or a mask to help you remain comfortable and still. A mask is used for some treatments to the head, neck or upper body. It fits closely but should allow you to breathe normally.
Tell the team if pain, stiffness, anxiety or breathing difficulty makes the position hard to maintain. Adjustments are often easier before planning is complete.
Marks, tattoos and additional imaging
Small permanent dots or temporary skin marks may help reproduce your position. Not every treatment requires them. Photographs or surface-guidance systems may also be used.
MRI, PET or earlier diagnostic scans may be combined with the planning CT when they add useful detail. Image registration helps the team use information from more than one scan while recognising that the body may not be in exactly the same position.
When breathing-related motion matters, a 4D CT or another assessment may be used. The article on targeting moving tumours explains why.
Creating and checking the plan
After the scan, the clinical team outlines the treatment target and organs at risk. Planning specialists calculate how the dose can be delivered. The plan then goes through clinical and technical checks.
This work explains why treatment does not always start immediately after the planning scan. The interval is part of preparing treatment safely, not a period in which the scan is being ignored.
Highly focused treatments such as SABR may need especially detailed motion assessment, image guidance and dose checks.
Before the first treatment
Ask about medicines, skin products, transport, pregnancy precautions, implanted devices and what to do if you are unwell. Tell the team about any important change in symptoms or health since the planning appointment.
Some checks are repeated on the treatment machine before radiation is delivered. These images verify position and anatomy; they are not usually a new diagnostic scan.
Questions to ask
- What is the planning CT designed to show?
- Which scan established my cancer stage?
- Do I need to prepare my bladder or bowel?
- Will I need a mask or another support?
- How will movement be assessed?
- When should treatment start?
- Who should I contact if my symptoms change before then?
Knowing the purpose of each preparation step can make the process easier to understand and helps avoid confusing a treatment-planning image with a diagnostic staging scan.
