Tomotherapy: The latest weapon against cancer in radiotherapy
A major innovation in radiotherapy, tomotherapy means this treatment can now target tumours specifically, while reducing the risks for healthy, neighbouring organs. Anthony Vela, a medical physicist at the François Baclesse Centre in Caen, takes us through this technique.
The advantages of tomotherapy, or helical radiotherapy, are the precision of the scanner and the ability to adjust doses of radiation. The radiotherapy is delivered by a piece of equipment which turns in a spiral around the patient, who lies on a table in the centre.
What are the benefits of this technique?
Anthony Vela: The main advantage of tomotherapy is that the intensity of the radiation can be adjusted. There are several different settings you can use. At the same time, the scanner with the moving table means areas of up to 1m60 long can be treated using a helical technique. The main advantage is that large masses can be treated with radiation in one go with this machine.
How does this technique allow the tumour to be targeted so precisely, reducing the risk for the healthy, neighbouring organs and delivering adjustable doses?
Anthony Vela: You can treat all tumours regardless of their location, whether it is the head, mediastinum or pelvis for example. The main focus here is to irradiate large areas. Tumours in the ENT sphere or the craniospinal area are generally treated with radiotherapy (because there are neighbouring organs which are sensitive like the spinal cord or the parotid glands for example). Patients can be treated from the brain down to the bottom of the spinal cord for example, and so the area targeted can reach up to 80cm long. This technology means a patient can be treated in just one session. For oro-facial cancers, lung cancer and certain types of breast cancer, cancer in the pelvic area, cancer in children, sarcomas in the arms or legs, and for full body radiotherapy, tomotherapy is particularly effective in treating these tumours if they have complex forms or are large in mass.
So what happens in this treatment exactly?
Anthony Vela: The different stages are actually not that different from traditional radiotherapy in fact. Once the patient knows they have been selected for radiotherapy treatment, he or she will be prepared for the treatment which involves taking different scans. This takes around two hours while all the material is prepared so that you are in the same position during all the sessions. Masks are used on five different areas for treatment of the ENT sphere, and casts are used for the mediastinal or pelvic areas. After the session, the patient can return home as the images will have been captured, and doctors will have a virtual picture of the tumour.
Next, the doctor will draw outlines around the images which need to be treated areas which need to be protected. At this point, the case is passed to medical physicists who will simulate the treatment. Dosimetric limits will be set for the mass, which means a minimal dose and a maximum dose for the organ undergoing treatment. There will therefore be maximum doses in place which must not be exceeded for certain sensitive organs to make sure there are no complications during or after the treatment. Once these parameters are set, the case is approved by doctors and the treatment can begin.
The difference between tomotherapy and other techniques is that imaging is done before every session. When the patient is prepared for treatment, his or her position is checked against these images. If there are any discrepancies these can then be adjusted while the patient is lying on the table. It is therefore possible to ensure that the treatment is carried out in the same conditions as in the preparation stage.
The session lasts around 20 to 25 minutes. No hospitalisation is therefore necessary except for heavier patients. It is standard practice to be taken to the hospital in an ambulance or using your own transport whatever the treatment, and return home straight after the 25 minute procedure.
Generally, patients undergo 30 sessions, which takes around six or seven weeks with sessions every day of the week.
Tomotherapy makes radiotherapy more widely available as it is suitable for patients who could not benefit from this treatment previously. The technique can therefore be used to complement more traditional treatments*.
Anthony Vela: We currently treat 25 patients a day at our clinic. We first offered this treatment around a year ago, and have treated 130-140 patients. I think it amounts to more than 4000 sessions, and so this machine is now well used. In France, there are around a dozen of these tomotherapy machines.
A report by David Bême and Florence Lemaire
* The first treatments took place in 2003 in the United States and in 2007 in France
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