Treatments
External Beam Irradiation
Treatment Planning
In Australia the Radiation Therapist is a skilled professional, trained in both treating patients and in the planning and calculation of the treatment course. When a patient attends a planning appointment, planning Xrays and all necessary CT scans etc are done. (This procedure is described more fully in simulation.)
The Radiation Oncologist (specialist in charge) must then make a decision about how much volume to treat based on previous scans. After defining the volume of treatment on the X-ray or scan, the radiation therapy staff in the planning section then use a dedicated planning computer system together with knowledge of established practice to come up with a suitable method of treating the specific disease site.
Various numbers of radiation beams at different angles, with different beam shapes, beam weightings, beam energies and beam wedges are applied to obtain the best possible homogeneous coverage to the target volume without giving high doses to surrounding normal tissue. This optimisation process is greatly assisted by experience in the planning field.
Once a treatment plan is produced it must satisfy all the dose requirements which may include dose and volume limits on vital organs such as the kidney and/or spinal cord. Ultimately, the radiation oncologist must approve the plan.
The treatment plan must then be written up on a pre-prepared treatment sheet to accurately instruct treatment radiation therapists on the daily patient and machine set-up.
The treatment technique will often vary considerably from patient to patient due to a whole range of factors such as chance of cure, patient fitness, response rate, spread of disease etc, all of which are taken into account by the radiation oncologist.
Plans vary from the simple calculation of a single field of radiation to very complex planning routines used for some sites utilising CT and MRI data and planning multiple beams of special shapes on the planning computer.
The time taken to do these procedures varies widely. Some calculations can be done within an hour. Some may take days, especially when taking all the checking procedures into account.
Mould Room
Masks
Patients who need Radiotherapy to the head and neck region may require a visit to the Mould Room.
It is very difficult to keep still for the 10-15 minutes each day as required for Radiotherapy treatment, so an immobilisation cast (or mask) can be made to fit the patient’s head/face to help maintain a fixed position.
So the mask is a perfect fit, a plaster impression is taken with the patient lying in the exact position that is required for the treatment. Plaster of Paris bandages (as used to mend broken limbs!) are placed in warm water and then draped over the face, neck and top of head and smoothed out.
The mouth and nose are not covered – so the patient can still breathe! Cling film is used to protect hair, beard etc. As the plaster bandages begin to set, a little heat is generated, but is quite comfortable. The process takes about 15 minutes.
From the plaster impression (negative model), a plaster model of the patient is made and then a vacuum forming machine is used to mould a sheet of clear plastic over the plaster model and create a mask that will be a perfect fit for the patient.
On the second visit to the Mould Room the plastic mask, which has holes for the mouth and nose, is fitted on the patient to confirm the fit. Special brackets are riveted to the side of the mask. These brackets allow the mask to lock into a special part of the treatment couch. Once fitted the patient is in effect clamped to the bed in a fixed position, allowing very little movement of the head. The mask will be a firm fit but should not cause any discomfort. The mask is see- through, but holes can be cut out around the eyes for added comfort
This mask will be worn each time the patient attends for treatment as well as for the X-rays required for planning.
Shielding Blocks
At times the Radiation Oncologist may require to block out the radiation to certain vital structures within the treatment field. The doctor will mark on the X-ray the area required to be shielded and with a highly accurate computer driven hot-wire cutter, the relevant shape is cut from a block of polystyrene, then molten alloy (similar to lead) is poured into the mould.
After solidifying and cooling, the shaped shielding can be bolted to a perspex tray, ready for the patient’s treatment.
After being set up for treatment, the tray can be inserted into the machine, thus aligning the shielding block correctly.
Treatment
Currently at the Radiation Oncology Department at Sir Charles Gairdner Hospital we have three megavoltage linear accelerators each treating about 55 patients per day from 7:30am until 6:00pm. All machines can deliver 6MV energy X-rays and one can deliver a more penetrating 18MV X-rays which is more suitable for deep-seated areas e.g. within the pelvic area. Two of the machines can also deliver five different energies of electrons. Electrons are used for more superficial (closer to the surface) tumours such as skin cancers. One can be set-up to deliver X-rays to very small precise volumes in the head region. This is called stereotactic radiosurgery/therapy.
Usually treatment is given every day to patients, 5 days a week Monday to Friday for a set number of treatments. It is very important to attend every appointment wherever possible. Any unplanned breaks (ie other than weekends, public holidays and machine service days) must be approved by the Radiation Oncologist. If an appointment is missed this will need to be added on to the end of the treatment so the correct number of treatments is still given.
The number of treatments can vary from one to as many as 39. This will depend on the diagnosis and location of the disease and will be finalised at the planning appointment. All patients then receive a printout of their treatment appointment schedule plus other information about skin care and washing related to their particular treatment area. A nurse will ask whether they will need help with transport, accommodation if they are from the country, home help, wig fittings, diet, medications or any other concerns they have.
When patients come in for their treatment appointments the nurses are always available for any query related to the well being of the patient and their immediate family. If patients require extra help nursing staff may suggest they see a social worker.
Treatment machines have patients appointed every 10 minutes and are generally reasonably punctual. However unpredictable events such as machine breakdowns or emergency patients may occasionally result in a delay in receiving treatment.
During the actual treatment session the radiation therapists will set up the patient in the correct position using positioning lasers and field lights. They then must leave the room to deliver the dose. During this period of about a minute the patient is asked to keep very still and the therapists monitor the patient via closed circuit TV and intercom. The machine may move around the patient to various positions during the treatment but nothing will touch the patient. The machine emits a buzzing sound when the radiation is switched on.
During the treatment session, positional check images are taken either by film or by an electronic portal imaging system. These images provide the radiation therapy staff and the Radiation Oncologist with confirmation that the radiation beam is treating the same area each day to within 4 or 5 millimetres.
Images of the treatment area are compared to the planning or reference image. This can be done either visually by X-ray film displayed on light boxes or on computer screens by the use of matching software.
Slight adjustments will be made to the patient set-up measurements depending on the results of the matching process.
During treatment, patients will see their Radiation Oncologist or Registrar at least weekly, to check on treatment progress plus also any side effects that may arise from the radiotherapy. Patients should not hesitate to ask one of the nursing staff, if they are anxious about how their radiotherapy is affecting them, or if they experience any pain or nausea etc.
At the conclusion of the treatment course the Oncologist or Registrar follows up the patient at various intervals to keep a check on recovery and outcome of the disease. A letter will be written to the referring doctor or GP to explain the situation and any further management that may be required.
Ximatron (Simulator) and CT
The simulator is a diagnostic x-ray machine (like those used to x-ray bones) which can reproduce the movements and features of the linear accelerator. The CT or CAT (Computerized Axial Tomography) scanner is a large doughnut shaped x-ray machine that takes x-rays at many different angles around the body. These images are processed by a computer and produce cross-sectional images of the body. All patients will require a visit to either the Ximatron or the CT and some patients will require both.
It is very important that the patient lies in exactly the same position for each treatment. This position will be determined on the simulator/CT, and will take into account:
- comfort
- reproducibility
- accuracy
- sparing as much normal tissue as possible while delivering an optimal dose to the tumour.
The precise positioning of the patient is aided by the use of red laser lights. These harmless lasers are pencil thin and perfectly straight, and are used to make sure that the patient's body is straight and level on the treatment couch.
Some patients require treatment to their head or neck area. Normally, this is a very hard area to stabilise, and the use of a plastic mask may be required. This will be done in the Mould Room prior to your simulation appointment.
Simulator (Ximatron)
In order to determine the exact area of treatment, the doctor will refer to previous x-rays, pathology results, tests, scans and areas of discomfort or pain. Using this information, the radiation therapists will then localise this area of concern by using fluoroscopy. The fluoroscope produces an image similar to an x-ray, but it appears on a screen rather than an x-ray film. The staff can then adjust the position of the field while viewing the image on the screen. This procedure is painless, and is similar to having an x-ray picture taken. The only difference is that the patient may feel the couch moving slightly while the correct field position is established. Once the simulator has been positioned so that the field covers the area specified by the radiation oncologist, simulator films will be taken. The radiation therapists then use these films to plan and calculate the treatment. It is vital that the radiation therapists can reproduce the exact patient position from the simulator when treatment starts. In order to do this, a series of measurements will be recorded, and often a tiny, permanent mark (called a tattoo) will be made on the patient's skin to indicate the position in which the simulator film was taken.
Some treatments require only one or two treatment fields to deliver an acceptable dose. In this case, the radiation oncologist can approve the simulator film, and the treatment can be planned from this. In more complex cases the patient may need to have a planning CT scan.
CT Scan
Some patients will require a CT scan in order to assist the radiation oncologist in the localisation of the tumour, allowing them to target a precise volume of treatment around it. Although patients may have had previous CT scans it is necessary to have a ‘Planning’ CT scan as we need the patient in exactly the same position as they will have their treatment. The CT is located in the Radiation Oncology Department.
The patient will be given their list of appointments for their treatment after their simulator/CT appointment and is then free to go. The delay in starting treatment is due to the complicated planning process and/or availability of appointments on the treatment units.
High Dose Rate Brachytherapy
What is High Dose Rate (HDR) Brachytherapy?
High Dose Rate Brachytherapy is a time-tested and safe method that allows doctors to treat cancer with great precision and minimal trauma to patients. This method is called High Dose Rate because a high concentrated dose is delivered in a short time to the cancer.
The word "Brachytherapy" comes from the Greek "brachy" meaning short and "therapia," meaning treatment, referring to the placement of radioactive sources in or near the tumours.
Specifically, this internal procedure gives doctors and patients a significant advantage of applying a higher dose directly to the tumour while sparing the good tissue and surrounding vital organs. As a result, this treatment is quick, comfortable, and most often performed on an outpatient basis.
High Dose Rate Brachytherapy is as a sole treatment or combined with chemotherapy, surgery, or external beam irradiation.
What are the Benefits of HDR Brachytherapy?
Because High Dose Rate Brachytherapy allows doctors to safely apply a higher dose of radiation specific to each tumour, there are numerous benefits, including::
- A safe procedure because it limits undue radiation exposure.
- Decreased side effects.
- The treatment procedure is completed in approximately an hour with the specific radiation treatment taking about 10-20 minutes.
- After a brief rest time of 1-3 hours, patients usually can go home or return to work.
- In certain cases it may reduce the need to perform major surgical procedures.
- Can be performed in all accessible body sites.
- Iridium (I-192) is the radiation source used. It is easily available and is safely housed in a remote afterloader.
- Causes no radiation exposure to the staff.
- Patient is not radioactive after treatment.
- Safe and effective treatment for most cancers.
What can the Patient Expect During the Treatment?
While each treatment procedure is individualised to the patient's needs, the following are the typical procedures during a treatment.
- Because High Dose Brachytherapy is mostly an outpatient procedure, family and friends may wait in the waiting room nearby.
- Applicators, needles, or catheters are positioned in the relevant area.
- X-rays are taken to ensure proper positioning of the applicators, needles or catheters.
- The treatment team then calculates the exact dosage required for treatment using a state of the art 3-D computer model.
- After the planning and dose calculations are completed and approved, the treatment room is readied for the procedure.
- Our staff move to a nearby room to monitor the treatment and are in constant communication with the patient.
- Treatment starts when the system sends the radiation source to the tumour site (the patient will need to lie still during treatment so the tubes leading to the HDR machine are not dislodged).
- Total number of treatments is variable and may involve one session or several visits.
- The radiation source retracts into the system’s protective storage unit immediately after the treatment ends.
- The patient is able to leave after a brief rest.
Permanent Prostate Seed Implants
Treatment of prostate cancer with radioactive iodine seeds was introduced to Sir Charles Gairdner Hospital by urologist Prof. K Kaye1 in 1994. Sir Charles Gairdner Hospital was the first hospital in Australasia to offer this form of treatment and has trained many other Australian teams in the use of this technique. An implant team includes a urologist, radiation oncologist and a medical physicist. Since 1994, more than 120 patients have been successfully treated with this technique at SCGH.
Permanent prostate seed implant is a treatment option for selected patients with low risk prostate cancer. In this procedure tiny pellets containing radioactive iodine (I-125) are permanently implanted directly into the prostate under transrectal ultrasonic guidance (TRUS). These seeds are positioned so that the radiation is distributed throughout the prostate, and give off a low level of radiation for approximately one year. Since each seed only irradiates a small area, relatively little reaches the adjacent organs, including the rectum and the urethra. The seeds are smaller than a grain of rice, as shown in the image next to a five cent piece.
Approximately 6 weeks prior to the implant the patient will undergo a planning volume study. This is a transrectal ultrasound imaging study, which is performed in theatre under a general anaesthetic. These images will allow the medical physicist to determine the number of seeds required for the implant and where they should be placed.
The implant procedure takes place in theatre under a general anaesthetic. The implant procedure does not require a surgical incision; instead the seeds, which are contained in needles, are placed into the prostate through the perineum (the skin between the scrotum and anus). The needles can be seen on the ultrasound machine and guided to their final position. Once each needle is positioned the needle is withdrawn leaving the seeds in the prostate.
The day after the implant x-rays will be taken to assess the implant. Further to this a CT scan is usually performed 4 weeks post-implant to further analyse the implant.
Some advantages of permanent prostate seed implants:
- Seed implantation usually takes about one or two hours to perform. The patient usually leaves hospital the day after the procedure.
- Many patients resume normal activities within a few days.
- Recent clinical data shows a similar percentage of implant patients remaining disease free compared with either radical prostatectomy or external beam therapy.
Kaye KW, Olson DJ, Payne JT. Detailed preliminary analysis of iodine-125 implantation for localized cancer using percutaneous approach. J Urol. 1995;153:1020-1025.
Stereotactic Radiation Treatment
In the case of brain lesions a greater spatial accuracy than ‘conventional’ radiotherapy is required. In such cases increased emphasis is placed on:
Imaging: Over the decades 3D imaging has improved making it possible to superimpose various 3D images such as CT, MRI, PET, and angiography. Such imaging techniques enable greater accuracy and more precise imaging of the lesions and surrounding critical structures.
Dose accuracy: In conventional radiotherapy treatment dimensions are generally larger than 5cm. The dose accuracy for areas smaller than this is not ideal particularly when there are critical structures nearby. With stereotactic radiosurgery/therapy it is possible to treat much smaller areas with increased accuracy.
Immobilisation: As most abnormalities occur within the body, it is generally not possible to visualise the treatment volume on a daily basis. It is therefore necessary to ensure that the patient is placed in a reproducible and stable position on a daily basis. This is achieved with the use of immobilisation devices. In stereotactic treatments it is necessary to improve this immobilisation further, requiring a ‘ring’ to be positioned around the head attached by the use of four skull screws. These screws are attached to the head after local anaesthetic is administered. This can sometimes be painful.
What is the difference between Stereotactic radiosurgery and Stereotactic radiotherapy?
Stereotactic radiosurgery (SRS) is a way of treating brain lesions with a precise delivery of a single high dose of radiation in a one-day session. It is not physically surgical in that no incisions are made, but has a biological effect to the target tissues similar to that of surgery, hence the name. Some tumours require the treatment to be given over a period of days or weeks; this is known as stereotactic radiotherapy (SRT). The first day of SRS and SRT are very similar up to the point of the completion of treatment. Following SRS the head ring is removed and the procedure is complete. It would be impractical (not to mention uncomfortable!) to keep the head ring attached for a number of days so for SRT, head positions must be recorded prior to removing the ring. This by achieved with the use of a ‘bite-block’ that has attached markers that allow accurate localisation of head positions. This ensures set up to the exact same positions on subsequent visits without the head ring. On subsequent visits a custom made headrest and mask assist with immobilisation. It is very important that the bite-block is firmly located and that patients remain as still as possible – the less movement, the quicker the whole procedure!
How does it work?
Stereotactic radiosurgery works the same way as all other forms of radiation treatment. It does not remove the tumour or lesion, but it interrupts the DNA of the tumour cells. The cells then lose their ability to reproduce. In lesions such as AVMs – arteriovenous malformations (a tangle of blood vessels in the brain), radiosurgery causes the blood vessels to thicken and close off. The shrinking of a tumour or closing off of a vessel occurs over a period of time. For benign tumours and vessels, this will usually be 18 months to two years. For malignant tumours and metastatic tumours, results may be seen as soon as a couple of months as these cells are faster growing.
Intra-operative Radiotherapy for Early Breast Cancer (Intrabeam)
Intra-operative radiotherapy utilising the Intrabeam Device is a new method of delivering radiotherapy. It may be offered to women with early breast cancer who are suitable for breast conserving surgery. Intra-operative radiotherapy is not yet considered a standard treatment at Sir Charles Gairdner Hospital. Patients are therefore only able to undergo treatment with the device if they are registered on one of the two ethically approved Intrabeam clinical trials currently being conducted by the Department of Radiation Oncology (in close collaboration with the Breast Assessment Centre) at Sir Charles Gairdner Hospital.
For further information please refer to the section on Clinical Trials in Progress
Total Body Irradiation
As the name suggests, TBI is the treatment of the whole body using a Linear Accelerator.
This technique is most commonly used for the treatment of some forms of leukaemia.
Total body irradiation is given in addition to chemotherapy to:
- Suppress the body’s immune response so that you it will tolerate the infusion of donor cells.
- Increase bone marrow space for subsequent infusion of normal bone marrow by clearing tumour cells and normal white blood cells.
- Destroy a maximum number of tumour cells.
- Destroy tumour in sites that are difficult to treat with chemotherapy. This includes the brain, spinal cord and testis.
Rationale:White blood cells and tumour cells are very sensitive to radiotherapy and die whereas most normal cells are able to survive.
Technique: Treatment is delivered twice a day for 3 days. Treatments take place as far apart as possible – currently at approximately 6am and 6pm. Before each treatment the patient is given an injection to combat nausea and anxiety. They are positioned in the same position each day within a frame sitting on a bicycle seat. It is important that they stay very still for approximately 30 minutes for each treatment. As with other radiotherapy treatments nothing is felt.
Side effects: There are a number of side effects resulting from TBI. The patient should discuss these with the Radiation Oncologist.
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